Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding
it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding
it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars
with SU carbs fitted, and an auto choke facility implemented by a thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal
ones, and when the motor is cold a solenoid operates to open it up and
let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with
the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather
than too early.
Without further information any speculation is a bit pointless though
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding
it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding
it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars
with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal
ones, and when the motor is cold a solenoid operates to open it up and
let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with
the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather
than too early.
Without further information any speculation is a bit pointless though
If it is that sort of device, a short-term fix may be to wire a switch
in parallel with the temperature sensor. That would, in effect, convert
it to a manual choke - but only in the on/off sense rather than the progressive effect which you got in the old days with cable operated
chokes.
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding
it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
On 24/01/2022 10:25, Cursitor Doom wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:Completely irrelevant.
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the >>>> mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret. >>
Hardly. Some SU models had their automatic choke adjusted by their ECU.
Some had a bimetal spring.
Why be so awkward to someone who wants to help you?
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can
'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding >>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars
with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal
ones, and when the motor is cold a solenoid operates to open it up and
let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with
the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather
than too early.
Without further information any speculation is a bit pointless though
If it is that sort of device, a short-term fix may be to wire a switch
in parallel with the temperature sensor. That would, in effect, convert
it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated
chokes.
This document may help: >https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of
SU carburettor.
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
It is very relevant.
On 24/01/2022 10:25, Cursitor Doom wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley <fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the >>> mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
Hardly. Some SU models had their automatic choke adjusted by their ECU.
Some had a bimetal spring.
Why be so awkward to someone who wants to help you?
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the >>>>> mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
On Sun, 23 Jan 2022 22:01:17 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can >>>>> 'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding >>>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars >>>> with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal
ones, and when the motor is cold a solenoid operates to open it up and >>>> let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with >>>> the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather
than too early.
Without further information any speculation is a bit pointless though
If it is that sort of device, a short-term fix may be to wire a switch
in parallel with the temperature sensor. That would, in effect, convert
it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated
chokes.
This document may help:
https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of
SU carburettor.
Thanks, Roger. In the mean time, I've posted all I have on the subject
from the workshop manual here:
https://disk.yandex.com/d/bMitJ0e4YyvT6g
But I very much doubt it will help!
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, >>>>>> the
mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is >>>>>> quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of
secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the >>>>>> mixture is enriched largely by a butterfly valve in the main air
intake - that much is simple - but how that valve is controlled is >>>>>> quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of
secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I
mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>> quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort
of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU carburettors serving an engine with two banks of cylinders - possibly a
V8. That may narrow it down a bit - but not a lot!
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the
workshop manual, as the way this works is far from simple. I mean, the >>>>>>> mixture is enriched largely by a butterfly valve in the main air >>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>> quite complicated. I'll try to put up the relevant pages in the
morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of >>>>>> secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
We'll find out about the engine when an extract is shown from a 1990
workshop manual for a TSD4400, section K - Fuel system.
On Tue, 25 Jan 2022 23:17:36 +0000, Fredxx <fredxx@nospam.invalid>
wrote:
On 25/01/2022 20:57, Roger Mills wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>>> workshop manual, as the way this works is far from simple. I >>>>>>>>> mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>>>> quite complicated. I'll try to put up the relevant pages in the >>>>>>>>> morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort >>>>>>>> of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU >>> carburettors serving an engine with two banks of cylinders - possibly a
V8. That may narrow it down a bit - but not a lot!
I spotted that after my post. It seems there is a solenoid and a
standard bimetallic spring with a cam to set the idle speed.
The SU doesn't have a separate enrichment system to go wrong [1], so
this suggests:
1) The bi-metal coil isn't as effective as it was. It has relaxed so
relative positions has moved to indicate a hotter than actual temperature. >> 2) The fast idle cam is maladjusted
3) Some other effect that reduces engine efficiency, such as incorrect
ignition or camshaft timing.
All these things could require additional throttle. However as the
condition occurs after 30 seconds (assuming no over-enrichment to cause
revs to drop through chugging/missing) it does look like (1).
[1] I recall a Ford VV carb that over-enriched during the warm-up period
due to a damaged O-ring. Resulting in some chugging.
It would have been so much easier to have posted the type of carb. I
thought ones of this type were fitted to Rollers.
A crappy manual can be found here:
https://manualzz.com/doc/13968572/tsd4400-workshop-manual--rolls-royce-a-chapter-k
Not the similarity with the pic supplied by CD!
Why was CD so worried we might find out what he drives?
I don't just drive one car. And that manual's not much help as it
doesn't cover normally aspirated engines by the look of it.
On 25/01/2022 20:57, Roger Mills wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>> workshop manual, as the way this works is far from simple. I
mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>>> quite complicated. I'll try to put up the relevant pages in the >>>>>>>> morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort >>>>>>> of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU
carburettors serving an engine with two banks of cylinders - possibly a
V8. That may narrow it down a bit - but not a lot!
I spotted that after my post. It seems there is a solenoid and a
standard bimetallic spring with a cam to set the idle speed.
The SU doesn't have a separate enrichment system to go wrong [1], so
this suggests:
1) The bi-metal coil isn't as effective as it was. It has relaxed so
relative positions has moved to indicate a hotter than actual temperature.
2) The fast idle cam is maladjusted
3) Some other effect that reduces engine efficiency, such as incorrect >ignition or camshaft timing.
All these things could require additional throttle. However as the
condition occurs after 30 seconds (assuming no over-enrichment to cause
revs to drop through chugging/missing) it does look like (1).
[1] I recall a Ford VV carb that over-enriched during the warm-up period
due to a damaged O-ring. Resulting in some chugging.
It would have been so much easier to have posted the type of carb. I
thought ones of this type were fitted to Rollers.
A crappy manual can be found here:
https://manualzz.com/doc/13968572/tsd4400-workshop-manual--rolls-royce-a-chapter-k
Not the similarity with the pic supplied by CD!
Why was CD so worried we might find out what he drives?
On 26/01/2022 00:23, Cursitor Doom wrote:
On Tue, 25 Jan 2022 23:17:36 +0000, Fredxx <fredxx@nospam.invalid>
wrote:
On 25/01/2022 20:57, Roger Mills wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>>>> workshop manual, as the way this works is far from simple. I >>>>>>>>>> mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>>>>> quite complicated. I'll try to put up the relevant pages in the >>>>>>>>>> morning if time permits, but I'm not sure they'll help much! >>>>>>>>>
Yeah, why not - obviously the make and model of car is some sort >>>>>>>>> of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU >>>> carburettors serving an engine with two banks of cylinders - possibly a >>>> V8. That may narrow it down a bit - but not a lot!
I spotted that after my post. It seems there is a solenoid and a
standard bimetallic spring with a cam to set the idle speed.
The SU doesn't have a separate enrichment system to go wrong [1], so
this suggests:
1) The bi-metal coil isn't as effective as it was. It has relaxed so
relative positions has moved to indicate a hotter than actual temperature. >>> 2) The fast idle cam is maladjusted
3) Some other effect that reduces engine efficiency, such as incorrect
ignition or camshaft timing.
All these things could require additional throttle. However as the
condition occurs after 30 seconds (assuming no over-enrichment to cause
revs to drop through chugging/missing) it does look like (1).
[1] I recall a Ford VV carb that over-enriched during the warm-up period >>> due to a damaged O-ring. Resulting in some chugging.
It would have been so much easier to have posted the type of carb. I
thought ones of this type were fitted to Rollers.
A crappy manual can be found here:
https://manualzz.com/doc/13968572/tsd4400-workshop-manual--rolls-royce-a-chapter-k
Not the similarity with the pic supplied by CD!
Why was CD so worried we might find out what he drives?
I don't just drive one car. And that manual's not much help as it
doesn't cover normally aspirated engines by the look of it.
Yet has identical photos in your link. Are you suggesting your photos
weren't much help either?
Did you sort out the issue?
On 24/01/2022 16:01, Cursitor Doom wrote:
On Sun, 23 Jan 2022 22:01:17 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming >>>>>> off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can >>>>>> 'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding >>>>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as >>>>>> standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars >>>>> with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal >>>>> ones, and when the motor is cold a solenoid operates to open it up and >>>>> let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with >>>>> the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather >>>>> than too early.
Without further information any speculation is a bit pointless though >>>>>
If it is that sort of device, a short-term fix may be to wire a switch >>>> in parallel with the temperature sensor. That would, in effect, convert >>>> it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated
chokes.
This document may help:
https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of
SU carburettor.
Thanks, Roger. In the mean time, I've posted all I have on the subject
from the workshop manual here:
https://disk.yandex.com/d/bMitJ0e4YyvT6g
But I very much doubt it will help!
OK that isn't the one I had info on.
Junk the whole lot and fit fuel injection.
On Wed, 26 Jan 2022 00:35:48 +0000, Fredxx <fredxx@nospam.invalid>
wrote:
On 26/01/2022 00:23, Cursitor Doom wrote:
On Tue, 25 Jan 2022 23:17:36 +0000, Fredxx <fredxx@nospam.invalid>
wrote:
On 25/01/2022 20:57, Roger Mills wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>>>>> workshop manual, as the way this works is far from simple. I >>>>>>>>>>> mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>>>>>> intake - that much is simple - but how that valve is controlled is
quite complicated. I'll try to put up the relevant pages in the >>>>>>>>>>> morning if time permits, but I'm not sure they'll help much! >>>>>>>>>>
Yeah, why not - obviously the make and model of car is some sort >>>>>>>>>> of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU >>>>> carburettors serving an engine with two banks of cylinders - possibly a >>>>> V8. That may narrow it down a bit - but not a lot!
I spotted that after my post. It seems there is a solenoid and a
standard bimetallic spring with a cam to set the idle speed.
The SU doesn't have a separate enrichment system to go wrong [1], so
this suggests:
1) The bi-metal coil isn't as effective as it was. It has relaxed so
relative positions has moved to indicate a hotter than actual temperature. >>>> 2) The fast idle cam is maladjusted
3) Some other effect that reduces engine efficiency, such as incorrect >>>> ignition or camshaft timing.
All these things could require additional throttle. However as the
condition occurs after 30 seconds (assuming no over-enrichment to cause >>>> revs to drop through chugging/missing) it does look like (1).
[1] I recall a Ford VV carb that over-enriched during the warm-up period >>>> due to a damaged O-ring. Resulting in some chugging.
It would have been so much easier to have posted the type of carb. I
thought ones of this type were fitted to Rollers.
A crappy manual can be found here:
https://manualzz.com/doc/13968572/tsd4400-workshop-manual--rolls-royce-a-chapter-k
Not the similarity with the pic supplied by CD!
Why was CD so worried we might find out what he drives?
I don't just drive one car. And that manual's not much help as it
doesn't cover normally aspirated engines by the look of it.
Yet has identical photos in your link. Are you suggesting your photos
weren't much help either?
That's what I said earlier up the thread. But some folk here wanted to
see 'em anyway.
Did you sort out the issue?
Haven't had the chance yet.
On Tue, 25 Jan 2022 23:17:36 +0000, Fredxx <fredxx@nospam.invalid>
wrote:
On 25/01/2022 20:57, Roger Mills wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>>> workshop manual, as the way this works is far from simple. I >>>>>>>>> mean, the
mixture is enriched largely by a butterfly valve in the main air >>>>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>>>> quite complicated. I'll try to put up the relevant pages in the >>>>>>>>> morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort >>>>>>>> of secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
Well, he's shown us an extract from a workshop manual which shows two SU >>> carburettors serving an engine with two banks of cylinders - possibly a
V8. That may narrow it down a bit - but not a lot!
I spotted that after my post. It seems there is a solenoid and a
standard bimetallic spring with a cam to set the idle speed.
The SU doesn't have a separate enrichment system to go wrong [1], so
this suggests:
1) The bi-metal coil isn't as effective as it was. It has relaxed so
relative positions has moved to indicate a hotter than actual temperature. >> 2) The fast idle cam is maladjusted
3) Some other effect that reduces engine efficiency, such as incorrect
ignition or camshaft timing.
All these things could require additional throttle. However as the
condition occurs after 30 seconds (assuming no over-enrichment to cause
revs to drop through chugging/missing) it does look like (1).
[1] I recall a Ford VV carb that over-enriched during the warm-up period
due to a damaged O-ring. Resulting in some chugging.
It would have been so much easier to have posted the type of carb. I
thought ones of this type were fitted to Rollers.
A crappy manual can be found here:
https://manualzz.com/doc/13968572/tsd4400-workshop-manual--rolls-royce-a-chapter-k
Not the similarity with the pic supplied by CD!
Why was CD so worried we might find out what he drives?
I don't just drive one car. And that manual's not much help as it
doesn't cover normally aspirated engines by the look of it.
On Tue, 25 Jan 2022 23:45:02 +0000, Nick Finnigan <Nix@genie.co.uk>
wrote:
On 25/01/2022 18:27, Fredxx wrote:
On 24/01/2022 16:02, Cursitor Doom wrote:
On Mon, 24 Jan 2022 15:27:24 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <0kvsugtjdp858dsjuf7ul5h6ehrf2l2das@4ax.com>,
  Cursitor Doom <cd@notformail.com> wrote:
On Mon, 24 Jan 2022 09:12:26 +0000, Abandoned_Trolley
<fred@fred-smith.co.uk> wrote:
On 24/01/2022 01:28, Cursitor Doom wrote:
Thanks for the replies, guys.
There's not much I can do other than post a few pages from the >>>>>>>> workshop manual, as the way this works is far from simple. I mean, the >>>>>>>> mixture is enriched largely by a butterfly valve in the main air >>>>>>>> intake - that much is simple - but how that valve is controlled is >>>>>>>> quite complicated. I'll try to put up the relevant pages in the >>>>>>>> morning if time permits, but I'm not sure they'll help much!
Yeah, why not - obviously the make and model of car is some sort of >>>>>>> secret.
Completely irrelevant.
It is very relevant.
Nope. Counter-productive as will become clear in due course....
When do you think we'll find out? When is due course?
We'll find out about the engine when an extract is shown from a 1990
workshop manual for a TSD4400, section K - Fuel system.
Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo).
Any the wiser now? No? Thought not!
On Tue, 25 Jan 2022 18:28:46 +0000, Peter Hill <skyshac@yahoo.com>
wrote:
On 24/01/2022 16:01, Cursitor Doom wrote:
On Sun, 23 Jan 2022 22:01:17 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming >>>>>>> off too early is? I find cold starting easy enough and get a nice >>>>>>> smooth idle -but only for the first 30 seconds or so whereupon I can >>>>>>> 'feel' (as it were) the choke gradually coming off and the engine >>>>>>> starts to go all lumpy until it warms up properly following me holding >>>>>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as >>>>>>> standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars >>>>>> with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal >>>>>> ones, and when the motor is cold a solenoid operates to open it up and >>>>>> let some extra rich juice in to the inlet manifold. As you may have >>>>>> guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with >>>>>> the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather >>>>>> than too early.
Without further information any speculation is a bit pointless though >>>>>>
If it is that sort of device, a short-term fix may be to wire a switch >>>>> in parallel with the temperature sensor. That would, in effect, convert >>>>> it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated >>>>> chokes.
This document may help:
https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of >>>> SU carburettor.
Thanks, Roger. In the mean time, I've posted all I have on the subject
from the workshop manual here:
https://disk.yandex.com/d/bMitJ0e4YyvT6g
But I very much doubt it will help!
OK that isn't the one I had info on.
Junk the whole lot and fit fuel injection.
Seems a bit drastic! I'd be quite happy with a manual pull-out choke, >personally. And that would be a lot more do-able.
The issue was simply an automatic choke fitted to an SU is a very rare
beast. Even Jags weren't fitted with them.
Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo).
Any the wiser now? No? Thought not!
In article <v551vg9hfsdlghdnsk30jg3ioa0pm2i5j9@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo).
Any the wiser now? No? Thought not!
If you have a works workshop manual, they generally give very full
overhaul details. My Bentley one did - and the one I've seen for a Shadow.
Seems a bit drastic! I'd be quite happy with a manual pull-out choke, >personally. And that would be a lot more do-able.
Are the manual choke kits still available? Back in the 80s, I fitted my
Ford Escort with one, as the new-fangled automatic choke was sometimes a
bit 'iffy'. These days I think it would be rather difficult to find a
path through the bulkhead to route the cable, and a place to mount the
knob.
On Sun, 23 Jan 2022 22:01:17 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming
off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can >>>>> 'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding >>>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as
standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars >>>> with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal
ones, and when the motor is cold a solenoid operates to open it up and >>>> let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with >>>> the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather
than too early.
Without further information any speculation is a bit pointless though
If it is that sort of device, a short-term fix may be to wire a switch
in parallel with the temperature sensor. That would, in effect, convert
it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated
chokes.
This document may help:
https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of
SU carburettor.
Thanks, Roger. In the mean time, I've posted all I have on the subject
from the workshop manual here:
https://disk.yandex.com/d/bMitJ0e4YyvT6g
But I very much doubt it will help!
On 24/01/2022 16:01, Cursitor Doom wrote:
On Sun, 23 Jan 2022 22:01:17 +0000, Roger Mills
<mills37.fslife@gmail.com> wrote:
On 23/01/2022 19:00, Roger Mills wrote:
On 23/01/2022 15:17, Abandoned_Trolley wrote:
On 23/01/2022 15:01, Cursitor Doom wrote:
Gentlemen,
Does anyone know what the usual cause for an automatic choke coming >>>>>> off too early is? I find cold starting easy enough and get a nice
smooth idle -but only for the first 30 seconds or so whereupon I can >>>>>> 'feel' (as it were) the choke gradually coming off and the engine
starts to go all lumpy until it warms up properly following me holding >>>>>> it on fast idle for 5-6 minutes. The engine has SU carbs fitted as >>>>>> standard if that makes any difference.
It could make a lot of difference. I have had a few different Jaguars >>>>> with SU carbs fitted, and an auto choke facility implemented by a
thing called an "AED" or Automatic Enrichment Device.
It's basically a small electric 3rd carb sitting between the 2 normal >>>>> ones, and when the motor is cold a solenoid operates to open it up and >>>>> let some extra rich juice in to the inlet manifold. As you may have
guessed, the solenoid is dependent on the temperature sensor.
If your car is fitted with anything like this then messing around with >>>>> the carbs is a dead end.
However, I have only ever heard of them shutting off too late rather >>>>> than too early.
Without further information any speculation is a bit pointless though >>>>>
If it is that sort of device, a short-term fix may be to wire a switch >>>> in parallel with the temperature sensor. That would, in effect, convert >>>> it to a manual choke - but only in the on/off sense rather than the
progressive effect which you got in the old days with cable operated
chokes.
This document may help:
https://sucarb.co.uk/technical-auxiliary-enrichment-carburetter
It describes how the auto choke works on several different varieties of
SU carburettor.
Thanks, Roger. In the mean time, I've posted all I have on the subject
from the workshop manual here:
https://disk.yandex.com/d/bMitJ0e4YyvT6g
But I very much doubt it will help!
First warm it up with bonnet open and observe the cam and link. If that
is moving too soon it may be the restrictor in the "stove pipe" elbow.
The test is the very last bit in the manual, you won't have the required
flow meter to test it.
Never seen a bi-metal auto choke heated by exhaust gas before. Usually >electrical or coolant. Or they use a water heated wax capsule. But it
does mean 2 less water hoses, 4 fewer leaky hose connections and no
trapped air when filling the cooling system.
On Wed, 26 Jan 2022 15:36:28 +0000 (GMT), "Dave Plowman (News)" <dave@davenoise.co.uk> wrote:
In article <v551vg9hfsdlghdnsk30jg3ioa0pm2i5j9@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo).
Any the wiser now? No? Thought not!
If you have a works workshop manual, they generally give very full
overhaul details. My Bentley one did - and the one I've seen for a Shadow.
The pages I uploaded from the workshop manual are all they have to say
on the subject. They do provide some details on rebuilding/resetting
the mechanism to factory spec, but I was hoping for someone who might remember from back in the day what actually caused this issue and how
they rectified it. They don't tell you in those manuals what the
typical failure mode of any component is.
In article <gor2vg9ieej0cb9a3u8g45lrhlqn2k1e9h@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
On Wed, 26 Jan 2022 15:36:28 +0000 (GMT), "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:
In article <v551vg9hfsdlghdnsk30jg3ioa0pm2i5j9@4ax.com>,
Cursitor Doom <cd@notformail.com> wrote:
Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo). >>>> Any the wiser now? No? Thought not!
If you have a works workshop manual, they generally give very full
overhaul details. My Bentley one did - and the one I've seen for a Shadow.
The pages I uploaded from the workshop manual are all they have to say
on the subject. They do provide some details on rebuilding/resetting
the mechanism to factory spec, but I was hoping for someone who might
remember from back in the day what actually caused this issue and how
they rectified it. They don't tell you in those manuals what the
typical failure mode of any component is.
As I said, Rolls make their own, so you'd do better asking on a Rolls
forum.
With the SU one, the common failure was the thermostat. Many replaced it
with a switch inside the car - since any spare parts likely not easily available. Manual said to just fit a new or exchange unit.
With the SU one, the common failure was the thermostat. Many replaced it with a switch inside the car - since any spare parts likely not easily available. Manual said to just fit a new or exchange unit.
Remembering back to the early days of automatic chokes, I seem to recall
not all were as reliable / popular as they could have been.
Weren‘t kits available to convert to manual chokes? (Not SU carbs of course.)
We had a couple of cars ( an Escort and a Panda) with a manual choke and
they were fine.
In article <sulano$nse$1@dont-email.me>,
Brian <noinv@lid.org> wrote:
With the SU one, the common failure was the thermostat. Many replaced it >>> with a switch inside the car - since any spare parts likely not easily
available. Manual said to just fit a new or exchange unit.
Remembering back to the early days of automatic chokes, I seem to recall
not all were as reliable / popular as they could have been.
Weren‘t kits available to convert to manual chokes? (Not SU carbs of
course.)
They were for SU too. I fitted one for a pal to his P5B Rover.
We had a couple of cars ( an Escort and a Panda) with a manual choke and
they were fine.
Until someone unused to such things leaves it fully on.
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