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.

--
random signature text inserted here

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.

The mixture screw is connected to a bi-metal strip which alters the
mixture for the choke. It should never require turning by more than a
quarter of a turn in or out. If you try to richen the mixture by
screwing it too far in, you will bend the bi-metal strip which will
weaken the mixture. (and once bent you will never be able to set it
correctly)

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?

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.

--
*Do paediatricians play miniature golf on Wednesdays?

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

In article <ssmfqd$tvm$1@dont-email.me>,
Fredxx <fredxx@nospam.invalid> wrote:
> 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?

It's Doom. Very secretive about everything. Everyone is out to get him.

Thinking on the Jags I've had. Carb ones had the SU starting carb -AED.
They went injection after that.

Rover used the same unit. Either the Jag factory manual had full overhaul
details or the Rover one. Can't remember - but the other said just fit a
new one.

If I remember the AED from many years ago, it was a solenoid controlled by
a thermostat. Bodge was to add a switch, bypassing the thermostat control.

IIRC, Burlen have re-manufactured them, using original tooling. Won't be
cheap, though.

--
*I'm not a complete idiot, some parts are missing *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

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!
--
Cheers,
Roger

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 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 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 26/01/2022 01:17, Cursitor Doom wrote:
> 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.

The issue was simply an automatic choke fitted to an SU is a very rare
beast. Even Jags weren't fitted with them.

>> Did you sort out the issue?
>
> Haven't had the chance yet.

Good luck

On 26/01/2022 00:25, Cursitor Doom wrote:
> 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!

Development work at Crewe was done using LPG.

Cursitor Doom <cd@notformail.com> 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.
>

Eh? See section K5-13.

Tim

--
Please don't feed the trolls

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.

--
*PMS jokes aren't funny; period.*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

In article <ssq8ps$s18$1@dont-email.me>,
Fredxx <fredxx@nospam.invalid> wrote:
> The issue was simply an automatic choke fitted to an SU is a very rare
> beast. Even Jags weren't fitted with them.

Eh? Classic XJ engines used from the 50s to 70s - before they went
injection often had the SU extra starting carb system. My 58 3.4 MkI did,
as did my 78 XJ6. Both gave problems and had to be replaced. Rover also
used it too on some P5 and P6. They even made a kit to convert to manual
choke.

Rolls tended to make their own version. Presumably because of the poor
reliability of the SU one. (Although I'm not certain that starting carb
was made by SU)

--
*OK, so what's the speed of dark? *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

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.

--
*Pentium wise, pen and paper foolish *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

Dave Plowman (News) <dave@davenoise.co.uk> wrote:
> 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.
>

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.

--
*Ambition is a poor excuse for not having enough sense to be lazy *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

On 17/02/2022 15:16, Dave Plowman (News) wrote:
> 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.
>

Or hangs a handbag on it.