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

--
random signature text inserted here

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.
--
Cheers,
Roger

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.
--
Cheers,
Roger

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.

In message <aa81vgtv6e79usv45nvi551ckasu3va7s2@4ax.com>, Cursitor Doom
<cd@notformail.com> writes
>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.

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.
--
Ian

In article <IcW1iADuUQ8hFwej@brattleho.plus.com>,
Ian Jackson <ianREMOVETHISjackson@g3ohx.co.uk> wrote:
> >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.

There was definitely a manual choke conversion kit for V-8 Rovers fitted
SUs and their starting carb I remember fitting one to a pal's P5B.

The Rolls has bigger SUs, though. IIRC 2" rather than the Rover 1 3/4"

Late SUs (HIF) didn't move the main jet like earlier types - they had a
cold start valve on the side. All to allow them to comply with emission
laws.

I'd ask Burlen Fuel systems if cold start bits can be fitted to the 2"
carb. As regards the linkage and knob. you'd be on your own, for such a
low volume car.

The P5B conversion still comes up from time to time on Ebay, etc.

--
*According to my calculations, the problem doesn't exist.

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

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.