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Rootes75
Joined: 30 Apr 2013 Posts: 3825 Location: The Somerset Levels
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Posted: Mon Mar 22, 2021 4:41 pm Post subject: Carb or Timing? |
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So, got our Commer starting lovely now although even when warm she needs a quarter pull on the choke, it can be pushed in as soon as she fires and then she idles very nicely.
The main issue then is that give her any throttle and she pops and bangs a bit and the engine simply dies.
So, is this likely to be an issue with the fuel supply or the timing?
If it were timing would we not notice this when she idles, she doesn't miss a beat on tick over? _________________ Various Rootes Vehicles. |
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peter scott
Joined: 18 Dec 2007 Posts: 7121 Location: Edinburgh
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Posted: Mon Mar 22, 2021 4:54 pm Post subject: |
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I think I would look for blocked carb jets first.
Peter _________________ http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon |
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alastairq
Joined: 14 Oct 2016 Posts: 1955 Location: East Yorkshire
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Posted: Mon Mar 22, 2021 5:11 pm Post subject: |
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Does the distributor have a vacuum advance module?
Does the carburettor have an accelerator pump device? _________________ Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces. |
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22453 Location: UK
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Penman
Joined: 23 Nov 2007 Posts: 4765 Location: Swindon, Wilts.
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Posted: Mon Mar 22, 2021 7:02 pm Post subject: |
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Hi
Rick wrote: | Does the carb have an accelerator pump in it? Although I'd expect a problem with that to make itself more known under load rather than at idle.
RJ |
If it was a Ford the accelerator pump was the first place to look when the car won't start, or should I say strictly speaking it was the drivers right foot that was to blame. _________________ Bristols should always come in pairs.
Any 2 from:-
Straight 6
V8 V10 |
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alastairq
Joined: 14 Oct 2016 Posts: 1955 Location: East Yorkshire
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Posted: Mon Mar 22, 2021 9:13 pm Post subject: |
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Possible air leak creating weak mixture off idle? _________________ Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces. |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4109 Location: South Cheshire
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Posted: Tue Mar 23, 2021 7:50 am Post subject: |
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Do you have a Vacuum gauge that can be attached? simple and quick tests that can take loads of guesswork out of diagnosing these problems.
Dave |
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Rootes75
Joined: 30 Apr 2013 Posts: 3825 Location: The Somerset Levels
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Posted: Tue Mar 23, 2021 1:22 pm Post subject: |
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The carb is a Solex 40 FAIE, it has no air cleaner so is left open at the top aside from a lid that stops debris falling into it.
It does have the air retard pipe back to the distributor, it also has an air pipe attached that drops down into the engine next to the manifold.
I will take some photos at the weekend when I am next down the yard. _________________ Various Rootes Vehicles. |
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Rootes75
Joined: 30 Apr 2013 Posts: 3825 Location: The Somerset Levels
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peter scott
Joined: 18 Dec 2007 Posts: 7121 Location: Edinburgh
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Posted: Tue Mar 23, 2021 11:26 pm Post subject: |
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You might be able to tell whether a blocked jet was the problem by pouring petrol into the top of the carb as you open the throttle. If it revs rather than stalling then you've found your culprit.
Peter. _________________ http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon |
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Keith D
Joined: 16 Oct 2008 Posts: 1130 Location: Upper Swan, Western Australia
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Posted: Wed Mar 24, 2021 6:32 am Post subject: |
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If you pour petrol into the top of the carby with the engine idling, then rev the engine, be aware that if she "pops and bangs a bit' both you and the truck are going to get a nasty fright and maybe a burn or two.
Keith _________________ 1926 Chrysler 60 tourer
1932 Austin Seven RN long wheelbase box sedan
1950 Austin A40 tourer
1999 BMW Z3
Its weird being the same age as old people.
You are either part of the problem or part of the solution |
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Rootes75
Joined: 30 Apr 2013 Posts: 3825 Location: The Somerset Levels
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Posted: Wed Mar 24, 2021 8:03 am Post subject: |
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We have a replacement carb but the casing is slightly different from the original.
On the top the original has two threaded holes that the cover is fitted to, the replacement has no holes in the top of the casing so is obviously a little later and suitable for use with an air cleaner. _________________ Various Rootes Vehicles. |
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Rootes75
Joined: 30 Apr 2013 Posts: 3825 Location: The Somerset Levels
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Posted: Sun Mar 28, 2021 6:52 pm Post subject: |
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We try again.
Again, she will only start with choke even when she is warm. As soon as you put your foot down she backfires a couple times then dies completely.
We checked the advance/retard on the ditributor and that is working. It still sounds to us like a carb issue, the backfires burning off the excess fuel etc. _________________ Various Rootes Vehicles. |
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22453 Location: UK
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Posted: Sun Mar 28, 2021 6:58 pm Post subject: |
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alastairq wrote: | Possible air leak creating weak mixture off idle? |
This sounds like a possibility, my 2.5 Spitfire had a problem with terrible running, in the end I found that it was sucking in loads of air out of sight, underneath the carbs where they bolted to the inlet manifold. Someone had bodged the carb-manifold joint. If there are any vacuum take-offs from the inlet manifold, maybe try removing them and plugging the hole(s) to see if there's a problem there (Fords with the vacuum wiper motors can have issues if the pipe to the motor has a leak in it).
If with it running try spraying EasyStart or similar around the manifold and see if the idle picks up, suggesting an air leak.
RJ _________________ Rick - Admin
Home:https://www.oldclassiccar.co.uk
Videos:https://www.youtube.com/user/oldclassiccarRJ/videos
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ukdave2002
Joined: 23 Nov 2007 Posts: 4109 Location: South Cheshire
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Posted: Sun Mar 28, 2021 7:41 pm Post subject: |
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Rick wrote: | alastairq wrote: | Possible air leak creating weak mixture off idle? |
This sounds like a possibility, my 2.5 Spitfire had a problem with terrible running, in the end I found that it was sucking in loads of air out of sight, underneath the carbs where they bolted to the inlet manifold. Someone had bodged the carb-manifold joint. If there are any vacuum take-offs from the inlet manifold, maybe try removing them and plugging the hole(s) to see if there's a problem there (Fords with the vacuum wiper motors can have issues if the pipe to the motor has a leak in it).
If with it running try spraying EasyStart or similar around the manifold and see if the idle picks up, suggesting an air leak.
RJ |
As I mentioned previously, a simple old fashioned vacuum test will take a load of guesswork out.
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