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Carburettor Problems
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Austin-sixteen-Cornwall



Joined: 01 May 2009
Posts: 26

PostPosted: Thu Jun 30, 2011 10:37 pm    Post subject: Carburettor Problems Reply with quote

Hi I am having great problems with my 1931 Austin Sixteen Burnham Saloon. As soon as the car is started petrol starts to leak from the carburettor. The engine then runs very rich and dies. I have cleaned the needle valve assembly as best I can but I cannot take it apart as it is pressed together. Any advice on what to try or what I can look at would greatly appreciated.
Thanks Arnold
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Churchill Johnson



Joined: 11 Jan 2011
Posts: 359
Location: Rayleigh Essex

PostPosted: Thu Jun 30, 2011 11:01 pm    Post subject: Reply with quote

Put a very small amount of fine grinding paste [jewellers rouge would be better if still available] put this onto the needle tip use a fine piece of wire putting it through the holes in the assembly then use a small piece of plastic tube pushed over the needle end and lap it in like grinding a cyl head valve in wash carefully after and blow out with an airline and retest this should do the trick repeat if ness, it would be better if you could obtain a new needle valve, make sure that the float is not damaged and got petrol in it which would make it too heavy and not do it's job shake it if not sure. .
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Austin-sixteen-Cornwall



Joined: 01 May 2009
Posts: 26

PostPosted: Thu Jul 07, 2011 10:11 pm    Post subject: Reply with quote

Thanks for that info - I have already tried to regrind the valve without sucess. Its very difficult to get the grinding paste to the right spot. I am considering getting the carb refurbished but have been quoted ten weeks turnround Sad

Regards Arnold
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Rick
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Joined: 27 Apr 2005
Posts: 22429
Location: UK

PostPosted: Thu Jul 07, 2011 10:40 pm    Post subject: Reply with quote

Is the float level incorrect, or possibly the float is sticking, causing it to flood? I had that with the Dodge, the float was catching (just) on the gasket very close by to it.

RJ
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baconsdozen



Joined: 03 Dec 2007
Posts: 1119
Location: Under the car.

PostPosted: Sat Jul 16, 2011 2:34 pm    Post subject: Reply with quote

T-Cut (especially the sediment in the bottom if its been stood a long while) is an excellent substitute for jewellers rouge.
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Austin-sixteen-Cornwall



Joined: 01 May 2009
Posts: 26

PostPosted: Sun Aug 21, 2011 11:48 pm    Post subject: Reply with quote

I am still no nearer resolving my carb problems - I have changed the needle valve assembly and it is improved - it does not leak when the petrol is turned on but it seeps out when the engine is started. I spoak to the previous owner yesterdsy and he suggested that the ethenol in the petrol these days may have affected the internal seals in the carb.
Has anyone else experienced this type of problem? Any suggestions greatfully recieved.

Thanks Arnold
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baconsdozen



Joined: 03 Dec 2007
Posts: 1119
Location: Under the car.

PostPosted: Mon Aug 22, 2011 4:00 pm    Post subject: Reply with quote

I've never worked on an Austin 16 so this might be well wide of the mark,but I did have a Mk2 consul where the pump developed too much pressure as someone had fitted a too strong spring in it.Untill the pump was changed it ran a lot better (and was more economical) with one of those pressure regulators plumbed in between car and pump,with the pump replaced (after the threads stripped) it ran perfectly without the regulator fitted.
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1229
Location: Chesterfield

PostPosted: Mon Aug 22, 2011 5:23 pm    Post subject: Reply with quote

baconsdozen wrote:
I've never worked on an Austin 16 so this might be well wide of the mark,but I did have a Mk2 consul where the pump developed too much pressure as someone had fitted a too strong spring in it.Untill the pump was changed it ran a lot better (and was more economical) with one of those pressure regulators plumbed in between car and pump,with the pump replaced (after the threads stripped) it ran perfectly without the regulator fitted.


High pump delivery pressure could be the problem. Pressure should only be about 2 psi normally though it does vary with fitment.
As well as a spring which is too strong a pump with the wrong arm can cause this by pulling the diapragm down further and thus loading the spring more.
I recall I did meet a similar situation where an SU electrical pump had been substituted for the mechanical one. SU pumps generally develop a higher feed pressure.
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Austin-sixteen-Cornwall



Joined: 01 May 2009
Posts: 26

PostPosted: Tue Aug 23, 2011 4:35 pm    Post subject: Reply with quote

Hi Thanks for those ideas. The car has an Autovac which means that the petrol is delivered under gravity from the Autovac container which is about 9 inches above the carb. so I dont think the problem is fuel pressure. I am going to have to investigate the carb. jets to see if they are properly sealed. This is big job as the hexagon sockets are all worn away. Any ideas on how to get them out? If I can get some new jets and seals will they be compatible with the 5% & 10% ethenol fuel ?

Any info gratefully received Arnold
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1229
Location: Chesterfield

PostPosted: Tue Aug 23, 2011 4:55 pm    Post subject: Reply with quote

Sorry, It never occurred to me that at that age an Austin would almost certainly have an Autovac. Just one question though, is the Autovac as originally mounted or might it have been raised for some obscure reason?
Since the jets in the carb will be submerged, I cannot see how they could possibly cause the carb. to leak. Run rich possibly if not seated properly, but not leak.
From just where is the leak evident? If it is above float chamber level it just has to be needle valve or float. I presume the float is not battered or dented and needing to rise higher to close off the needle valve.
There is usually a soft washer (often aluminium) under the needle valve head. Is that leaking or missing?
Jim.
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Nic Jarman



Joined: 05 Oct 2008
Posts: 1031
Location: Stoke by Clare, Suffolk

PostPosted: Wed Aug 24, 2011 10:00 am    Post subject: Reply with quote

I had a similar problem with my 8. It turned out to be float height but not just a quick tweek. I had relpaced the knackered float assy with one from a series E but used my float top to keep it looking right. It looked the same underneath but the pivot mount for the float was not the same height so the problem persisted. It was only when I got the vernier out that the discrepency was found. I gave it my best guess and it now runs quite well. Good luck.
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traction39



Joined: 19 May 2009
Posts: 399
Location: South Wales

PostPosted: Wed Aug 24, 2011 10:40 am    Post subject: Reply with quote

Which carb and where exactly is the leak coming from?
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