Am I Missing Something!

The engine is an Austin 10HP fitted to a Bristol 10 Tractor.
It now runs but very roughly.
The problem I have is that when priming the engine using the fuel pump
(AC T Type), fuel drips from the nozzle inside the carb(Zenith 30 vm).
This I also suspect is causing it to overfuel when running.
So far it has had a strip down, a good clean, rebuild with new
It is now on the bench with the fuel pump to test and it still does
I suspect its the float valve letting by but when removing the float
bowl and doing a manual test withslight finger pressure it does not
let by.
The float is okay and has been checked for leaks in warm water.
The Float valve gasket is the correct thickness.
Could it be Float, Float valve or even fuel pump pressure.
Am I missing something.
Any help or experince would be well appreciated on this matter.
Many Thanks
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My first try would be to get another red fibre washer between float chamber & carb, thus lowering the float height in relation to the main jet height. It costs little & might fix it!
If it does, I'd suggest that the float (or needle) is incorrect or worn, allowing the float chamber to fill too much. The float might be unsinking, but is it the right one?
Anyroadout, another washer should fix it.
J. Kim Siddorn, Regia Anglorum
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Reply to
Kim Siddorn
Is the relief valve in the lift pump stuck? Sounds like too much pressure into the float chamber. Try rigging up a temporary gravity feed tank (funnel on the end of a bit of plastic pipe) to see if it cures it.
Keep us posted how you get on.
Regards Dan
Reply to
Dan Howden
Hi Richard Nice crawler you've got there. I've got a 1939 bristol 10. Mines fitted with a jowett flat twin engine. I've had it rebored and a recon mag fitted so it now runs well but has been under a sheet now for 12 months, must get it finished this winter. Good luck. Regards, Gary M.
Reply to
gary millward
is the float pressing on the valve off center? is there a porous part in the carb casting? is the fuel pump delivering too much pressure as if the carb is designed for gravity feed?
just a thought. samm
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Last night I did the following further tests
No relief valve in fuel pump.(Checked after clean down)
Put another washer in - no good still doing the same
Ran it via gravity feed - leaked slightly
Also when sitting on the bench (Level) fed by gravity all okay.
Lift carb up from float end very slightly starts leaking.( as machine would not run on a level all the time)
Spoke to Burlen (Zenith) today and there suggestion is the float valve is worn.
More than likely okay when dead level but with a slight angle the float would push the vale of centre letting fuel by.
Have ordered a new one at a cost of =A37.00 plus vat.
Will let you know.
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Today all carb bits arrived.( Burlen give excellent service)
Out in the garage to fit the bits.
and you guessed it still leaked.
All I have not replaced is the float as they do not make them anymore.
Also tried packing a washer under the new one and it still does it.
Oh well.
Have to sit and look at this one a bit harder hoping it will sort itself out.
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Hmmmm - I was wrong in good company, but still sticking my neck out!
Perhaps the stroke of the pump is too great. How does it work - an arm bearing upon a cam or a plunger?
J. Kim Siddorn,
Reply to
Kim Siddorn

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