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Colin Fairhurst

FLOODING CARBURETTORS

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I have recently fitted a new mechanical petrol pump to my TR2 and the carburettors flood over intermittently. I have since replaced the float chamber needle valves with Grose Jets but still get the intermittent flooding.

I am thinking that maybe the new pump is producing too high a pressure for the float chamber valves to cope with.

Does anyone know what the pressure should be?

Regards, Colin

 

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Have you fitted the pump correctly?  The pumping is done by the return spring, the cam only lifts the actuating arm which is then returned by the spring. I believe it is possible to get the arm on the wrong side of the cam so that the cam is pushing the arm down rather than lifting it up.........

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Thanks Rob.

I will check that but I was aware of that possibility when I fitted the pump, but it is still worth checking.

I was thinking that perhaps the return spring may be too strong. In which case swopping the spring from the old pump ( if that is possible) may solve the problem.

It would be useful to know what the pressure should be.

Regards, Colin

 

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I believe it should be between 1.5 to 3.5 psi Colin.

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Hi Rob,

I put a pressure gauge on the outlet of the new petrol pump and by operating the lever I got a reading of 5 lbs psi.

This afternoon I removed the pump and took the return spring out and did the same with the old pump.

Comparing the two springs with each other there was a considerable difference in there strengths so I put the old spring into the new pump and refitted it to the engine .

Again by operating the lever I got a reading of 2 lbs psi on the gauge which as you stated is probably the correct pressure.

I haven't yet had the opportunity to give the car a run but if that has solved the problem then obviously 5 lb psi is too much for both the needle valves and the grose jets.

Regards, Colin

 

 

 

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Yes 5 psi is certainly a bit too much for SUs and a quick web search shows several instances of people complaining of the same thing.  If it was a new pump perhaps you should let whoever supplied it know about this ?

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18 minutes ago, RobH said:

Yes 5 psi is certainly a bit too much for SUs and a quick web search shows several instances of people complaining of the same thing.  If it was a new pump perhaps you should let whoever supplied it know about this ?

I will do that.

Regards, Colin

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You might also consider raising this as a parts quality issue https://www.tr-register.co.uk/pqi

I personally think that flooding carburettors is a potential safety issue just like any fuel leak. If there are good and bad pumps out there, the members need to know.

Mick

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