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TR2/3/3A Fuel Pump Diaphragm

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MLang99

MLang99

Freshman Member
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Just finished replacing my fuel pump diaphragm. Roughly 6 years and 20k miles.

It was advertised as being designed for modern fuels but I'm not convinced based on the look of it. Sure was easy to replace. 6 Screws and about 15 minutes.

Thoughts regarding the current ones being sold - will they hold up any better?
 

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I had poor success but then I was told that you have to pre-stress the diaphragm when you install it. I think that means you need to push on the lever as you tighten down the screws. Otherwise the rubber gives up.

Jerry
 
Might depend on where you got it. I put in one from TRF back in the 90's and it was still working fine when my TR3A got wrecked in 2005 (or was it 06?) on the way home from work. Bought another one in 2008 and it is still working fine in my current TR3.

But for some odd reason, the TRF kits are much more expensive ...
 
Good info! I will loosen it up and pre-stress the diaphragm before I drive it.

Thanks.
 
It came from TRF back around 2005. Just bought another new one from them. Same color but different markings and outline. It will be interesting to see how it holds up.
 
Regarding the rebuilding of fuel pumps, how necessary is it to replace the two one way valves? It appears that the failures are with the diaphram rather than the one way valves. The very old pumps had the one way valves held in with screws--easy to replace. But the later ones are held in with stamped edges. A real pain to change out.
Charley
 
I have never replaced the check valves and never had one fail per se, though I have had one of the staked versions fall out.

If they pass the 'suck & blow' test I just leave them alone.
 
Speaking of mechanical fuel pumps, after about 5 years of off and on running, but never reliably, and with a brand new Moss supplied A/C fuel pump with the primer handle, etc., I gave up and went to a Carter low-pressure electric pump. Car has never run better. But, I have been perplexed as to why the mechanical pump would consistently not supply sufficient fuel to the carburetors. Is it possible - and I am sure this sounds crazy - that over the 56 years since the cam was installed, the cam lobe has worn down enough that it is not sufficiently activating the pump lever? I can think of no other reason to explain the pump's failure to supply enough fuel. After all, it runs perfectly on the electric fuel pump with no other changes, so the fuel system and spark are fine. Thoughts?
 
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