[Mgs] MGA FUEL PUMP

Paul Hunt paul.hunt1 at blueyonder.co.uk
Thu Dec 17 05:50:53 MST 2009


Assuming it's pretty much like the original MGB pump:

If you have an SU pump then listening for clicking when turning on the 
ignition but before starting the engine is a perfectly valid test. Depending 
on how hot the engine was when last switched off it may click just a couple 
of times (cold) or for several seconds (hot). But if you turn the engine on 
within a few minutes of turning it off it may not click at all especially 
when cold. Note that some after-market types chatter all the time, 
regardless of engine demand.
If it doesn't click at all after having left the ignition off for several 
hours or overnight then the pump or its electrical supply is probably 
faulty. If it clicks, then it should stop, and only make a single click once 
every 30 secs or longer. If it clicks more frequently than that then either 
the float valves are leaking and it will eventually overflow, which if you 
have a charcoal canister make take some time to appear on the ground, or the 
non-return valve in the pump inlet is leaking. If it continues to click 
rapidly then either you are out of fuel i.e the fuel level is below the 
pickup strainer, the pickup pipe is perforated above the fuel line, or a 
float valve or the non-return valve mentioned above are stuck open. If rapid 
clicking stops and starts while the ignition is on but the engine isn't 
running that implies either very marginal fuel level or the non-return valve 
intermittently sticking. Note that some after-market types output excess 
pressure which will overwhelm the float valves and cause flooding unless a 
fuel regulator limited to 2psi is also installed.

If it clicks and stops as it should, then check delivery. Remove a fuel feed 
pipe from a carb (be aware it will spurt if the ignition has been on 
recently with SU and Moprod types), direct it into a container, and turn on 
the ignition. It should deliver at least one Imperial pint per minute, in 
practice closer to two, in a steady stream of pulses with minimal bubbles. 
Erratic pumping indicates pump or fuel level problems, lost of bubbles a 
leak on the tank side of the pump plumbing. Note that the delivery 
requirements apply to after-market types as well.

If all that is right then the only other thing running the engine is going 
to tell you is if there is a very intermittent problem with the pump or its 
electrical supply that only being operated for a long time may reveal.

----- Original Message ----- 
> What is the best way to check an original MGA fuel pump. 


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