fuel issue??

recently purchased mk1 gti as a non runner, changed number 2 fuel pump relay and started up straight away now when trying to start again it wont have it, could it simply be dodgy number 2 relay again? as it was 1 i had as spare or could i possibly have a fuel pump problem? how would i know if fuel pump is dodgy?

bump

You need to test the voltage at the fuel pump, should be around 12 volts when the pump is priming which will only happen for a few seconds when you first turn on the ignition, once the accumulator is up to pressure the pump stops running.

Check the fuel tank, if it has had a rotten filler neck problem the tank will be full of rust particles, change the tank, big job but the only cure if its a duffer.

The problem you will have if you have a sh1tty fuel tank is that the rust particles will be pulled into the fuel pump and accumulator, this will cause the fuel pump to pull more power than it should do to get fuel to the metering head so what happens is that the fuel pump relay (No 21) gets silly hot and melts the contacts inside it which can also bodge the fuse box in worst cases.

Change the fuel filter too because if the crap has benn pulled through, the filter will be full of debris stopping the fuel getting to the metering head.

Generally, fuel pumps either work or stop so when you turn on the ignition you will here the pump prime for a few seconds and the relay will click so that is the first thing to check, if you have got the common fault of 'weetabix' in the fuel tank, you have got to get it cleaned out.

Best wayis to get the fuel tank replaced but that is a job where you will need a car ramp because th rear end of the car all has to come off to get to it, big job but very satisfying when its done, just did mine on friday  :wink:

does the pump run when cranking? if not either the relay is dead, the pump, the fuse or you have lost the rev counter feed to the fusebox.

to check swap the relay #17/18 into the pump socket, that should make the fuel pump come on with the ignition. if car starts and runs fine then you have another duff fuel pump relay or the rev counter signal isnt making it to the relay