8v gti problem

Hi, I bought a mk2 golf gti 8v 1992 model about a year ago and it runs and sounds fine over 2500 revs but when at 850 rpm tickover it sounds loud and rough. I've changed the exhaust centre ans back but still the same and it's so embarrassing when you stop at a yellow line etc because of the noise. On my mk1 gti when you put the ignition on the fuel pump sounds then stops after 2-3 seconds but on this mk2 it stays on making that noise,so my question is - can it be the fuel pump and maybe it's over fuelling or something worst, ie the ecu?  :dontknow:
Many thanks for reading,Darren.

Any one please :dontknow:

I doubt it would be due to the fuel pump, the engine has a pressure valve and a return to the tank so whats not being used gets sent straight back. Your mk1 has the GSF aftermarket relay which primes… the original VAG one didnt, it only pumped when you turned the key

back to the issue in hand… has the car only just started doing this? do you know when the last time this was serviced ie plugs, leads, air filter etc?

it could be a number of things but to me it sounds like its running a bit rich which is why its rough at idle… have you checked the plugs to see what colour they are? if they're black and sooty you'll be running a wee bit rich, if they're white then its lean… if you have a haynes manual it will have some pics describing this.

where abouts are you located mate?

Matt

i've just had another thought but i dont know much about the later mk2's… I had a similar issue with my mk1, if its seriously missing, coughing, banging etc it could be the ignition amplifier

mine went on the way to Bournemouth, 15 mile into a 160 mile round trip and driving through Boscombe high street reving the nuts off to keep her running wasnt too amusing! was ok cold but once warm and the pcb expands is when the fun began lol

Cheers Matt for replying 8) The car has been doing this since I got and I thought it was just the back box was leaking,I've changed the plugs and the old ones looked fine.Maybe I should change the leads aswell but it runs really well, smooth and quiet when on the go with no splutters or back fires,It's just on tick over it sounds like a tractor,on tickover it stays steady at 850 rpm but so loud,then foot on accelerater to increase up to 1200 rpm it's nice a quiet.Also surly the fuel pump shouldn't be so loud.
I'm in Guernsey Channel Islads Mate.

yeah, even new ones you can hear easily when the cars not running mate so i wouldnt worry too much about that

check your rotar arm and dizzy cap to see if there's any build up or wear… after that it may be worth getting your CO checked down an mot station. I know its passed the last one but they do tend to be quite soft on the older classics (sympathy!) other than that i'd check the injectors and system pressure…

generally, if the fuel pump fails it will just stop working… if its got a bit of dirt in it or its failing it will usually start under fueling which you'll notice higher in the revs which is fuel starvation… your probablem sounds like the opposite.

if its none of the above then i'd possibly look at timing (check your vacuum advance pipe as some people lose these and adjust the timing to compensate), then maybe check the cam timing is correct… do you know if you have an after market cam in there of is it standard?

fuel pump on an 8v shouldnt be that loud at all, check the lifter pump is working. unplug the main pump and turn the key 1 click. also the pump should prime with ign on the mk2, it should not just run. if it is someone has bodged your pump wiring or fitted the wrong pump relay