Car cuts out - fuel pump electrics?

March 28, 2022, 07:01:31 PM

Wonder if anyone has any experience with an issue I’m currently having where the engine cuts out on my ‘86 Gti. I’ll be driving along normally when the rev counter suddenly drops to zero as the engine dies, but lights and MFA etc still have power. Occasionally it restarts straight away, but normally I prod the fuse box for a minute or two before it will work. I noticed that the fuel pump relay felt pretty warm, but not burning hot.

When I checked under the bonnet, the battery negative lead (including the earth) was loose - could this cause the fuel pump to cut out, without (noticeably) affecting anything else? I tightened the connection to the battery and the Golf ran home fine, but it could be pure luck…

A bit of history: I had some issues last year with the fuel pump electrics - initially the relay went, then (after a second breakdown) the garage noticed a problem with the earth wiring behind the fuse box. Both of these issues had the same effect as above, i.e. they led the car to cut out. After the wiring was fixed and the car ran well - until now!

The negative lead for the battery may be a red herring (but so could my prodding of the fuse box)! Unsure if it’s a new wiring problem or perhaps the root cause is an issue with the fuel pump itself, or something totally different. Either way, I’m sure it will be fun finding out

One other thing I noticed - I think the problem is worse when the car is warm, it has never failed to start or cut out immediately after starting, it always lets you drive a few miles away from home first haha

Thanks in advance for any thoughts!

Re: Car cuts out - fuel pump electrics?

Reply #1 – March 28, 2022, 07:51:32 PM

An 86 will be k-jet so there’s a lot of potential reasons. If you check out my k-jet resources page linked in my signature (doesn’t show on a mobile) you I’ll find more info and a trouble shooting chart.

If it’s hard to restart after warm that would suggest fuel pressure controlled by the WUR warm up regulator.

For now I’d see how it goes since doing the earth strap and keep your fingers crossed that was it.

Mk3 and mk4 battery leads are a good upgrade and worth doing if you have access to a scarp yard.

Re: Car cuts out - fuel pump electrics?

Reply #2 – March 28, 2022, 08:04:37 PM

Thanks Eddypeck!! Hadn’t seen the link as I’m always on my phone, but will defo check it out shortly. Sounds very useful and relevant for me. Appreciate your input, as always - thanks again