M42 fueling problem

[rix313]

I've come to the conclusion that the reason my car cuts out after 40 seconds of running is because the fuel pump just stops after this amount of time then fails to work after. If left for a few minutes it then runs fine again until it stops and wont start.

Could there be a problem with the relay? Can these over heat and then fail? only to work again once cool?

Would it be possible to run a new wire to the fuel pump and have it actuated by a manual switch on the interior? Or will this mess up the ECU?

[Brianmoooore]

It's certainly possible for a fuel pump relay to behave something like as you describe, but I wouldn't recommend bypassing it on a permanent basis! It's only an ordinary relay, and not expensive!
Remove the back seat cushion, take off the inspection cover above the pump, and hook a small 12 volt bulb or LED to the fuel pump supply wires. The bulb should light when you start cranking the engine, and remain on all the time the engine is running.
Check if the bulb goes out before the engine cuts, or afterwards.

[rix313]

I have the interior totaly stripped as it's a track vehicle. From what I could hear the fuel pump stopped then the engine cut out about 5 seconds after. It then didn't make any noise after that until I left it and tried again.

I'll pop the loom cover off tomorrow and try a different relay and see how it goes.

Thanks Brian.

[Brianmoooore]

Experiment/deduction/conclusion, not random part swapping!

[rix313]

Managed to plug a light into the fuel pump connector and started to take a video of it. I'm not sure why but today, it ran and ran and ran. Showed no signs of previous behavior and the light stayed on.