More electrical gremlins or is this right ???

Hi all !!

Me again. My 1988 240 2.0l fuel pump never seems to stop when the ignition is on far enough to run the radio. Is this correct or is there something wrong with it ?

Thanks,
Jim,
'96 855-R (The Flying Wardrobe)
'88 245GL (The Melamine Wardrobe)

[cbyard]

This certainly doesn't sound right if you have the electromechanical injection system. The fuel pump relay should prevent the pump from operating at all unless the engine is turning- cranking speed is enough- as a safety and anti flooding precaution.

Could be someone has bodged a faulty fuel relay by linking it out, which would start the fuel pump as soon as the ignition was on (though I still wouldn't expect it to start in the auxiliary position) which would seem to be OK under normal operating conditions but is actually rather risky.

If you've got an electronic system- I don't know for sure- but other cars seem to run the pump continuously as soon as ignition is on and use an inertia switch to cut it out in the event of a collision. If the engine isn't running the electrically operated injectors stay shut and you don't flood the engine then.

Cheers

Chris

[Clifford Pope]

Mine runs for a second or two when I turn the ignition on (not auxiliary position) and then cuts out when it has presurised.I don't know how it detects that it is up to pressure - presumably the vacuum-operated return valve on the injector rail?If this became faulty, ie stuck open, then perhaps it would cause the fault described.
There seem to be several systems in use each with slightly different operating characteristics, and one person's description of how it works never quite seems to match one's own observations. eg I have heard that the static crank position, a matter of chance rest position, can cause the pump to run. But again, on mine the crank position has no effect.
I'd love to see some real expert comment, and assist the enquirer too of course.

Cliff Pope