Fuel pump runs all the time...?

[lancia4wd]

Hi,

Ok not all the time, but when the ignition is turned on it starts, not just when cranked.

Its a 390SE, flapper.

Help ?

Regards


Nick

[B-Reight]

Nick, the pump is switched by a pair of contacts in the AFM, these can fail so maybe someone has modified the afm. Any signs the black plastic cap has been prised off?

[CHJ]

The fuel pump does run all the time from when the ignition is on, on my '85 350i. The engine runs a treat though and always starts first time, so intend leaving well alone.

I guess the pump might wear out more quickly, but I can't see there being any other problems.

Chris

[B-Reight]

CHJ said:

The fuel pump does run all the time from when the ignition is on, on my '85 350i. The engine runs a treat though and always starts first time, so intend leaving well alone.

I guess the pump might wear out more quickly, but I can't see there being any other problems.

Chris

It shouldn't, the way it was designed the pump should run when the afm flap moves off its stop. Can't see much problem with it running like yours does though.

Edited by B-Reight on Thursday 4th March 15:30

[lancia4wd]

Thanks, so that means new or s/h AFM then ? Bugger. Yes the seal is broken on the unit.

Chris,

Running all the time, I guess the fuel pressurises the rails and then exits back to tank ? I think if you injectors are not perfect it leaks into cylinders as well, causing overfuelling / poor starting ???

If you have an accident, and the pump runs without engine running surely, big safety issue ?

Regards


Nick

[Wedg1e]

lancia4wd said:

If you have an accident, and the pump runs without engine running surely, big safety issue ?

The switch in the afm should turn the pump off when the engine stops, as it probably would in a big enough bump.
Some cars did get an inertia switch as an added precaution, however.

[Chauffeurdude]

If there is an inertia switch where is it likely to be fitted? Still having problems getting my 350i to run so thought worth checking that!

Also found a little silver flickswitch in glovebox on right hand side, any ideas? Cheers!!

[Pilo-Wedgebits]

Mine runs all the time even with the fuse and relay removed

[B-Reight]

Are you positive it is the fuel pump relay and fuse you're removing, they're not always in the right place they should be according to the relay location sticker as i recently spent half an hour upside down in the footwell trying to find my failed ignition relay!

[Pilo-Wedgebits]

I even traced the wire colours which matched the wiring diagram. That said with this fuse missing I lost spark (fitted to thick yellow wire)

[red tasman]

Chauffeurdude, people used to fit switches like that to use as an immobiliser, often connected to break the circuit to the coil or fuel pump.

Edited by red tasman on Thursday 4th March 22:39

[Wedg1e]

Chauffeurdude said:

If there is an inertia switch where is it likely to be fitted? Still having problems getting my 350i to run so thought worth checking that!

Also found a little silver flickswitch in glovebox on right hand side, any ideas? Cheers!!

The inertia switch was usually fitted to the firewall, in the engine bay, somewhere behind the engine.

[Chauffeurdude]

Thanks guys. Spoke to previous owner who doesn't know what switch is for. I did think of immobiliser etc as have done this trick myself but switching either way makes no difference. I did have a thread about this running problem before, will try to resurrect it as I desperately want to get the wedge going again having not being running since last May!! Partially my fault due to time/work commitments but really need it running now!! Cheers!!