Does the fuel pump work when the car is being started?

[1990m3]

I'm trying to trouble shoot a problem in one of my e30's and I am wondering if the fuel pump is supposed to be pumping while the motor is turning over (on startup) or if it just primes the fuel system when the key is in the "on" position and then starts working when the motor is running.

When I put a test light on the fuel pump it gets power when the key is in the "on" position and then the relay shuts it off after a few seconds. But the test light goes off when I am actually trying to start the car. Once the car starts the test light is on again and obviously the fuel pump is working.

Sometimes my car starts up poorly but it starts almost everytime. I think the fuel pump should be pumping while the motor is trying to start but before I rip apart the wiring harness I wanted to know if that is supposed to happen or if the motor just starts from the primed fuel pumped into the lines when the key is in the on position. If my wording is bad then I can re-word it, just let me know.

Thanks for the advice

Dave

[UofOm3]

it could be a dieing fuel pump, dave. my dads m3 is sidelined with that same problem now - just has not had the time to get around to fixing it. Anyway, i cannot give you quite the detailed answer that you want, but i can say that I think you are right in looking to maybe just replace the fuel pump and associated relay and cure all problems. This is one of the only things that can you leave on the side of the road in an e30 (dead fuel pump).

[1990m3]

well the car starts fine when it's cold and then when it's warm it sometimes does and sometimes doesn't start. When I started testing wires I figured it won't pump when the motor is turning over, that just doesn't seem right. I have to test my other e30 to see if it is the same way. This isn't MY m3 with the problem...between my dad and I there are 3 e30's that I have been trying to take care of.

[noro]

It's my understanding that on m3s the pumps don't run when the key is in pos 2 unless the car is running. So they should start pumping when you egage the starter.

[e30m3power]

IM pretty sure that when you turn the key to the ignition position that the fuel pump starts working. you can even hear it if you have the driver door open.

Is this not correct?

Thanks
Joey

[noro]

Originally posted by e30m3power
IM pretty sure that when you turn the key to the ignition position that the fuel pump starts working. you can even hear it if you have the driver door open.

Is this not correct?

Thanks
Joey

My 330i does that, but not the m3... maybe that's a problem with my car??? Can anyone lese confirm this?

the ICV starts working but it sounds much quiter and it's under the hood.