will fuel pump prime with 02 unplugged?

[Dj Buttchug]

Jim is correct. It wasn't until Motronic 3.x.x that the fuel pump primes prior to the key being in the "start" position. M42 runs on Motronic 1.7.

then how come both my late model cars prime before the engine starts....?

[irish44j]

Interesting....with the M10 and K-Jet, it would prime. (note that I'm still using the original dual-pump setup with the lifter pump, if that matters)

Ok, well I'll go with that being the reason then :)

[ForcedFirebird]

The fuel pump on an E30 only runs when the DME sees timing data from a rotating engine.

Jim is correct. It wasn't until Motronic 3.x.x that the fuel pump primes prior to the key being in the "start" position. M42 runs on Motronic 1.7.

[irish44j]

Just jumped the relay and the pump was cranking, so at least I know my M10 to M42 wiring connections are correct. I could hear the fuel coming up into the rail and such...

Still not a sound when the key is turned - no prime, no nothing. Guess I'll just have to see if anything happens tomorrow when I crank the engine.

[irish44j]

motronic needs to see a crank signal. When you key on engine off you should hear the pump prime the line.

M42 will run with no o2 sensor. It reverts back to base map.

That's what I thought. Doesn't do it though. hmm....

[Dj Buttchug]

motronic needs to see a crank signal. When you key on engine off you should hear the pump prime the line.

M42 will run with no o2 sensor. It reverts back to base map.

[bmwm42]

^ yup therefore it doesnt prime

[jlevie]

The fuel pump on an E30 only runs when the DME sees timing data from a rotating engine.

[irish44j]

Just doing my last checks before starting up the "new" M42 this weekend. Everything is hooked up EXCEPT the o2 sensor (I'm waiting for it to come in the mail).

In checking electricals (without trying to start it), with the car in the ignition position the fuel pump is not priming (or making any noise at all). Looking at the wiring diagram but not being an electrical guru, it looks like the fuel pump relay may not trigger unless the 02 sensor relay does?

Either that or the DME won't trigger the fuel pump relay if all the other sensors aren't registering.

Sound right?

Easy check would be if someone would unplug their o2 sensor at the socket below the battery tray, and then turn the ignition on and see if your fuel pump turns on or not....but I know that's asking a lot :)