Wont start...

[tomson]

The car in question is a work collegues 1991 320i M20.

It just wont start and run, I have given him guidance on things to check and he has a haynes manual which hes followed some of the things to check in it but still no luck.

He has checked the following things -

Good strong spark on all 6 plugs
C192 plug/wiring is all ok (new plugs also fitted)
2.5bar in the fuel feed line (rises to 3bar when cranking)
Fuel pump runs when linking pins 30 & 87
Power is getting to the fuel pump ok

The car is cranking fine but it just wont start but if he unplugs the fuel pump it starts and runs for a couple of seconds before dying, reconnect the pump electrics and it wont start!
He fitted a 2nd hand fuel pump just before Christmas as the old one packed up...

Any suggestions please???

[tomson]

Thanks willnz, I did tell him to pull/replace the relay and feel if its clicking so will ask tomorrow, though its the fact it starts when you cut power to the pump that baffles me...

[tomson]

Another thing, has it started since he replaced the fuel pump?

Yes its run fine for a month and then just wouldnt start last week...

[tomson]

He has checked the CPS today at the pins on the ECU plug and has zero ohms there, should have 500-600ohms IIRC? Does that mean CPS is shot and its the problem?

I forgot he told me this!

[rix313]

Thanks willnz, I did tell him to pull/replace the relay and feel if its clicking so will ask tomorrow, though its the fact it starts when you cut power to the pump that baffles me...

My iS did this not long ago. Sadly I don't have the answer to what caused it. Mine seemed to sort it's self when I took the connector off, gave the electrodes a clean with some rag then plugged it back in again.

[tomson]

Yup, pins 47 & 48 is what I told him, hes a qualified electrician so I know he knows how to use his meter!

We knocked up an inline fuel pressure gauge last week and he put it in the fuel feed line and there is 2.5bar there with the ignition on and it rises to 3bar when cranking the engine over on the key so I assume the rise in pressure means its running?

I've had fuel pump issues in my cars in the past and Im sure I remember a good pump will spray fuel everywhere with the main feed line removed. Steve's sprays out a couple of inches and drops straight off to which I immediately said your pump is fecked hence we made the gauge, which gives 2.5bar which is what it should be!
Having just bought a 2nd hand pump if it is the problem he wants to buy a new one but at £100+vat we need to be sure first!

[tomson]

He did the bulb on the pump thing and it lit up the same when cranking & when not.
I'll ask about the plugs in the morning

[tomson]

I'm mistaken, the test light on the fuel pump only lights up when cranking and the plugs were wet when removed after a failed starting attempt.

Normally the pump should prime for a couple of seconds when the ignition is switched on and its not doing this but there is 2.5bar in the line and it is lighting a bulb when cranking....

[tomson]

He has also just told me that the car is trying to start, not really a cough or a splutter, but the note from the engine does change as if its catching but not enough to fire and start properly but still starts with the pump disconnected for a few seconds then dies.

It's got to be fuel or air related I think!