E30 M3 Cutting out and driving me NUTS in the process HELP!

[rallyman1984]

Coasting along, and it just cuts out. usually with a rattle and the oil light, battery light etc... comes on as it dies, seems to take a while to start, sometimes taking 2/3 attempts to start.

Can hear fuel pump as it stalls, so i dont think it is fuel related.

Is it true that these engines cut power to the coil if there is a drop in oil pressure ? Possible suspect oil pump ? Are they common fault on S14 engines ?

ITS DRIVING ME MAD AHHHHHHHHHHHHHHHh

[Brianmoooore]

Only thing the oil pressure switch is connected to is the light on the dash. Any interference with the running of the engine would be dangerous in the extreme.
Could be lots of things, but is probably electrical. Connect a temporary wire to the ignition coil + into the cabin, connect it to a small 12V lamp, and connect the other side of the lamp to earth, and see if the lamp goes out when the engine cuts.

[rallyman1984]

Brian, what a good idea ! oh logical one.

[rallyman1984]

reckon there is any possibiltiy it could be the fuel pump relay (where ever it is) ??

[Brianmoooore]

You said you could still hear the fuel pump!

[rallyman1984]

i can. but maybe it cuts out so intermittently that i dont hear it stop/start its even got me doubting myself. !

[rallyman1984]

Right Brian, Theres a light rigged up, i'll try it today. i just hope i dont proper "break down"

[buster]

it maybe the coil.Try another one if you can.Has the ignition been left on for a long period of time without the engine running ?

[jpboost]

have you checked the conditoon of the dizzy cap/rotor arm? they'd be the first things I'd check. Also look at the leads.

mine used to do the cutting out thing, found it was a dodgy ecu. I only worked it out when it finally refused to start at all, and in my frustration banged the dash. The 'shock' through the ecu caused it to work again. got another ecu and it was all ok.

[rallyman1984]

Right boys. and girls.

Wired up a light to the + of the coil, and it stays on perfectly, then when it dies, it still stays on nice and bright, so that leads me to think it is fuel related.

Once it dies, it does start again, but it dies (as if its ran out of fuel) then it'll start and die a few times, but if i keep it well revved up e.g 3-4,000 rpm, it seems to be able to keep it running.
Now, I also need to mention, since ive had it, it's always been really lumpy and over fuely when it's cold, e.g have to rev it to keep it from fueling up. But now, it runs mint from cold, no lumpyness, no smell of fuel etc....

SO.... Is it a dicky fuel pump ? ..... cant be the relay surely, otherwise it wouldnt start/run would it.
Or is it a dicky fuel pressure regulator ?
Or is it possibly a fuel filter blocked ?? If there are any on an E30 M3 ???

Go on, post your views / opinions and help me !!

[Brianmoooore]

Could be any of them. Next easy thing to eliminate is the fuel pump relay, but you'll have to ask someone else where it is, 'cause I'm not familiar with the M3.
When you find it, pull it out of its base, and , with a short piece of wire, link together pins 30 and 87 of its base. This will (should) make the fuel pump run continuously.
Drive it like this and see what happens, but don't forget to remove the link when you stop or you will kill your battery.

[rallyman1984]

Where is the Relay on a normal E30. Cant differ too much from an M3.

[DaleR]

Sounds like a dry joint in the ECU?

[Brianmoooore]

Where is the Relay on a normal E30. Cant differ too much from an M3.

On a four pot it's under the wiring cover on the bulkhead, along with the main ECU relay and a relay for the lambda sensor heater, if fitted.

[rallyman1984]

right, update.

Light onto coil, coil is fine. so thats illimated.

Started up tonight, fine, then stalled.
Cleaned the pins on the Fuel pump relay (orange one) found it !!
and it restarted ran for a while then stalled. Now wont restart at all.
Just going to by-pass the relay, as brian suggested, and try that.

As it's turning over, i can hear the pump buzzing. (doesnt mean its putting any fuel up tho !!, as no really fuely smell etc...)

Will investigate fully tomorrow when it is light.

Still driving me nuts

[DaleR]

Bypass the relay with a bit of wire with 2 spade connectors on it, and drive it for a while, make sure you remove it when you have finished lol!.

If it still does it I recon its a dry joint in the ecu.

[LateM3]

I've experienced the same problems with my M3 , as previously stated it was a knackered ECU.
Try and borrow one to check first.

I managed to replace both relays, dizzy cap, rotor arm, both flywheel sensors, fuel filter, blue temp sensor and to no avail.

Dont throw parts at it like me My mate lent me his spare ECU and problem solved.

Bought a second hand unit from moseley motorsport

P.S. Lots of Good M3 info here = www.s14.net

[DaleR]

I've repaired a few bosch ecu's with great success!.