E30 Zone

Hi everyone,

recently took my M42 engine out to do some welding work on the car and since putting it back in I cannot get a spark at all.

It was running fine before I took it out, and I think I have re-connected everything properly but it would appear not to be the case!

I have power at the coil pack, its getting fuel, is turning over okay, DME relay and fuel pump relay working as they should.

Any ideas anyone?

Thanks in advance!

It'll be the crank sensor I'd have thought.

If the fuel pump's firing up when the engine is cranked, it unlikely to be the crank sensor, since it controls sparks and pump. Even with a partly faulty CPS, producing just enough output to activate the fuel pump, I'd expect at least some weak and mistimed sparks.
In fact, there are very few suspects if all in the OP is accurate - even if the plugs were on the coil pack in the wrong order, you'd still get sparks - just at the wrong time.
I suppose the ECU itself has to be a suspect, although failure of that is very rare, even if welding has been going on.

Relay mounting strip is inside my workshop door.

Thanks so much for your response.

The ECU is getting red hot with the ignition on, hot to the point I can't keep my hand on it so would suggest something is wrong with it?

Is there anyway to test if it's faulty?

Brilliant thankyou - when's good to pop round and pick it up...

If the ECU is getting really hot without the engine running, it does suggest it's faulty, Without crank sensor pulses all the drivers should be off, and it shouldn't be drawing much current at all.
I've put the wiring cover/relay mount on the window sill in the porch with the white PVC door.
Door's never locked, so just help yourself if no one's round.

Sorry still not been up to collect it- will hopefully pop up tomorrow.

Found out Ecu was getting hot because some wire wasn't connected to negative on battery and everything was on the whole time

Still no luck with getting a spark have had another go tonight...

Not sure if I'm imagining it but I think twice as I turned the ignition off I saw a spark, is that possible?
Secondly, I have power going to terminal 15 on each coil but tested resistance and readings were as follows:
On two coils facing engine I got a reading of 0.47 ohms and 0.49ohms and on the two coils facing wing, one flashed between OL, 000.0, 314.1, 0.799 and the other flashed between OL,000.0

I'm guessing this means the two facing engine bay are faulty?, am I replacing the bits with the terminals I've been testing with the wire running through to somewhere in the loom? Could this be the reason I've got no spark on Any of the plugs?

Any idea

Need more info. on this wire that wasn't connected properly to try and work out what damage that might have done.
The coil pack is four totally separate ignition coils built into one housing, so all should test identical, and there should be absolutely no continuity between them.
If the fuel pump is still starting up and running when cranking, there's not much that can be stopping sparks, other than duff parts of the ECU and/or coil pack. I've no idea if the ECU is sophisticated enough to protect itself if it encounters a shorted coil pack.
You could try the engine with just two coil packs connected and see if it shows any signs of running.

Hey thanks for all that info, think you nailed it with the duff eco comment- ran through the trouble shooter again and it led me to 'replace ecu'. Have ordered a new one- will it be a simple plug in and play or will the ignition etc have to be re coded for this ecu?

Many thanks

No coding or anything as sophisticated as that on any E30 bits. They all come from a time when life was much more simple!
Be sure to check out the coil pack before connected a replacement ECU. Just compare resistance readings between the four (should be) identical sections.
Spoke to your mum at the sausage fest. last night, and she said you still hadn't got it sorted.

Thanks everyone for all your advice, much appreciated. Problem now fixed- the ecu was the cause of the no sparking!