M20B25 no spark

[FinalD]

Until about a week ago, the car ran fine, first turn of the key and it'd fire into life. Now though it just cranks and cranks. The exhaust smells of fuel and I pulled a spark which had fuel on. So it isn't a fuelling issue, which means it is a spark problem.

The engine had a new dizzy cap and rotor a few months ago so I can't see it being them having failed.

The only things I can think it might be are the crank position sensor or the coil pack. As I swapped the engine out from another car I grabbed the coil and cps from that.

Tried both, still no spark and I'm not sure what to check next really.

If needed I'll replace the coil and cps but I'm fairly sure they are both fine and it is something else causing the issue, just don't know what.

[daimlerman]

You have tried laying a spark plug,connected to a h/t lead,on the rocker cover and cranking the engine to check for a spark?
You have checked for 12v at the green lead on the coil(ign on)?

[FinalD]

I've tried a spare spark laying on the rocker cover, yeah. I've not looked for a 12v on the +V...partly as I'm not sure my multimeter is actually any good, it's likely older than 90% of the zone members.

I'll give that a go though, it's something I thought about just now but wasn't sure on.

It's odd that it has suddenly stopped working, battery does have a decent charge too.

[daimlerman]

12v bulb between the lead and terminal on the coil will work just as well.

As you have fuel,my next suspect would be CPS.

[FinalD]

I tried the meter on the terminal and absolutely nothing, not even a mild flick. Which suggests that it is something prior to the coil, like the CPS. Annoyingly I have two, one from the knackered engine and one from the running engine, tested the spare one and still no joy. Could quite easily be that both are past it at 143k and 145k each.

The annoying thing is that because the car hasn't been run properly it has never gotten hot (in the past few years), so the whole 'dies due to heat' argument is shot down. Not cheap for a replacement either by the looks of things.

Looking at RealOEM...never realised that the module above the glovebox was for the ignition system/pulse generated by the crank sensor. That is plugged in by the way...I will have a check on the wiring around there though, ensure that nothing is messing up. The unit's case doesn't need to be earthed by the hanger bracket by any chance does it? Currently it is floating in the footwell as I'm looking at dash light problems.

[daimlerman]

This RHD?

Module 'above glovebox' is ABS....

Try GSF for a CPS,I paid about £40 a few months back.

Should run fine with the engine ECU dangling.

[Speedtouch]

Check the DME relay. This switches the power to the ECU.

http://www.e30zone.net/e30zonewiki/index.php/DME

[FinalD]

This RHD?

Module 'above glovebox' is ABS....

Try GSF for a CPS,I paid about £40 a few months back.

Should run fine with the engine ECU dangling.

It is RHD. Ah ok, RealOEM confused me then.

ECP were £50-£80, BMW £95, will have a look at GSF.

Check the DME relay. This switches the power to the ECU.

http://www.e30zone.net/e30zonewiki/index.php/DME

Interesting. I'll have a check with that in a bit then, cheers.

[Speedtouch]

The DME (Main) relay is the white 5-pin one shown on the left in this photo:

[Grrrmachine]

As you have fuel,my next suspect would be CPS.

You wouldn't get fuel if it was a CPS issue.

I tried the meter on the terminal and absolutely nothing, not even a mild flick.

Meter will give confusing an incorrect readings due to the lack of load - you need to use a test bulb.

Aside from that, I can't really offer advice as to where the issue really lies though

[Speedtouch]

Also check the engine to body earth strap is in place and secure. If you have a multimeter, check that is is giving a continuity buzz, or resistance reading of close to zero ohms between the engine and the body or battery '-' terminal.

[FinalD]

I tried swapping the DME/Main relay with one from the touring, again, nothing, I haven't tried shorting it just yet though (as mentioned in the wiki link). I'm not ruling out a problem with it as there is every chance that the spare parts I have are also knackered, I always bear that in mind with used parts.

Impressively I have access to loads of tools, but no test bulb things, at least not that I've seen. I'll have a rummage in the tool chest and cupboards later to be sure though.


What I don't understand is that since it last ran, all I've done is:
a) fix the diff speed sensor wire (one of the two had snapped)
b) sent brake fluid all over the floor when bleeding (kind of didn't do a join up properly)
c) removed the dash
d) removed the stereo wiring
e) removed the live and switched live for the aftermarket boot aerial

All the dash wiring, including earths, is connected up properly (will have yet another check over this later) and I've not touched anything in the engine bay. I tell a lie, I did, I moved the airbox and coolant expansion tank out of the way when fixing a brake line leak at the ABS unit. These have since been returned to their positions and all wiring reconnected.

I'll run through the checks you guys have suggested later on tonight and report back my findings.

[daimlerman]

As you admit to removing the dashboard,is the link plug in the green wire still present and correct?

[Grrrmachine]

As daimlerman says, fiddling with the dash almost always causes issues with the green wire:

http://www.e30zone.net/e30zonewiki/inde ... Green_Wire

[Speedtouch]

As above, check that green wire where it runs behind the glovebox. Also, what age M20B25 is it - pre-facelift, or facelift? Some early pre-facelift 073 ECUs were reknowned for failing.

Also, do you have an OBC or immobiliser?

[FinalD]

As above, check that green wire where it runs behind the glovebox.

I'll have to have a look at that tomorrow, sounds plausible!

Also, what age M20B25 is it - pre-facelift, or facelift? Some early pre-facelift 073 ECUs were reknowned for failing.

It's a Feb '88 car, E reg. I have the touring which is an F reg (don't recall build year/month), tried that ECU and same results so shouldn't be that.

Also, do you have an OBC or immobiliser?

No OBC (although in theory wiring for it, but the car works...well, did). It has an immobiliser, Thatcham approved jobbie, when it is active you don't even get instrument cluster lights, cuts all power to things basically.

Cheers for the ideas so far lads.

[Speedtouch]

E-reg was the changeover year between Motronic 1.1 and 1.3, so an ECU from an F-reg car won't necessarily work with it - what is your ECU number, e.g., 0 261 200 173.

[FinalD]

Both are 173, the engine is from the F reg but it was the same as the E reg...which is handy. The engine has been running fine on the original ECU.

[Brianmoooore]

Totally confused after skimming through the above, but I didn't see any mention of what car we're dealing with, and not sure if you've done what I've written below or not!
Find a 12 volt bulb and connect it between the + terminal of the ignition coil and clean earthed metal, such as the earth terminal on top of the RH suspension turret, with the ignition switched on.
Does it light?

[FinalD]

It's a 1988 E30 325i cab.

Haven't tried the bulb on coil test, will see if I can find a 12V bulb for testing today. Have tried the multimeter with no movement on the needle at the coil. Have tried two coils and neither have a signal (using the meter) and I know both do/did work so it should be something pre-coil, hence the mention of the green wire by others.

[FinalD]

Oh. My. Fookin. Gawd.

So I removed the wire that someone said was for the OBC in another thread because I have no OBC, thought nothing of it.

Today, figured 'just make sure that wire doesn't make any difference' plugged in, turned key...wnker, fookin works. Looked at the cable, turns out it has been butchered and the wires soldered together then recovered in tape fairly well so wasn't obvious it had been done.

Cheers for all the help guys, typical that it was something so damn simple though.

[Speedtouch]

Probably butchered for an aftermarket immobiliser. Anyway, congratulations on getting it to run again!