*Solved* Tricky no start 318i

[BristolE30]

Hey zone

Me and a friend have just purchased a nice Laguna green 318i. It ran great... for about 20 minutes at which it start hesitating and stumbling under load and then stalling. Started up again, got home and let it cool. Now she’s a non starter completely.

Things we’ve tested:
DME relay from working car, no change
CPS at the plug and ecu pins. Reading 560ohms
Fuel line off and cranking. Lots of fuel coming out
Spark from the coil... here is where it gets weird. It will intermittently spark. First time it works, then it won’t spark at all. Been trying last couple days and it just sometimes does, sometimes doesn’t.

What are we missing here? Clearly the issue is no spark but why. Ignition coil readings are fine and we even swapped it out with known working coil and still no luck.

What would cause the ignition coil to intermittent spark?

Our last port of call was gojng to be try another ECU

Any help appreciated

[Brianmoooore]

Check the 12 volt supply to the coil by connecting a 12 volt lamp between the coil + terminal and the battery negative connection on the strut top.
It should light at full brightness when the ignition is turned on, and stay lit while cranking, although it might flicker slightly while doing so.

[BristolE30]

Check the 12 volt supply to the coil by connecting a 12 volt lamp between the coil + terminal and the battery negative connection on the strut top.
It should light at full brightness when the ignition is turned on, and stay lit while cranking, although it might flicker slightly while doing so.

Yes we did try voltage to coil with meter. All good

[BristolE30]

Are there any other reasons for intermittent spark? Could CPS still be broken despite good ohms readings

[Brianmoooore]

High resistance CPS is dud. Normal resistance CPS may be dud.
You can't measure the reduction in resistance as a result of a few shorted turns, and an open circuit CPS may be intermittent, but there must be some activity from it if the fuel pump switches on.

[BristolE30]

*Solved!*

Issue was some small fraying on the CPS cable. The crank pulleys had worn it down and the wires were shorting on the unsheathed earth wire!!

So if you’ve got a non start, no spark, but still have fuel, dont write off the CPS! Check the wires!

[Brianmoooore]

So if you’ve got a non start, no spark, but still have fuel, dont write off the CPS! Check the wires!

You still had some spark. If you had no spark at all, you wouldn't have fuel either. The sparks you had may have been few and probably at the wrong times to even make the engine fire, but without the pulses for the EU to integrate, the pump relay wouldn't switch on.
The damage is repairable, as long as you waterproof things with self amalgamating tape.

[BristolE30]

So if you’ve got a non start, no spark, but still have fuel, dont write off the CPS! Check the wires!

You still had some spark. If you had no spark at all, you wouldn't have fuel either. The sparks you had may have been few and probably at the wrong times to even make the engine fire, but without the pulses for the EU to integrate, the pump relay wouldn't switch on.
The damage is repairable, as long as you waterproof things with self amalgamating tape.

Yea true, very weak intermittent speak. Sometimes we would get literally no spark.

Yea we soldered and taped a new piece of wire in, slightly longer and rerouted it as to not touch the pulleys anymore