M42 (swap into 2002) Tries, but just won't start

[pklym]

Thanks, Gerta. We think the crank is solid.

Last night we did some more diagnostics. Nothing too revealing.

We had some makeshift noid lights on the injector harnesses and some inline spark tester lights between the coil and plugs. With the intake manifolds off but the crank and cam sensors, plus temp sensor, plugged in, we cranked and observed the lights using slow-mo video. Both injectors and coils fired in wasted spark mode (1+4, 2+3 on the coils, all four injectors at once). It would continue in this mode and never switch to firing order for either. We swapped cam sensors (new sensor replaced by new sensor) and crank sensors (same), and plugged in and out the o2 sensor, we also swapped ecus. We did those one at a time. With no combination did we get to firing order. Which is odd, because the night before the coils would go to firing order.

The firing would not always remain consistent, sometimes there would be gaps between either the coils or injectors firing. Other times they would just stop firing completely.

Though the relays and wiring have all checked out good, we will be replacing the main relay next.

We also verified timing is still spot on, the crank dampener is lined up properly, the cam and crank sensors are not swapped and go to the proper ecu pins, every sensor ohms out correctly.

Right now we are confused why the coils and injectors won't get to their firing order after a few cranks, previously, the coils would but the injectors would not. Does the engine need to actually catch or start running for that to happen? I thought it was just a few cranks so the sensors could send a reading to the ECU?

Do any other sensors need to be plugged in to get the engine out of wasted spark mode?

Hopefully the main relay (which would get hot to the touch) is overheating and causing inconsistent power. The coils and injectors all seem to fire when told to and do not appear to be the problem. Compression is 185 across the board. Spark + Fuel + Compression = :( :( :(

[bflan2001]

Sorry if this has been covered already but before you spend more money I would try rearranging the plug wires, even if you're sure they're right. It really sounds like your ignition is firing out of order.

[pklym]

When it goes into firing order, it fires correctly, 1-3-4-2, from radiator to firewall. Also, the coils match to the pins on the ECU correctly, 1-2-3-4 (radiator to firewall) so the order does not seem to be the issue. Thanks though, it really feels like that should be the problem.

[bflan2001]

I believe the metal body of the ECU needs to be grounded, could that be your issue? Just throwing out things that caused issues on my swap, apologies if you've covered this stuff already. I know the frustration you're feeling right now, hang in there, you're so close!

[pklym]

We've tried grounding the ECU with jumper cables and that has not helped at all. Just replaced the main relay and fuel pump relay, with each replaced part it seems to WANT to start more but still won't. Right now spark plugs 1 & 4 seem to be richer than 2 & 3. I just ordered some brand new coils as we continue to throw parts at this thing.

I am in search of a KNOWN GOOD ECU to borrow if anyone has one lying around. The ECU I got with the engine was supposedly good, as was one I purchased on ebay, but I would love to get a hold of one that someone who is not trying to sell to me can assure is good. I would pay for shipping and could pay a security deposit if necessary. The car is in Kennewick, WA and I am in Portland, OR so could pick up in either location or pay for shipping. Please let me know if any of you have one lying around, or perhaps in a car that is out of commission for a project of some kind.

[pklym]

Updating for posterity:

Great but frustrating news!!

The car is alive. It runs. The problem appears to be fixed.
I had been coming across an old, apparently discontinued, part number for the crankshaft position sensor. It is NLA. But I found one on ebay, bought it, and now the car runs. This has been almost six months chasing this no-start and throwing two new, supposedly correct, crank sensors at it. So incredibly frustrating, but thank goodness its alive.

The part number that works on my engine, with a 91 318i ecu, is 12141721968
The one that didn't work was 12141721504

[roguetoaster]

Good the hear!

If you still have both sensors could you check out resistance numbers across the pins on each and post them here?

[pklym]

Good the hear!

If you still have both sensors could you check out resistance numbers across the pins on each and post them here?

I'll try to test them again, but each one ohmed within spec.

The angle the wiring comes off the sensor is different between the two part numbers, one goes towards the belts and the other heads straight up the engine

[roguetoaster]

Ah, that's good enough then.

[pklym]

Just realized as I prep my Bosch CPS for return to FCP Euro that they sent Bosch p/n 0261210047 as an interchange part for the order of p/n 12141721504. So I guess I am updating this to say I do not know if 12141721504 would not work on this car, but instead that 0261210047 does not work. Be careful ordering this part from FCP Euro. I have explained my issue to them and hope they refund my money and verify their compatibility.

[downforce22]

0261210047 does not come up on realoem, so it must not be from a bmw. Thats a frustrating problem but great that you found the fix.

Vids of m42 02??

[CFeld]

I had the same issue, mine was timing related.