M42 Full Rebuild now won't start

[theTBLACK]

So as a recap for anyone that views this and for myself, here is where we are at.

1. Fuel pressure is good. New pump, new filter, injectors are not clogged, and the spark plugs are getting wet.

2. We have spark. Taking out each plug and grounding it results in a spark when the engine is cranked.

3. DME is good - I have two working DME's.

4. AFM has been replaced.

5. Crank position sensor, and Cam position sensor both have been replaced (CKS is questionable).

6. Timing appear to be spot on. Both lobes at cylinder 1 point up and in at TDC, marks all line up, arrows straight up, cylinder 1 piston is at the top, cylinder 2 piston is at the bottom. I even checked the part numbers on the intake and exhaust cams to make sure they were the correct cams.

7. Compression is good among all cylinders.


GAHHHHH.

[bmwman91]

Is it somehow possible that you mixed up the plugs for the crank and cam position sensors where they plug into the black electrical box under the intake manifold?

At this point I have NO idea what's up here. The timing looks great. 1000 Ohms is a tad low, so maybe you can try swapping in a known working crank sensor.

Have you done a compression test?

[theTBLACK]

Is it somehow possible that you mixed up the plugs for the crank and cam position sensors where they plug into the black electrical box under the intake manifold?

At this point I have NO idea what's up here. The timing looks great. 1000 Ohms is a tad low, so maybe you can try swapping in a known working crank sensor.

Have you done a compression test?

I'll try and switch them and see if that makes a difference. Do you know which one goes on top and which goes on bottom?

And I'll try grabbing a known working crank sensor.

Yes, compression was strong across all cylinders.

[bmwman91]

Cam sensor pugs in on top.

[theTBLACK]

Okay. I'll try that first thing tomorrow. This is so mind blowingly difficult I can't believe it.

[bmwman91]

Seriously. I am willing to bet that it is some dumb little thing that we are all overlooking.

Did you verify that you connected the right coil pack to the right connector from the ECU? I assume that you still have stock ignition with the coils over on the fender? Or were the coils never unplugged from the ECU?

All 4 spark plugs are wet with fuel after cranking?

If the timing is good, you have fuel and you have spark, then it seems like it has to be a case of the spark being delivered to the wrong cylinder at the wrong time. I mean, if there is fuel in there and a spark, you would at least get some stumbling or backfiring or something. How did you verify that the ignition coils were firing?

Are you using NGK BKR6EK spark plugs? Really, any spark plug should give you SOMETHING, unless you put in some sort of really strange ones. This one's a long shot.

When you removed the engine for the rebuild, did you take the wiring harness out with it?

Do you hear the fuel pump prime when you turn the key to Run (1 click past Accessory)? Does it run while cranking?

Check your fuses too.

[theTBLACK]

Seriously. I am willing to bet that it is some dumb little thing that we are all overlooking.

Did you verify that you connected the right coil pack to the right connector from the ECU? I assume that you still have stock ignition with the coils over on the fender? Or were the coils never unplugged from the ECU?

All 4 spark plugs are wet with fuel after cranking?

If the timing is good, you have fuel and you have spark, then it seems like it has to be a case of the spark being delivered to the wrong cylinder at the wrong time. I mean, if there is fuel in there and a spark, you would at least get some stumbling or backfiring or something. How did you verify that the ignition coils were firing?

Are you using NGK BKR6EK spark plugs? Really, any spark plug should give you SOMETHING, unless you put in some sort of really strange ones. This one's a long shot.

When you removed the engine for the rebuild, did you take the wiring harness out with it?

Do you hear the fuel pump prime when you turn the key to Run (1 click past Accessory)? Does it run while cranking?

Check your fuses too.

The coils were replaced - maybe I should try the original coils.

All 4 spark plugs are wet with fuel after cranking.

I pulled out each spark plug and grounded them on the strut tower - they were all sparking.

And yes, those are the exact spark plugs that i'm using.

The fuel pump relay was bad so I jumped it - it was definitely on while we were cranking as I could hear it. Still waiting on the replacement to show up.

[bmwman91]

When you replaced the coils, is there any chance that you reconnected them incorrectly? I'd imagine that you have quadruple-checked the wires from the coils to the plugs, but what about the plugs from the ECU to the coils? At this point it seems like it MUST be a "spark at the wrong time" issue since you'd get stumbling and misfires at the very least with fuel and spark occurring.

Is it possible that water got into the gas or something?

[theTBLACK]

When you replaced the coils, is there any chance that you reconnected them incorrectly? I'd imagine that you have quadruple-checked the wires from the coils to the plugs, but what about the plugs from the ECU to the coils? At this point it seems like it MUST be a "spark at the wrong time" issue since you'd get stumbling and misfires at the very least with fuel and spark occurring.

Is it possible that water got into the gas or something?

I wasn't the one who reconnected the coils, so I will make sure they are all in there and working correctly. I will also try the old, known working coils as the motor was running before the rebuild.

Not only did I quadruple check the wires from the coils to the plugs, I replaced them all together with new bosch wires. As long as cylinder 1 is the one closest to the radiator going back, then they should be in the right order.

Is there a specified order for the coilpacks or are they universal? I'll triple check that they are all connected, and quadruple check for spark on each spark plug.

No water got into the gas - it has a half tank of premium right now and a new filter/pump and everything.

I just ordered a new fuel pump relay so i'll get that in this weekend - i'll also be double checking the CPS and CKS into the box under the intake to make sure they are plugged into the correct places - as that definitely could be an issue.

I will keep you posted, and I owe you for all of your help!

[bmwman91]

All 4 coils are the same part number. However, since they are independent, they need to be connected to the proper plug from the ECU because the ECU tries to fire each cylinder at a specific time. It would be pretty hard to goof that up since the wire harness gets sort of stiff and the plugs should more or less stay near their respective coil.

As far as verifying that the ECU is properly connected to each coil, the only way that I can think of to check this is to unplug the ECU and use a multimeter between the pins in the big 88 pin plug and the respective pins in the coil connectors. See page 32 of this:

http://www.armchair.mb.ca/~dave/BMW/e30/e30_92.pdf

Make sure that ECU connector pin 25 has continuity with pin 1 on the connector for coil 1, and so-on for the other coils. Really, I can only think that somehow coils 1 & 2 and 3 & 4 got jumbled up at this point.

[theTBLACK]

All 4 coils are the same part number. However, since they are independent, they need to be connected to the proper plug from the ECU because the ECU tries to fire each cylinder at a specific time. It would be pretty hard to goof that up since the wire harness gets sort of stiff and the plugs should more or less stay near their respective coil.

As far as verifying that the ECU is properly connected to each coil, the only way that I can think of to check this is to unplug the ECU and use a multimeter between the pins in the big 88 pin plug and the respective pins in the coil connectors. See page 32 of this:

http://www.armchair.mb.ca/~dave/BMW/e30/e30_92.pdf

Make sure that ECU connector pin 25 has continuity with pin 1 on the connector for coil 1, and so-on for the other coils. Really, I can only think that somehow coils 1 & 2 and 3 & 4 got jumbled up at this point.

Okay a few updates -

1. CPS and CKS were definitely on backwards.

I switched those, went to crank it, and it finally stumbled a little bit. It was trying. But it never fired, I don't know if I flooded it or what because now it just cranks and cranks.

Is there a diagram that shows how the wires from the ECU come into the coil pack?

[theTBLACK]

I'll check for continuity on those as well tonight.

[Dj Buttchug]

damn this is still going. At least its firing now. OP like the other said check the coil plugs where the engine harness actually plugs into the coil.

[theTBLACK]

damn this is still going. At least its firing now. OP like the other said check the coil plugs where the engine harness actually plugs into the coil.

Yeah man. Stay tuned!

That's next - I will check all of them. I'll be checking that first thing Saturday morning.

Also, I'm waiting on a fuel pump relay - right now I'm jumping it and it's on all the time - might be getting too much fuel and flooding. Should be here Saturday.

[Ronan]

I swapped it, still the same problem.

Make sure the fuel supply line and return lines are correct. I swapped those on my m42 rebuild. Wouldn't start. Swapped them back and it cranked right up.

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