M42 Full Rebuild now won't start

[theTBLACK]

Yeah, hopefully. That big 22mm bolt is a real pain in the ass. If the woodruff key is missing, you can't use the starter to break it loose either because the crank would stop driving the chain sprocket once the nut comes loose and you'd have pistons hitting valves, so you will need a crank locking tool and a very large breaker bar in that case.

Good luck. Hopefully it is the pin or sensor.

So the pin just slides into that sprocket, and can go in any of those holes? No pun intended.

And is there a way to test if the crank position sensor is good or bad?

[bmwman91]

Yeah, hopefully. That big 22mm bolt is a real pain in the ass. If the woodruff key is missing, you can't use the starter to break it loose either because the crank would stop driving the chain sprocket once the nut comes loose and you'd have pistons hitting valves, so you will need a crank locking tool and a very large breaker bar in that case.

Good luck. Hopefully it is the pin or sensor.

[theTBLACK]

As far as I can recall, there is only one spot in the hub/flange that it can go.

Well, fingers crossed that it's missing, or that the crank position sensor is misaligned.

[bmwman91]

As far as I can recall, there is only one spot in the hub/flange that it can go.

[theTBLACK]

Okay, quick question for you.

How do I make sure that part 7 is oriented correctly?

[theTBLACK]

Yeah, sorry about the long post. A comfy couch plus a beer sometimes leads to a longer-than-expected post lol.

Anyway, yeah, if it is not that then I have no idea what it could be. This is already one of the most lengthy "M42 no start" sagas that I have ever seen!

It is insane man. I appreciate your patience and help. If this doesn't fix it, i'm giving up and throwing in an S52.

[bmwman91]

Yeah, sorry about the long post. A comfy couch plus a beer sometimes leads to a longer-than-expected post lol.

Anyway, yeah, if it is not that then I have no idea what it could be. This is already one of the most lengthy "M42 no start" sagas that I have ever seen!

[theTBLACK]

Yeah, I mean the last diagram in the post I linked a few posts up. The crank damper wheel is the big toothed thing that sits behind the big pulley that drives all of the belts. The crank position sensor is mounted in a little bracket at the bottom passenger side of the engine, sort of under the AC compressor. It points straight at the damper wheel and should be like 1-2mm away from the tips of the teeth.

http://www.r3vlimited.com/gallery/files/7/5/2/5/img_0401.jpg

You can see it in the linked image. The damper wheel teeth are visible behind the pulley at the bottom of the "triangle" formed by the belt. The position sensor is the little silver cylinder pointing at it in the very bottom middle. One of the teeth in the wheel has a small notch in it that should align with the arrow in the oil filter housing. You will also notice a 2 tooth gap where teeth are missing. You may need to remove the cooling fan to see all of this clearly.

If the crank position sensor is too far from the wheel's teeth or the wheel got installed in the wrong orientation somehow (which might indicate that a couple of other odds and ends are missing) then you would get a condition where you either have no spark, or the spark is timed totally wrong and isn't igniting any air-fuel mixture.

Here's a diagram of the parts related to the damper wheel's orientation.
http://www.realoem.com/bmw/enUS/show...diagId=11_4319

Part 8 slides onto the nose of the crank, and part 9 (the little woodruff key) holds it in alignment. However, part 8 slides past the key so that a bit of it sticks out still, so the key also aligns part 6. Part 6 has the pin, part 7, in it and that is what part 1, the damper wheel, aligns to. Sorry if that is a bit drawn-out. Anyway, it is possible to forget part 9, which ultimately means that the damper wheel is not aligned with the crank properly (the gap at the missing teeth is more or less what tells the ECU where TDC is), and the ECU will have bogus ignition timing. The crank damper wheel is the single most important element in the ECU's list of inputs because crank position and RPM are measured from it.

Missing the key is not all that big of a deal, mechanically, because it only aligns things during assembly. The big 22mm bolt (part 4) in the nose of the crank is torqued to 240 ft-lbs, and that squeezes parts 5, 6 & 8 against the crank with sufficient force that they do not slip (and it would be VERY bad of they did because the cams and crank would get out of whack and send valves into pistons).

A) If the woodruff key is missing, then you have to do some shitty work to make this right. You either have to open up the timing case, take the chain off and replace the key. You could alternatively try loosening the big bolt and rotating the damper wheel into the right position by visually aligning the teeth to match my diagram without opening things up. Either way, the big ugly bolt with 240 ft-lbs on it has to get loosened and re-tightened, and the tightening process would probably get things out of sync.

B) If it is just the little pin (part 7) that is missing, you just have to undo the 6 13mm bolts that hold the damper wheel to part 6 and align things without taking the timing covers off or anything. That's a fairly easy 1 hour job if you have a replacement pin or metal rod of the right diameter.



Who reassembled this engine, BTW?

Okay that was intense haha. I'll probably have to dive into that this weekend and see what is going on.

The mechanic who had the car last reassembled it - he may have missed something. Sucks for me.

I'm thinking that this has to be the issue, as we have discovered previously - everything else seems to be working just fine.

[bmwman91]

Yeah, I mean the last diagram in the post I linked a few posts up. The crank damper wheel is the big toothed thing that sits behind the big pulley that drives all of the belts. The crank position sensor is mounted in a little bracket at the bottom passenger side of the engine, sort of under the AC compressor. It points straight at the damper wheel and should be like 1-2mm away from the tips of the teeth.

http://www.r3vlimited.com/gallery/files/7/5/2/5/img_0401.jpg

You can see it in the linked image. The damper wheel teeth are visible behind the pulley at the bottom of the "triangle" formed by the belt. The position sensor is the little silver cylinder pointing at it in the very bottom middle. One of the teeth in the wheel has a small notch in it that should align with the arrow in the oil filter housing. You will also notice a 2 tooth gap where teeth are missing. You may need to remove the cooling fan to see all of this clearly.

If the crank position sensor is too far from the wheel's teeth or the wheel got installed in the wrong orientation somehow (which might indicate that a couple of other odds and ends are missing) then you would get a condition where you either have no spark, or the spark is timed totally wrong and isn't igniting any air-fuel mixture.

Here's a diagram of the parts related to the damper wheel's orientation.
http://www.realoem.com/bmw/enUS/show...diagId=11_4319

Part 8 slides onto the nose of the crank, and part 9 (the little woodruff key) holds it in alignment. However, part 8 slides past the key so that a bit of it sticks out still, so the key also aligns part 6. Part 6 has the pin, part 7, in it and that is what part 1, the damper wheel, aligns to. Sorry if that is a bit drawn-out. Anyway, it is possible to forget part 9, which ultimately means that the damper wheel is not aligned with the crank properly (the gap at the missing teeth is more or less what tells the ECU where TDC is), and the ECU will have bogus ignition timing. The crank damper wheel is the single most important element in the ECU's list of inputs because crank position and RPM are measured from it.

Missing the key is not all that big of a deal, mechanically, because it only aligns things during assembly. The big 22mm bolt (part 4) in the nose of the crank is torqued to 240 ft-lbs, and that squeezes parts 5, 6 & 8 against the crank with sufficient force that they do not slip (and it would be VERY bad of they did because the cams and crank would get out of whack and send valves into pistons).

A) If the woodruff key is missing, then you have to do some shitty work to make this right. You either have to open up the timing case, take the chain off and replace the key. You could alternatively try loosening the big bolt and rotating the damper wheel into the right position by visually aligning the teeth to match my diagram without opening things up. Either way, the big ugly bolt with 240 ft-lbs on it has to get loosened and re-tightened, and the tightening process would probably get things out of sync.

B) If it is just the little pin (part 7) that is missing, you just have to undo the 6 13mm bolts that hold the damper wheel to part 6 and align things without taking the timing covers off or anything. That's a fairly easy 1 hour job if you have a replacement pin or metal rod of the right diameter.



Who reassembled this engine, BTW?

[theTBLACK]

Every once in a while it will stumble on the first crank for one turn. Hardly any signs of combustion. It usually is just the exact same noise no matter what.

[theTBLACK]

Ok, so timing is good, you have spark and you have fuel. Do you get any misfires, stumbles or other signs of combustion?

Check the orientation of the crank damper wheel. At TDC the notched tooth and two missing teeth should be positioned as shown in the diagram I drew in the link. If that is off then the spark will occur at the wrong time.

Where is the crank damper wheel? And are you talking about the last diagram in the first post?

[bmwman91]

Ok, so timing is good, you have spark and you have fuel. Do you get any misfires, stumbles or other signs of combustion?

Check the orientation of the crank damper wheel. At TDC the notched tooth and two missing teeth should be positioned as shown in the diagram I drew in the link. If that is off then the spark will occur at the wrong time.

[theTBLACK]

With the cam lobes pointing "up and in" at TDC, cylinder 1 should be at the top and 2 should be at the bottom.

The cam sensor signal is not required for the engine to run. However, the crank sensor is 100000% mandatory and the car will not run without it. If you are getting spark though, then the crank sensor is probably fine because the ECU won't know when to fire the plugs without knowing the crank position.

So, upon investigation -

With cam lobes up and in at TDC, cylinder 1 is indeed at the top and 2 at the bottom.

It appears that timing is spot on - unless there is something else I'm missing :(

[theTBLACK]

With the cam lobes pointing "up and in" at TDC, cylinder 1 should be at the top and 2 should be at the bottom.

The cam sensor signal is not required for the engine to run. However, the crank sensor is 100000% mandatory and the car will not run without it. If you are getting spark though, then the crank sensor is probably fine because the ECU won't know when to fire the plugs without knowing the crank position.

Okay perfect. That is super helpful to know.

So next step would be to remove the plugs, and see where the cylinders are at in 1 & 2. I'll do that tomorrow and report back.

[bmwman91]

With the cam lobes pointing "up and in" at TDC, cylinder 1 should be at the top and 2 should be at the bottom.

The cam sensor signal is not required for the engine to run. However, the crank sensor is 100000% mandatory and the car will not run without it. If you are getting spark though, then the crank sensor is probably fine because the ECU won't know when to fire the plugs without knowing the crank position.