M42 Full Rebuild now won't start

[theTBLACK]

Not always. If you are one tooth off it'll still run but then again if you are more than that you run the risk of hitting valves and pistons.

Check the easy stuff first and then report back. Im sure it is something stupid.

When you key on engine off before you crank is the CEL illuminated?

CEL is illuminated at this point.

[theTBLACK]

Unplugged the afm harness and crank it. See if that makes any difference in cranking.

I tried this - didn't make a difference.

[varg]

Verify that not only is valve timing correct (I read you have done that part), but that the sprockets are oriented correctly with relation to the cams.

[theTBLACK]

Verify that not only is valve timing correct (I read you have done that part), but that the sprockets are oriented correctly with relation to the cams.

The sprockets as in the two wheels with the surrounding chain at the front of the motor? How would I go about doing so, and how will I know they are in the right position?

[varg]

The sprockets as in the two wheels with the surrounding chain at the front of the motor? How would I go about doing so, and how will I know they are in the right position?

Yep. Verify that with the engine at TDC and the cams in their TDC position, the timing marks on the sprockets are in this pictured position and the trigger dowels are present, intact and at the ~7o'clock position.



If your fuel injectors are firing and your spark is strong, it's down to timing. Something isn't occurring when it should, we just have to find what and why. While you're at it, you may want to also verify the crank pulley's position with the old "long wooden dowel down the #1 spark plug hole" trick by checking that the timing mark on the pulley and timing case are aligned when the TDC position is indicated by the movement of the dowel. I'm not trying to imply that you don't know how to do this stuff, just putting out there what I've seen happen to others.

[theTBLACK]

Yep. Verify that with the engine at TDC and the cams in their TDC position, the timing marks on the sprockets are in this pictured position and the trigger dowels are present, intact and at the ~7o'clock position.



If your fuel injectors are firing and your spark is strong, it's down to timing. Something isn't occurring when it should, we just have to find what and why.

Mine looks exactly like that first photo. Tick marks straight up and down.

[bmwman91]

Are the cams AND crank in the TDC position together? The cam lobes for cylinder #1 (front-most one) should be pointing up and in when piston #1 is at the top. I am guessing that maybe piston #1 is at BDC when the cams are at TDC.

Check out the diagram in my other thread (last image in the first post). It spells things out very clearly. You want everything positioned shown to the left of the image for Cylinder 1 TDC for Power Stroke.

http://www.r3vlimited.com/board/showthread.php?t=374858

[theTBLACK]

Are the cams AND crank in the TDC position together? The cam lobes for cylinder #1 (front-most one) should be pointing up and in when piston #1 is at the top. I am guessing that maybe piston #1 is at BDC when the cams are at TDC.

Check out the diagram in my other thread (last image in the first post). It spells things out very clearly. You want everything positioned shown to the left of the image for Cylinder 1 TDC for Power Stroke.
http://www.r3vlimited.com/board/showthread.php?t=374858

The cams are in the same position as the diagram you referred to - Cylinder 1 TDC, and the tick mark on both sprockets are pointing straight up, like the photo posted previously.

Is there a way that the cam lobes and ticks are in the right place, but the piston at BDC?

[bmwman91]

The cams are in the same position as the diagram you referred to - Cylinder 1 TDC, and the tick mark on both sprockets are pointing straight up, like the photo posted previously.

Is there a way that the cam lobes and ticks are in the right place, but the piston at BDC?

Yeah, you could have gotten the crank 180 degrees off. IIRC the stock flywheel has 2 holes for the alignment dowel, so it is possible to mix things up that way. Pull spark plugs 1 & 2 with the engine at TDC and make sure that piston 1 is above 2.

[theTBLACK]

Yeah, you could have gotten the crank 180 degrees off. IIRC the stock flywheel has 2 holes for the alignment dowel, so it is possible to mix things up that way. Pull spark plugs 1 & 2 with the engine at TDC and make sure that piston 1 is above 2.

So should I just pull the plugs, and put a wooden dowel in 1 and 2 and make sure 2 is higher? (With tick marks and front lobes at TDC)

[theTBLACK]

And a side question - would a bad crank position sensor or cam position sensor cause a no start? Mine were replaced, but I'm not sure if they are faulty - or how to test/what signs would be apparent if they were working.

[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.

[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.

[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 :(

[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.