M42 not starting
 

After a big coil failure resulting in a new DME around January it ran and drove fine. After a few weeks noticed it would start randomly cutting out - always in higher rev ranges - 4500-5500. Happened again a couple of weeks ago at low revs - stalled. Hard to restart, but got it going - went to work. Now not starting at all. I have power to the fuel pump - can hear it run. Put a plug tester on - looks like no spark, bench tested main relay - ok. I don't want to throw parts and just hope. Is there a test for the coil pack, maybe my new one is faulty - I have 12v to the coil, but no spark coming out. What else should I be looking at? Crank position sensor?...

These damn cars. I read somewhere something about the ews not letting the coils fire or something when it doesn't communicate. But you say its getting 12v so I dunno.. But if you are in the area u can use my spare coil pack for testing

Thanks - I think I'm down to a few things - bad coil, ews, maybe crank position sensor or a bad wire. The coil has a warranty, so I'll swap it out - thanks for the offer though. Problem started intermittent - so I don't really think ews, but a broken wire is a possibility...

Have you checked your fuel pressure? Did you replace the plug wires and plugs along with the coil when it failed? Have you even tried to scan for codes?

Did the pedal pump thing - no codes (it's a 95). Haven't checked fuel pressure. The no spark issue pretty much sent me a different direction. Wires were changed with new coil in January. Replacement coil is at the store, I'll know more a little later

Tested the crank position sensor - it was dead - now it runs, but on 3 cylinders. When the coil failed a few months ago, it shorted and fried the DME. Even after toasting the DME it ran - but on 3 cylinders... Now I'm thinking the dinan chip got damaged, but was limping along - then took a dump. Tested continuity of the wiring between the coil connector and DME plug pins. Wiring seems intact visually and with continuity. Next up is swapping in a stock chip after I figure out the EWS sync thing work around. Anything else I could be overlooking? Coil is fresh, new plugs and wires. Seems like the DME is not sending a signal for #1 to fire.

The chip it's self will never fry it's almost impossible to damage or destroy the embedded data without special hardware. I would look at sensors

what other sensors might cause a no-spark condition on 1 cylinder? cam position? o2?

I would think the coil would cause an issue like that.

I thought the same at first - brand new coil - thought I might have gotten a bad one, to be sure, replaced under warranty - same issue.

It's possible you have a bad coil driver in the DME it's self. I have heard of this happening.

I've swapped in a couple of different DMEs with the same result. I'm probably over thinking it. Seems the likely suspect is a cam position sensor. In seeing the damage to the DME from the original meltdown, it also wouldn't surprise me to have a damaged chip - so I guess those are the next 2 theories to test.

ok, not the cam position sensor, not the coil, not a wire fault, not the DME. Outside of the main chip, I'm starting to run out of options. Anyone have a spare red label dme or spare dinan/turner chip?

Just because the pump is running you can still have a failed pump.. My 95 the pump makes no noise at all... Hmm.. Have you attached a fuel pressure gauge?

Dave

finally sorted - woot - although I'll admit some of the problem was my own making. In the end, failed crankshaft position sensor, failed camshaft position sensor, previous bad coil and owner somehow crossed plug wires 1 & 2 somewhere in the routing. Runs perfectly today.