E36 M3 cranking no start RESOLUTION

[Spartanwarrior]

hello all, its been a while since i've been back on the forums and why else but because something went south. my m3 has been sitting for some time and found its way to the back of my to-do list, but low and behold i finally found time for my old friend. its a 1995 m3 5-speed with the 413 DME and for the longest time i had a cranking no start issue. it first started out as a hiccup when going over bumps or imperfections on the road. it almost felt like the ignition would cut out then turn back on, it was very linear and not like running out of gas. after the hiccups became a regular occurrence (happening more than once per drive cycle) it finally called quits. at this point i had no spark and no fuel and worst of all no communication with scan tools. i tried replacing crank and cam sensors but no change, swapped DME with a known good one and verified my current one was working in a second 95 m3 no change, bench tested all relays no change, checked and replaced all fuses no change (fog lights work now). power was present at all ignition coils indicating my ecu "on" relay was working just no signal. i was convinced my ews was killing the system, so i opened up the DME bus connector and snipped pin #66 (solid green wire) no change. still have no communication to scan tools, and noticed no check engine light indicating my DME was not communicating with the ips. i hooked up a vantage and scoped the can lines for activity with key on, still nothing. unhooked ALL modules with can communication one at a time to see if any were dragging down com, to no avail. at this time also verified can lines were not shorted to power or ground. checked for power and ground at the DME, ground was present and so was power, but not on all power wires. used a multi-meter and checked for power at all engine management related relays. power was present but noticed there was no clicking on any relays when cycling ignition on and off. strange, they all are good. happened to find a google image of a few relays under the steering column. removed and bench tested, all good still no change. just to humor myself i took all relays and scuffed up each pin with some 200 grit sand paper, then re-installed. check engine light came on, cycled key to start. BOOM the sound of collapsed lifters clicking away! frustrated and happy at the same time i re-assembled the interior and test drove. like it was all a bad dream. moral of the story, check the basics!!!! summary below

SYMPTOMS:
- cranking no start
- no spark
- no fuel
- no CAN com or CEL

REPAIR ATTEMPTS
- CKP & CMP sensors
- EWS delete
- swapped DMEs (had a spare 413)
- replaced bad fuses

FINAL RESOLUTION
- resurfacing relay pins, i'm fairly certain the suspect relay was the one tucked up to the left of the steering column as i was removing and re-installing all relays in the engine bay fuse block and nothing changed until i cleaned the one under the column. the relay i'm suspecting is the one circled with arrows around it in the picture. disregard the other writing as i borrowed the image from google, too dark to get a good picture of mine.
bmw relay.jpg
keep in mind i did resurface the pins on ALL the relays, im not certain which one did the trick and frankly i don't really care so long as it fixed the issue. it makes sense considering how old the car is, carbon builds up over time causing too much resistance and possible enough to turn a relay off. if any of you know what relay the one under the dash is feel free to reply so that others may have some sort of reference. just felt like sharing my experience as i know exactly how frustrating this issue is especially with how much information is readily available. i hope this can be of use to you and if nothing else its worth a shot, and cn be something to check off as a possible cause. i wish you luck with your project, be safe and have fun!

[blckstrm]

This is great advice. I've had to do the same with my brake light switch twice (both times ordered a new switch with the wrong number of pins), and did it with the seat switches in my Escalade, too.

Solid solution, and more important, the advice - check the easy things first.

[tripitz]

This is great info. I'm dealing with the exact same issues right now after an engine swap and OBD1 conversion. I've got a few other culprits like a possibly corroded terminal in the engine bay that I'm going to clean up. It may be a lot of little things adding up to my DME not working... Thanks for the advice. Will take a look at this.