Ran great for 6+ months, now it won't start

[JGood]

One thing I've never seen posted is what to actually check for as far as power/ground at the c101.

For instance, pin 1 of the c101 is alternator power. So while cranking should I have 12v across pin 1 of the c101? Pin 7 is power for fuel pumps, so should I also have 12v there?

What about pin 10, the ignition? Is that a ground circuit like some other cars? So I should check to see if that becomes a good ground during cranking?


What I don't understand is, if I'm getting 12v at main/fuel relays, and it's cranking, what could possibly be wrong at the c101? The fuel pump, starter, and ignition should be all that's required to start, right?

[JGood]

It's not the c101. When I said everything ran perfectly for 6 months, I lied (just to simplify things). I've been having issues with the corroded c101 pins which need cleaned and wiggled around every few weeks. However, it is working fine at this time. I cleaned and wiggled for about an hour, haha. I am getting continuity through it. The issue is different as well, when the c101 gives me trouble, it's a no crank condition. Now it's cranking but not starting.

[jrdeamicis]

That C101 connector is a mofo. Clean that shit ASAP.

[z31maniac]

I'm not familiar enough with connectors, but I'll just throw this out there.

Are any of the pins/etc, corroded/cracked/messed up looking? You know everything was fine, and now you have dislodged something in one of the connectors?

Again, just pulling that out of my ass.

[JGood]

Oh, and the main relay and fuel pump relay get 12v with the ignition switched on.

[JGood]

94 m50 -> 85 325e, made my own c101 adapter (round x20 -> rectangle c101), everything worked perfectly for the past 6 months.

Was prepping the car for state inspection, just going over everything to make sure it's ready. Unplugged the c101 adapter to gain access to some things. Plugged it back in, now the car won't start. It cranks and cranks and cranks, but won't try to actually start.

I know it sounds like something just got unplugged and I forgot to plug it back in. But I just spent the past few hours rebuilding the entire fucking harness and checking continuity. Even the c104 wires. It's all fine.

The only thing that I found that seemed odd to me, was during my continuity check, on the body side c101, probably 6 or so of the 9 wires had continuity to each other. As in, almost all of the pins on the body side c101 are connected. I didn't mark down which ones. So I checked to see if they were power or ground, and they were all grounded. Is that normal?


Besides that, everything else is fine. I tried disconnecting the battery, the ECU, the relays, and plugging it all back in. Nothing.