M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: Eric on August 07, 2016, 10:25:07 PM
-
I have a 91 325i with a m42 swapped in it. It has a cop conversion. This weekend I replaced the valve cover gasket. One of the studs would not make torque spec but it was only one and all the others torqued to spec. I waited a day before I tried to start it and it started to miss on #4 while I was warming it up in the garage. I held my and and ear by the suspect stud but didn't notice and vaccum , all of a sudden the #4 coil pack puked black goop out of the side and started to smoke like crazy. I thought it was just a bad coil pack so I found two extra at the local yard. I got home and tried swapping them around and managed to melt two more coil packs. I tried splicing in a different coil plug on number 4 and no change. I even tried swapping in a extra ecu and no change. The car has new plugs with the gasket change so I tried and old plug in #4 and still nothing. I know it's not firing because there is fuel on the plug. The coil is getting super hot so it has to be getting power right? I have no clue what to try next at this point please help!
-
Sounds like you have a short in the coil pack harness somewhere. I'd bet it's in the wiring harness near the coil packs. They tend to flex when plugs are changed. Pull the DME connector and test all coil wires. I'd do a continuity test, then a ground test, then look for 12v on all wires with the ignition on. You might have to manipulate the coil harness to cause the short.
Each coil plug has three terminals. According to the E30 ETM:
Pin 1 on each coil plug is the "floating" ground for each coil primary. Should be a black wire, although hard to tell since it's shielded co-ax cable. It's a grounding wire, but it doesn't ground to the chassis at all. It runs directly back to the DME instead. Coil #1 goes to DME pin 25, #2 to pin 52, #3 to pin 24, #4 to pin 51. If I recall correctly, the DME switches the coils on those floating ground wires...it has four big MOSFET driver transistors to handle high current for that purpose. The shielding jackets are grounded to chassis at the passenger shock tower.
Pin 2 on each coil plug is chassis ground, runs back to G103 on the passenger shock tower. It's shared with DME pin 26. Might be a brown/orange wire if an E30 donated the wiring harness.
Pin 3 on each coil plug is the positive wire for the coil primary. Should be green, and should see 12v in either start or run positions.
-
I seem to have fixed it by re soldering the power wire making sure to trim back the shield part of the wire to avoid shorting. I bought a multi meter to do continuity but re soldering seemed to fix it. Thanks for the pin out locations I was searching forever!! I'm still kind of scared of fire, should I try to run test still even though it's running fine?