Author Topic: no power to coils (Read 3567 times)

mwilderl · « **on:** August 13, 2010, 12:09:57 AM »

Almost done with swapping an m42 into my e21, just there is no power to any of the coils. The fuel pump works and it turns over, but there's no spark. Any suggestion would be very appreciated.

If it means anything, there's no O2 sensor hooked up.

DesktopDave · « **Reply #1 on:** August 13, 2010, 07:06:02 AM »

I don't think that the DME controls current to the coils. IIRC, the DME grounds the coils to fire the plugs. Lemme dig out that trusty ETM or a wiring diagram and have a look-see later today.

Terminal 3 on all coils should be hot on start, terminals 2 are your (secondary?) ground, terminals 1 to the DME, right? The ETK notes that terminal 56 on the DME might require +12v off the coil circuit. Perhaps to sense if the coils are connected?

Not to be Mr. Obvious here, but you have the block well grounded too, right?

mwilderl · « **Reply #2 on:** August 13, 2010, 11:57:57 PM »

Have any idea where the power comes from?

The block is grounded well, it wasnt at first, but then the started didn't work either.

Thanks for the help, I'll be working on it all of tomorrow hopefully

DesktopDave · « **Reply #3 on:** August 14, 2010, 12:45:32 PM »

I'm almost positive that the coil power comes right off the positive junction block at the firewall, then through the C101 round connector plug (main engine harness) to the coil harness.

dvmotorsports · « **Reply #4 on:** August 14, 2010, 03:14:44 PM »

oh god, i should have answers to this, but my brain is still fried from the last to coil jobs

mwilderl · « **Reply #5 on:** August 14, 2010, 06:48:22 PM »

There is a possibility i missed the wire when i made the conversion harness from e21 to m42... any idea of what color the wire might be? Suppose ill start the guess and check method for now.