Author Topic: Non-Start electrics HELL (Read 4423 times)

Royalratch · « **on:** November 25, 2009, 03:28:56 PM »

1990 318iS M42.

I removed some redundant alarm / immobilizer wiring that had it's control unit cut out years ago - car always ran fine.

I went to start the car after a few months of restoration and my engine guys said it started and ran fine after they'd rebuilt it.

So I go to start it, it cranks for a second then I hear a loud pop from the engine bay and now nothing. Some diagnostics I've since done.

Is the battery okay - YES
Does ignition wire (black/yellow) from key have voltage - YES
Does ignition cutout loop (green/blue) have voltage - YES
Does Fuel Pump Relay and DME/ECU relay have voltage - YES
Are those relays okay - YES
Are all relevant fuses okay - YES
Does starter crank when voltage applied directly - YES
Is there spark - NO
Does fuel pump engage on ignition - NO

Basically there is no spark, no ignition and no fuel. The only thing I can think of that affects all these simultaneously is the ECU and I have fried it somehow. I will check the coils tomorrow for voltage and also try my spare ECU but after that I'm out of ideas...

DesktopDave · « **Reply #1 on:** November 25, 2009, 04:10:38 PM »

I'd figure you're right on the DME/ECU. If it shorted the injector or coil transistors it'd pop nicely.

I don't think the Euro cars ran a Check Engine Light (CEL)...did they? You can see the DME working if that light turns on at key position 2.

Royalratch · « **Reply #2 on:** November 26, 2009, 03:20:33 AM »

No DME type light on the dash. So why would it pop like that? And what's to stop it happening again with a new ECU?

Royalratch · « **Reply #3 on:** November 26, 2009, 08:30:57 AM »

An additional check - no voltage to the coils at any key position.

!

Ramblin MAn · « **Reply #4 on:** November 26, 2009, 09:45:23 AM »

Had the engine sat for any length of time? I had that same thing happen to me on my e21's m42 but the pop was the timing chain tensioner getting pressure. Scared the hell out of me. To top it off the engine wouldn't fire. Pulled the valve cover and checked to see if I jumped time but all was well. Gave the battery a good charge and it fired right up. The battery was just too low to run everything and crank the motor at the same time.

Royalratch · « **Reply #5 on:** November 26, 2009, 03:42:44 PM »

Battery is fine. Its hooked up to a battery charger/conditioner 24/7.

Royalratch · « **Reply #6 on:** November 27, 2009, 01:03:39 PM »

Desperate bump.

RED IS 91 · « **Reply #7 on:** November 27, 2009, 07:53:35 PM »

Did you switch out the ECU ?

Royalratch · « **Reply #8 on:** November 28, 2009, 12:25:07 PM »

Not yet - has been delayed in the post!

The starter motor now starts but the engine still does not catch - no reason, just like that!

Still no activity from the fuel pump at any key position.

lindol · « **Reply #9 on:** December 12, 2009, 07:24:01 AM »

Hi,
I went through a non-start problem some time ago that is documented on this site, see:
http://www.m42club.com/forums/showthread.php?t=8474
If you go to post #26 you will read that I made my own test light to get the fault codes, it worked a treat except for giving me the code that nothing was wrong!
Good luck,
David