Last week my 740 died on the freeway on my way to work. Long story short, it turns over but won't start. I tested the plugs and I'm not getting spark. Here's what I've tried...

- new distributor cap and rotor.... didn't work
- new ignition coil.... didn't work
- ICM.... didn't work
- ECU.... didn't work

After all that, car still turns over but I'm not getting any spark. What could I be missing!?

Any help would be appreciated!

Thanks.

 

Check to see if your timing belt broke. Open the oil cap on the top of the engine and shine a flashlight in there while a buddy cranks the engine. If the cam shaft doesn't turn then your timing belt is broken.

If the timing belt is ok, then more than likely the issue is the hall sensor on the distributer. It provides the pulses to the ECU/ICU which drives the spark.

'86 is also in the middle of the biodegradable wiring harness years which means it could be a wiring harness issue unless the harness has been replaced.

 

Thank you! It was the hall sensor. Grabbed a used distributor from the junk yard and swapped it out. Started right up. It's been running for about a week and now the issue is coming back! It just stopped running while I was driving, had to coast to the shoulder. Waited about 10 minutes then it started right up again. I'm at a loss. Any more ideas? Thanks!

 

I'm not as familiar with that version of the ignition system as my cars are post '89 which has a different ignition system. If it is still failing when warm, it could be the power stage (if your car has one). I don't know where it is located for a 740 but you could always look it up here: https://www.brickboard.com/FAQ/700-900/. I have never had one fail on me but I have read others that have.

Also, like I said in my first post, your car has the biodegradable wiring harness which can cause all sorts of electrical gremlins. Impossible to diagnose those over the internet