Engine turns over but won't start

[chefmike70]

1987 325
Two nights ago I drove car to a scout meeting. An hour later got in and it cranked and cranked but would not start. No sign of spark. Got a ride home and left it for the next morning. Got in and it started right up so I drove it home. Drove it a couple of times on short jaunts around town with no problems. Now it will not start. It cranks and barks once like it is about to grab and then nothing. If I let it sit for 10 minutes or so it will do the same. I have checked all fuses, the fuel pump runs after you turn the key to start and then let off. I have been searching threads and can't seem to find one with these symptoms. Any idea's?
Thanks

[dsphil]

Same problem I have before. I changed the main relay and CPS sensors and along with many other things. no problem since. good luck.

[chefmike70]

Since last post:
Went out to work on the car and it started and ran without doing anything to it. Drove around the neighborhood, turned it off and restarted it several times with no issues. Drove the kids to school and it died in the parking lot.
Had it towed to local mechanic. They kept the car for two days. It started and ran fine for them. They couldn't get it to fail.
I went and picked it up and as soon as I got home it died. Hasn't started since.
I replace the main relay, removed and cleaned the position sensors and reinstalled them and it Started!!! Then it died again and hasn't run since!
Once again it turns over, barks like it going to start then just turns over. Repeat after about 10 minutes.

[chefmike70]

Update

Since this original post I did a myriad of tests and checks that I read on this forum. Finally found an import specialists in Tyler that found the problem. He traced to the Motronic ECM and replaced it. Car great now, except for a persistent hesitation when shifting from 2nd to 3rd that has been there since I got the car.
Here is everything I tested/replaced:
Fuses
Main and Fuel relay
both CPS sensors
Idle Mixture Valve
All vacuum hoses
Fuel Pressure Regulator
ECM

Thanks to Johann Krueger at Import Auto Repair in Tyler TX

[Andy.B]

The po of my 325 (my brother) had pretty much the same story. Replaced just abut everything but it kept randomly dieing. He ended up parking the car for 6 years because of it! I put a used ecu in and haven't hat a problem since. Took the old one apart and there was visible corrosion on some of the traces and solder points. Internal corrosion on the ecu can cause some difficult to diagnose issues.