CRANK NO START 1986 325e

[tigerblood]

Whats up r3v so I have a crank no start and have done some diagnosis but am kind of stuck as to where I should go from here. I have an 1986 325e and it cranks but does not start. I have power to the coil, but I have no spark. also checked for fuel I have fuel going to the rail. I have replaced the ignition coil and cap and rotor and nothing has changed. After playing the old darts game I started to dig a bit deeper reading about grounds and other issues with this. I found the engine ground and used a jumper cable to give it a known good ground and this did not change the issue so the ground must be fine. Next I read about crank sensors going bad so I pulled them out tested them and the readings I got in resistance seemed to be in spec(around 90 ohms) as to what I have read. I also rotated the engine checking for a magnet. I only found one magnet so one of my questions is, is there only one magnet on the pressure plate? the flywheel teeth are all there and nothing looks damaged in there. My thought is if it was the crank sensors that went bad though wouldn't the engine start and just as the sensors get hot they would then cut out? Any help or input works, thanks guys

[101]

Got Bentley?

If you have power to the coil but no spark, the ECU is not grounding the coil to fire it.

The flywheel indeed has only the one magnet. Good that you checked that it was present.

The reference sensors resistance spec is 960 ohms +/- 90 ohms. Yes, they can flake out with temperature changes, but I'd start the diagnosis elsewhere ...

Section 6, page 48 of the Bentley manual has the ECU pin test that only requires a volt/ohm meter and a jumper wire. That way you check not only the various sensors but the wiring from them to the ECU. Also test the wiring for the idle control unit on page 46. Start there and tell us if all of those tests pass.

I once was in your shoes on an 87 eta no start. After chasing it for months it turned out to be a bad ECU. If you follow the Bentley manual checks carefully, you'll save yourself a lot of guess work.

[camip]

I had the same problem it was a bad ecu as well. Find someone local and borrow theirs to test it.

[hot carl]

did you check fuel pressure? or just that fuel was in the rail? i'd check pressure.
i had a similar problem on my 85 eta, turned out to be combo of bad fuel pump relay and bad ignition switch.
try jumping the relay with a short piece of wire. i forget the terminal #s but jump from the pin closest to the fender to the one furthest from it. not the ones front to back of the car. the relay is in the middle of the group of three on the inner fender by the airbox. with the jumper the pump will be on whenever the key is on, should give you good pressure. try to start the car, if it starts, you found your problem.
i forget exactly how we tested the ignition switch, but look around, i'm sure theres writeups.
good luck!

edit; just reread your post, check ignition switch

[tigerblood]

update;

hey guys so I found pinout and test guide for the ecu. All my power and grounds are good, also double checked the reference sensor and engine speed sensor at the ecu and got the same ohm readings, with that being said im leaning towards the ecu but still not ruling out the crank(reference sensor). I found someone local with an ecu so am gonna try that and go from there thanks for the help and will keep you guys updated

[tigerblood]

Update: Fixed

thanks again for the help guys, got an ecu last night off a guy in west philly swapped it in this morning and the beast fired right up! I guess about 300,000 miles is the life of an ecu thanks again!