1986 325e Crank, no spark

[Sovereign]

Hey guys, First post on here, so I apologize if this is the wrong board for this but I was looking for some advice on furthering my troubleshooting on my 1986 325e

So, Crank and no start, so I started off with checking for spark. No dice, which progressed to further troubleshooting. This led me to convince myself the sound I was hearing wasn't the fuel pump and replacing both the TDC sensor and CPS. Firing the old parts cannon at her.

After that didn't work, I decided to order the Bently manual, and get myself a digital copy of the ETM. So where I am now, is I have 12v to terminal 15 on the coil, but from the sketchy reaching over the windshield test I performed, It does not appear to be receiving a pulsing ground signal on terminal 1. My current understanding of how this ignition system works is that the ground pulse signal is sent via the DME.

This leads me to believe that the DME may be at fault, but I wanted to seek some advice on it before ordering, or cracking open the DME and trying to see if any of the solder joints are obviously cracked, or in need of re-flowing.

Are there any more tests I can run to help me narrow this down to a DME specific issue, or anyway I can measure from the DME harness to ensure the CPS is sending a signal to the DME? The only other thing I think I need to check is the actual reference pin on the flywheel.

Timewise, would I be better off converting over to a 1.3 Motronic DME, since I want to eventually chip the car down the road, as opposed to attempting a repair on the DME / sourcing a new one?

Thank you!

[tomstin]

My first question: What did you do prior to this can not starting? Had it been sitting for a long time? Did you buy it dead?

When you replaced the two bell housing sensors, did you replace them one at a time? Easy enough to reverse them. Without both of those sensors working correctly the DME won't power the coil.

With the wiring diagram, did you check continuity from the coil to the DME connector? How about the bell housing cabling?

Switching to Motroinc 1.3 is more than replacing the DME. I would get this right before adding more confusion.

[Rustyeta]

You don't mention whether you tested the coil, that's definitely worth doing before you go replacing your DME. You should be able to check resistance there, won't tell you for sure that it's good, but if it fails that test it's bad.
I know my cheapo volt meter won't show a quick pulse, too slow to respond, so possibly the case with yours.

[Sovereign]

To answer the first question you had tom, I did in fact buy it dead. I also did the bell housing sensors one at a time, but I will double-check my work! I do need to check for continuity from the coil to the DME connector, as well as the bell housing cable.


And I do believe I had tested the coil at the very start of my troubleshooting, but I do have a much nicer multimeter now, so Ill double check that as well!

Thank you again!

[uturn]

Flood car? Did the PO tell you the car ran when parked? If so, undo everything, spray starter fluid in the intake while you crank it over. Solid state electronics, yea!