Still having spark issues on freshened motor

[krazykraut]

I pulled the engine from my '87 325i replaced the 220 head with an 885 head along with bottom end rebuild.... I currently have a 525 ecu, do i need to run a 153 ecu with an 885 headed M20b25?

But a different/wrong ecu would not be the problem, it would just run funny correct?

I currently have no spark, and no power from the engine harness' leads to the coil, so I want to know which ecu I truly need....so that as i get another one to eliminate the ecu as the problem, I get the correct one.

Any other ideas as to why I do not have power (voltage) to the coil as the car is being turned over would be great?!

[jlevie]

Power to the coil + is furnished by the ignition switch via C101. A splice in the harness feeds the START signal to the DME from the wire that feeds the coil. If you don't have power to the coil you probably don't have a START signal to the DME and thus the main relay won't close and there'll be no power to the DME. So you need to trace back and see why there is no power to the coil.

A 527 is simply a later version of the Motronic 1.3 DME. It will run the engine just fine.

[krazykraut]

After pulling the engine harness and going over it making sure I dont have any obvious problems, I started to trace my power lead from my battery. I have 12V from the battery leading up to my main power block terminal located on the passenger side of the firewall. Then, I have 12V leading from the firewall terminal to the fuse box. From the fuse box to one of the prongs in the bottom half of my C101 connector , I continue to have 12V. But, after comparing an 89 325, I noticed that the 89 has 12V leading into the fuse box, and 3V coming out at one of the prongs inside the C101 connector. Can anyone test their car and let me know what your reading is, or if this has ever been solved in another thread.

*I tested the bottom half of the C101 connector voltage with key in the "off" position**(on both cars with the same battery swapping back and forth)

[jlevie]

Start your trace for ignition coil power at the ignition switch and follow that through C101. The wiring diagrams from http://wedophones.com/BMWManualsLead.htm will be an essential tool.

[krazykraut]

Well after months of beating my head against the wall, I finally found the missing link to my spark issue. I didnt notice that I was missing the black insulation cup that keeps the distributor cap from shorting out. The PO had put his own contraption in to keep this from occuring. I had forgotten that had to buy a the cup..... Sooo the car build will now continue... I just want to say thank you to Jlevie and all those that had a suggestion as to what it could be.

[SpecM]

Well after months of beating my head against the wall, I finally found the missing link to my spark issue. I didnt notice that I was missing the black insulation cup that keeps the distributor cap from shorting out. The PO had put his own contraption in to keep this from occuring. I had forgotten that had to buy a the cup..... Sooo the car build will now continue... I just want to say thank you to Jlevie and all those that had a suggestion as to what it could be.

wait, what part were you missing?

[krazykraut]

http://www.realoem.com/bmw/showparts...20&hg=12&fg=05

Part #14 The insulation dish behind the distributor cap.

[jlevie]

That plastic piece is to isolate the distributor rotor from potenial oil leaks at the cam seal. It could be missing and not affect spark. Though if a field expedient fix for a missing shield was attempted, the "fix" could be a problem.