86 BMW 535i ignition problem

[kais]

I was having intermittent ignition problem on my 86 BMW 535i (no spark).
Now it won't start at all. Checked the resistance on the coil, reference sensor and the ignition high tension wire all in spec. Changed the main relay and had the ECU unit rebuilt and completed continuity test for all the related points, still no life. What am I missing. Can someone help please. Kais.

[KC Ron Carter]

My WAG of the day is OBC relay.

You can connect the two green wires on the c2 connector and bypass it to verify it is the issue. That is how the OBC keeps the car from starting when a code is set.

Here is a diagram for reference.

[p beemre]

cheek your fuses, you never know. they get ceroded pritty easly! I had a simuler starting problem with my 85' 528e.
Hope you get it runing!

[kais]

Ron, I want to thank you for sending me the OBC relay schematic.
I had OBC relay problem about 6 months ago.I over came that problem by connecting a power source ( at ignition on ) to the green cable going to the main relay, bypassing the OBC relay. I could not find the OBC relay at that time because I did not have the schematic. Once I got the schematic from you I had no problem finding the relay. It turns out that the relay itself was good but the board had several cold solders, I reflowed those points and everything worked fine.But this was not the source of my recent problem. When the engine failed to start I checked everything including the reference and speed sensor.So I sent the ECU for a rebuild. After installing the rebuilt ECU back on, the car still would not start. Decided to check the sensors again and found that I had accidently swapped the cables during my previous trouble-shooting, which explained why it would not start after installing the rebuild ECU unit.Everything is fine now, I haven't had any stalling or engine not starting problem since installing the rebuild ECU unit and installing the reference and speed sensor cables correctly.

[kais]

By the way I did change all the fuses but that did not help in my case, thanks for suggestion though.