ETA No Spark

[blacksport325]

I've recently picked up an 85 325e that the previous owner states ran fine until they changed the cap and rotor (whether that is true, who knows). I am getting fuel, just no spark. I've checked the following:

-12.5V or so at the coil at the positive and negative posts when grounded on the car
-reference tab on the flywheel is there
-speed and reference sensors check out and are within spec
-I get ~10.5V at the coil and on the wire to the cap and rotor when cranking
-I've checked the pins at the ECU for a signal when cranking, I get voltage on the 3 speed and reference pins

It seems easy enough to say the brand new cap and rotor are bad, but I can't find in the Bentley on how to test those. I've tried another known working ECU as well, no luck. Unplugged the 13 button OBC in the event that was causing some sort of issue, no change. Any help is appreciated.

[blacksport325]

Bump. New cap and rotor and no spark

[101]

Has the car ever run for you?

Since you've already swapped the EDU, the next thing I'd try would be to remove the oil cap and make sure the cam is turning when cranking the engine. If you're getting fuel the reference sensors are doing their thing. If the cam is not turning, well, you know what that means.

Check the coil for proper specs. It could be weak or shorted out.

Check the spark plug wires foe excessive resistance - especially the one from the coil to the distributor cap.

If you have 12V+ power at the coil with the key on, something is either causing the ECU signal to fire the coil to not happen - or something is causing the spark to not be delivered to the plugs.

[blacksport325]

The cam is turning, it has not ran for me yet. New coil, New cap and rotor and New plugs with no change. The ECU must not get getting a signal to fire the spark. Looking through the Bentley manual now...any suggestions?

[blacksport325]

Looks like it's an issue with a relay. It started briefly and ran well. Its back to no spark again. The only thing I've touched to get spark is reseat the relays.

[jlevie]

You could have a bad main relay or relay socket., in which case the DME won't power up and there will be no spark or injector firing. A failing fusible link will also keep the DME from powering up. You can remove the backshell from the DME connector and check for power and grounds (see the ETM for your cat at http://wedophones.com/BMWManualsLead.htm)

If the DME is powering up and has proper grounds the next suspects would be the timing reference sensors, engine harness, and DME.