Another No Spark Thread (87 ETA)

[tH16]

So I still have no spark from the coil. I have a constant 12 on the positive AND the negative. No pulse on the negative. The reference sensor has been replaced but the speed sensor has not, but swapping the two does nothing.

I've read Jlevie's no start response over and over, and I have gone through and traced out diagrams in the Electrical Troubleshooting Manual. I have replaced the ECU, and the coil. Main relay is good. I have fuel.

Any other ideas? Something I'm missing?

[AsharC]

Check the fusible link on the positive terminal wire.

[tH16]

Checked that, as far as I can tell it's good.

[long tall eta]

all ur grounding straps attached?

[tH16]

As far as I know, where are the necessary grounds for the engine to start? Engine to chassis on the drivers side, starter ground?

[tH16]

Grounds should be good. I have 12v on pin 30 of the main relay constant hot, and pin 86 with key on. That should be powering the DME. Tomorrow I'm going to recheck the DME connector for power, grounds, and CPS inputs.

[jlevie]

The only grounds that matter in this case are the DME ground leads that connect to the passenger strut tower. If the engine to frame ground is bad, the alternator might not charge and/or the starter might not work.

If the DME is good, powered up and running, and both timing sensors are good the DME will ground the coil to make spark. You have changed one of the timing sensors (I hope with a new BMW part) and tried a different DME. Replace the other sensor with a new BMW part and verify that the DME is receiving power. Also check continuity from the DME connector to the coil negative post.

Note, if the replacement sensor wasn't a new BMW part, toss it and get a new OE part.

[tH16]

Correct me if I'm wrong but if the DME was not getting a signal from the CPS then I would not have fuel right?

[B-well]

Correct me if I'm wrong but if the DME was not getting a signal from the CPS then I would not have fuel right?

correct.

the problem is the on board computer relay box



this gives signal to the dme to fire the coil. DME should hum if not this is the problem

[tH16]

Edit

[tH16]

EDIT: on the ETA the OBC relay only connects to the Main relay, which runs power to the DME.

[B-well]

EDIT: on the ETA the OBC relay only connects to the Main relay, which runs power to the DME.

i wouldnt tell you if i did not have the exact same problem.

tested all circuits on the DME plug per the bentley and the fusible link ect all passed with flying colors

got fuel but no spark with both coil terminals hot+.

replaced the obcrelaybox and started right up

[tH16]

Alright I'm not opposed to trying anything, what's the proper test procedure for that relay?

Also JLevie, the ETA DME connects to the left side of the engine block according to the ETM, but I will be checking that.

[B-well]

Alright I'm not opposed to trying anything, what's the proper test procedure for that relay?

Also JLevie, the ETA DME connects to the left side of the engine block according to the ETM, but I will be checking that.

swapping it out is the easiest. theyre very cheap

ill get the test procedure when i get off work

[tH16]

I jumpered the green and green red wire. I had spark and the car started but shut right off. Pulled plugs and put them back in. Now I'm back to no spark off the coil.