Won't start, no spark at coil.

[buzdof]

85 325e

I had to replace the 1-3 injector wiring and also for the t-stat housing temp sensors. I'm 100% sure I did everything correctly since I had wiring diagrams and another harness to compare with.

It won't start, I have fuel but no spark. The problem is that I have 12v at the coil, but I don't get any spark from the thing. I have tried two coils, but neither give me anything. I tried a different ECU, I looked at the fused link in the trunk (12v on both sides), and I double and triple checked the wiring I did. Any ideas?

Thanks

[kronus]

Check if you're getting a signal to the coil - place a test light on the excite wire and ground it. Should flash when you crank if the coil is getting a signal.

If it doesn't, there is likely to be an issue with your pulse and reference sensors. Check that their resistance values are in line with what they should be (960 +- 92 ohms, IIRC) at the ECU plug. Sorry, I don't remember what pins on the ECU plug these sensors are, but a Bentley manual should have that information.

[buzdof]

Thanks, I'll give that a shot after I eat some lunch.

Do the t-stat housing sensors have any control over whether or not it sparks?

[buzdof]

OK both have a resistance that is within the acceptable range (just above 1000) and I'm not getting a signal at the coil :(

[jlevie]

No ground pulse at the coil when cranking the engine will be:

No timing reference data to the DME
No power to DME
Bad DME

[buzdof]

I tried 2 different ECUs though, no difference...

[buzdof]

Also, why the hell would the main relay be warm to the touch even 45mi after I last tried starting it?

[SpecM]

Also, why the hell would the main relay be warm to the touch even 45mi after I last tried starting it?

hmm, shorted? check it out, and see it the DME is even getting power

[buzdof]

You bring up a good point, now I'm beginning to question (again) my meticulous rewiring. How do I check if the DME is getting power? I don't have my Bentley in front of me...thanks

[jlevie]

The Bentley probably won't be much help in this case. You need the full wiring diagrams and pinouts that are in the ETM. See http://wedophones.com/BMWManualsLead.htm

[buzdof]

Thanks for that.

I have power at pins 1 (when 'on') and 4 when cranking. So it appears as though there is power to the coil and ignition switch (duh, it cranks). I could not get anything from 35 or 16, which look like the power inputs. What does this mean? I've tried two different main relays...

Edit: It looks like it can ONLY get power through the main relay. Could I just jump two pins where the relay goes to force it "on"? Which pins would I jump?

[buzdof]

Can someone please verify that one realoem.com, part #12631710726 is the main relay?

[buzdof]

I'm so frustrated! I've tried switching DMEs, I put in a different wire harness, and nothing has changed. I'm still getting 12v at the coil, at the battery junction in the engine bay, and 12v at the starter. Although now the engine won't turn over...little bit of a step backwards. The main relay still gets warm when I have the key in the "on" position...


Edit: It cranks over now (I had the single plug starter wire on the wrong probe thing)...but even with the new harness, still nothing :(

[buzdof]

I get 12v from the coil to the distributor but still no spark. What the hell?

I'm starting to think that the magnet thing on the flywheel fell off!

[Farrington229]

buz i had the same problem and just fixed it today. check the main relay (under a small plastic cover next to your intake, one with the big red wire) and first off clean it, if it still doesn't start check if there's power to #30 and #86. if there is wire #30 to both #87s (at the same time) and turn the key. if you have the same problem as me then the car should start. i'm gonna replace the relay and hopefully that'll work :D. good luck man. hope i helped.

Andrew