Bad ECU?

[kickinindian]

so my car finally kicked the bucket after it had a random no start problem for some time. i have changed the CPS, Main and Fuel relay, i jumped the 30 and 87 pin to start the fuel pumps to test fuel pressure and it is good. both pumps work, when i try to crank the car, no spark or fuel.
cps had correct readings and was running 5min before it stopped starting, turned it off and wont start again. im thinking its down to a bad ecu.
when it was still starting it ran perfect, newish plugs and stuff im just out of ideas and i really need something besides the whole check the CPS, Main relay, stuff. ive been told before as those are all working and new.

CAR Is 1986 325es 5spd

edit: i also cranked the car without the ECU harness plugged in and nothing changed it cranked but did not start hence why i think its a dead ecu.

[jlevie]

The timing reference sensors can ohm out okay, but still not work. In this case new OE parts would be the first thing I'd try.

[kickinindian]

Yea i have a new bosch one in and it still does not seem to have changed anything...so im looking all over options :/ it just is interesting when i unplug the ecu it acts the same way like it does when it is plugged into the ecu

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[kickinindian]

Im plauing with the afm right now soo maybe that could be it

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[kickinindian]

Mine was when i turn it off it will not start again. Except once tonight when i tried it without touching anything for 4hours started up once turned it off now it wont start again.

edit: i plan on going to PnP tommorow morning to grab one or 2 and test it out but i just want to see if anything else could be a problem im going to grab a coil and some spark plug wires as well to see if that could be it. as well. still does not explain the no fuel problem though so it has to be sensor or dme problems right?

[jlevie]

The fuel pump is controlled by the DME and only runs when the DME sees timing data from a rotating engine. The DME also generates spark using the timing data. No spark and no fuel when cranking will be:

A problem with DME power/ground (bad main relay, bad fusible link)
No timing data to the DME (bad sensors, bad engine harness)
Bad DME

[kickinindian]

Okay thanks so since im pretty sure my sensors are good im going to grab an ecu and see what that does. If not ill check the harness at the harness ecu side. What should i check on the ecu plug?

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[kickinindian]

So i got the new ecu lwt it run for10min or so and it ran fine my friend pushed on some wires that lead to the coolant temp wires and the car shut off after it bogged down when he pushed on them and now i cant get i to start again an ideas? I thought the car could start without coolant imputs?

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[101]

1) Smack "friend" upside the head and tell him/her to keep their mitts off your engine.

2) Based on the immediate problem right after those wires were touched, you could have a loose connection at the coolant temperature sensor. The sensor has low resistance when hot and higher resistance when cold. If the wiring there is loose and the DME sees high or infinite resistance from that sensor it will dump fuel into the engine thinking it is cold. I don't think the engine will run with it completely disconnected but I could be wrong on that point.

3) I'd recommend a complete check of every sensor and a complete check of the wiring all the way back to the DME by doing the checks at the pins of the DME connector. This rules out any bad sensor or wiring (except the crank sensors which can be flaky even when passing the resistance checks as JLevie said). The Bentley manual is your friend here.

4) You mentioned that you changed the crank sensor. There are two. Might be worth substituting the new sensor at the other position.

5) Double check that fusible link and the condition of the grounds as JLevie suggested.

I chased an intermittent no-start for a year on an 87 eta. Its frustrating as hell. Mine did eventually turn out to be a bad DME.

Good luck!

[kickinindian]

i think im going to make another run to the PnP and pull an eta engine harness, hopefully from an 86 and see if that is it. the PO looks like they spliced connectors to the coolant temp wires and im thinking that might be messing up something. also im missing the wire running to my fuel pressure switch(the one with the single wire). so i figure try a better harness and see if the harness was just beat up.

And if that does not work out i might just look on swapping to 1.3 and do that since im already going to be switching most of the wiring

edit: also found this, http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf so i will read this and use it when i go out and work on it tommorow

[bddog]

Two new cps. I bet you it starts

[kickinindian]

The top one? I thought it only needed tje bottom one to start. Ill try it though

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