Montonic question - help needed PLEASE, 1987 E30 - BMW Forum -

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post #1 of 4 (permalink) Old 02-29-2012, 10:44 AM Thread Starter
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Montonic question - help needed PLEASE, 1987 E30

Hello All !

Just joined because I found similar threads searching for info - some of you are very sharp and I would appriciate your help big time.

I just bought a 1987 325IS as a project restoration and had it shipped to me . It was running but blew a freeze plug - perfect b/c I can fix easy and got it for great price. I planned on instant rebuild anyway.

It was running when they loaded it on the trailer. The car had blown a freeze plug so they ran it just a min to get on truck. when It reached my home I just pushed it in garage and began the tear-down.

I went to town on it, 2500+ dollars in new everything - after doing a complete timing belt job, tune up, valve adjustment -total freshen up of engine minus pulling head and pistons (next month).....
I tried to start it. I wouldn't start - no fuel pressure. Went through my Bentley book did tests and fuel pumps run with jumper. Voltage is coming to relay -so I changed out the fuel pump relay and main relay. Still did not start - bench tested relays and they click and close circuit fine. but when you stick relay in car socket, with voltage present - no click, no fuel pump.

What I found is that the 12 volt side of fuel pump relay has + power signal to close - BUT the ground brown negative side is not there, ungrounded - no continuity to ground. If you have the relay in place and jump the ground wire to chasis from under the socket - relay and pumps operate. (socket is good)

That leads me to the Montronic ECU - that brown wire ground goes to it. Also the relay next to it (lights)and the main I believe do not have ground connection. (however lights will work)

I followed ground troubleshooting on Montronic with Bentley manual - some of the ground continuity checks came up bad (open). I looked at all the ground connection points on the car - everything looks good - leaving me to ask is it the Montronic unit that is bad ? Does it use those ground wires to signal the various functions ?

Even with the fuel pump running by jumper wire - the car doesn't start leaving me to believe the injectors are not being told to fire either. Some interior functions are not working although fuses are good, like power windows and some lights, little computer read out, etc - some functions work fine and car will turn over all day. (later today I will check for spark but don't think its there)

Another thing funny is with ignition off, I read continuity to ground from several of the fuses in fuse box - all that should be isolated 12+, making me think there is a ground somewhere.

Would the montronic going bad / being fried cause all this confusion ?

There were also indications that the cars battery could have been put in backwards at one point, the large wire from alternator to starter + was burned. I replaced it and closely inspected and repaired any damage to wires touching that burnt one. Would that fry the montronic ?

All fuses are good, changed out, fuse link good, relays all new - and this no ground in montronic wires seems to be keeping car from starting / running.

Help please ???? Any ideas ??

I have this beautiful E30 sitting in garagefreshly tuned with new 17" Beyern mesh wheels, new brake kits, coil-overs, all new grill, fresh painted engine - shes just beautiful and ready to go......but wont start and I'm pounding my head at this point !
Thanks so much for your time - I'm stuck

PS - to make things more confusing, when reading Bentley manual I noticed I had the Montronic 1.1 updated version ECU with (50)? pins - but the plug has less pin connections and wire harness looks like there are possibly professional factory like splices....this model year 325 is right around the date they were swapping to the 1.1 version - did I end up with a hybrid assembled car / wire harness adapted to run on newer Montronic 1.1 ?????? aaagghhhhh

Thanks !!!! Garet
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post #2 of 4 (permalink) Old 03-01-2012, 05:24 AM
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Welcome to the Werkz.

Reversing the battery posts could cause all sorts of issues with the electronics, some of the issues could be intermittent.

Jumper the fuel pump and then check the injectors when you crank then engine over with a mechanics stethoscope (listen for the clicking). Check for a spark as well. If the injectors are firing and you have a spark, then you are more than half way way there.

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post #3 of 4 (permalink) Old 03-01-2012, 09:48 AM Thread Starter
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Hello Brettski - and thanks for the welcome and reply...I was hoping to hear from you I read some good help on other threads from you and the guys.

So I put a noid light on #1 injector plug this AM before work to make sure -

When I connected the neg battery cable the car starter took off on me - out of control car starter....
It did that a couple times when I was testing the Montronic a couple days ago as well.

When I was testing the car before as I mentioned, I had the fuel pump jumped and running, and tried to start the car - it just cranked over and nothing - so I am quite sure there were no sparks.

Good news is I have a montronic ECU reman showing up today from Pelican parts, next day air.
So - I will slap that in and see if thats the issue.

Whith all that chaos going on - does it sound like the ECU to you ? I think so...

Any warnings about anything before I puit the new ECU in ? ( I know about static handling etc) I am worried about some possible short because of this run away start issue now. Hopefully its just a scrambled ECU thats causing all the weird stuff.

Thanks so much for your help and advice !!

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post #4 of 4 (permalink) Old 03-03-2012, 10:05 AM
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I would suspect ECU (ECM) is the fault... Or at least the signals it employs !
Change of polarity can have disasterous effects to critical components such as the engine management.
Find a working ECM and swap over to test, just to ease our suspicions !!

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