M30B35 Engine Wiring Issues - Won't Start

[M M 250]

I am having a starting issue with the M30B35 in my E28. I'll start from the beginning so that all the details are here. When the motor was in the E34, the fuel pump was jumped between the ignition 12v pin and the pump power wire to get it to work. I tried a relay (which was unknown condition) to see if it would work but it did not. The car also developed a very bad miss just before I pulled the motor out until the day I drove it to the place I was working at to pull the motor out. What would happen is the car would start ok but missed and backfired under throttle, the more you pressed the worse it was. It was driveable cold but got worse as it warmed up and became pretty much undriveable when warmed up.

The day I was driving to pull the motor, it stalled on me a block from the place. I tried to start it but it wouldn't fire and the battery went completely flat. So we towed it. Once there, I jump started it to see if it would start and it started a bit rough, then came to life and ran perfectly. Drove it up and down the road a bit and it ran without a single issue. So I took it inside and pulled the motor.

Once the engine was in my E28, when we first started it, it ran rough like it did in the E34 when it was missing. I fiddle around a bit, left it for a day with the battery disconnected and then the next day it started up fine. Ever since then the car was running fine, except for a slight miss at low revs, until I pulled my gearbox off to change the clutch. When I put it back on, it did the same thing. It ran rough and missed, so I let is sit for a couple hours with the battery disconnected. What do you know, started up and ran perfectly fine.

Last weekend I decided to swap the loom and DME to see if it would solve the fuel relay issue and other issues like the ICV not working at all. It gets 12v to all 3 pins with ignition on. The fuel pump relay gets 12v to all pins when key is in except ground which is grounded, yet the relay (tried 2, one was definitely good) does not work. Anyway, so I swapped the loom and DME, turned ignition on. ICV buzzed as it should. Then I tried to start the car. Nothing. It cranks but will not fire. I triple checked everything and even tried my old ECU, still nothing. ICV no longer buzzes but gets 12v at all pins. Grounds test at 12v, however the coil only gets 9v. I ran a relay for it to test but that only gave it 10v, even though the power wire was a completely new one. Also tried different coil, still nothing. Took my crank sensor out and tested it on my friend's M30 and it worked perfectly fine on his car. All issues the same as with old loom. So I swapped my old loom back on and still have the same issues and won't start. It am 99% sure the DMEs are fine, will test on another car to be 100%.

Is there anything else that could cause the car to not fire? One other issue I've had since the car had an auto on the 2.7 is that it won't turn over on the key occasionally, especially when the engine is hot. But this could be bypassed by starting it through the diagnostic port, which worked every time on both the old motor and this motor. I tested today and the starter trigger wire only gets 6v when the motor won't turn, but gets 11.9v when it does. I know this issue is unrelated however I don't know if maybe because of this something is not getting a signal and therefore not starting. But it seems odd that all of a sudden there is a problem.

Sorry for the long description but I felt that the details could be necessary.

TL;DR: Engine always had some odd wiring issues but ran, swapped harnesses and DME and car wouldn't start. Swapped back to old harness and still won't start. I semi-admit defeat and would appreciate help.

Edited June 15, 2016 by M M

[User Name 19]

If you need the wiring diagrams etc just to double check i have them around as i have done same conversion but my engine was out of 7 series but same deal. There is a webpage but cant seem to find link

What version of Motronic are you running?, as if i remember right 1.3 it has a basic self learning function and also an emergency mode

To me personally it sounds like its either gone back to base after you take battery off and ecu battery dies, then takes around 200km (did on mine before it stopped playing games after conversion) eg. misfires, bad throttle responce etc

I have also dealt with emergency mode = engine runs like dog due to faulty sensor or out of fuel or wont run at all.

I know this isn't the most helpful but plenty of guys on here have good knowledge and as we all know gremlins are always afoot

[M M 250]

Thanks for the reponse. Those diagrams would be very useful if you can, would like to check pinouts etc of some plugs and see what's happening. Yes it's Motronic 1.3, both ECUs are 179 type.

[User Name 19]

Hey,

My old post - http://bimmersport.co.nz/topic/22064-wiring-conversion-e28e32-final-steps/

Attached some documents i have as well....

I am still looking for the website with the full conversion has pics and everything but for life of me my internet histroy isn't brining it up so must have some weird title.

Hope it helps

motonic Stuff.zip

[M M 250]

Thanks man, will have a look through it later. Are you refering to the mye28 thread by any chance?

[eliongater 718]

Is this any use to you?

http://www.e30zone.net/e30zonewiki/index.php/Engines_Troubleshoot

It helped me diagnose a faulty ignition switch. I'm currently in the middle of converting my 525e to motronic 1.3 (I got it running, just need to time to tidy up) and will be putting an m30b35 harness and ECU on my m30 for my m535i.

[M M 250]

I've done pretty much all those tests unfortunately.

At the moment I get the following:

8v at the coil.

On the pins on the crank position sensor:

Yellow wire:

-Key on: 0.02v

-cranking: 0.15v

Black wire:

-Key on: 0.06v

-Cranking: 0.16v

Shielded wire:

-Key on: Jumps between 0.01 and 0.02

Cranking: 0.16v

Looks like it's not getting signal power but at the ECU pin 6 (which I found is meant to be the output) is putting out 12v. Also can't find continuity for the black or shielded wire to anywhere on the ecu plug. Yellow wire, pin 47 is the only one that has continuity.

As a side note I tested the sensor on a friend's M30 and the car worked fine so I am fairly certain the sensor is not to blame.

Edited June 22, 2016 by M M

[M M 250]

Found a good site with all the pinouts for heaps of BMW ECUs.

http://www.e30zone.net/e30zonewiki/index.php/ECU_Pinouts

Tomorrow I'm going to try a relay for the coil to see if I can get it to 12v and see what happens then.

[M M 250]

Tried to power the relay by coil today but made no difference. Is there any other sensor other than the crank position sensor that can stop spark? It's definitely getting fuel.

[BM WORLD 1286]

Tried to power the relay by coil today but made no difference. Is there any other sensor other than the crank position sensor that can stop spark? It's definitely getting fuel.

have you got spark at the coil lead but not at the spark plugs leads?

ecu ??

[M M 250]

have you got spark at the coil lead but not at the spark plugs leads?

ecu ??

Not sure actually, I need to test that. Coil definitely has voltage though and I tried 2 different coils.

Tried 2 different ECUs, both doing the same thing. It is outputting signals and voltage as it should be based on the pinout diagrams I have found but seems like it's something to do with the crank sensor, but I can't figure out the issue. Where does the crank position sensor get it's input from? Doesn't seem to be a pin on the ECU. Does it use a 12v+, 5v+ or negative signal? I'm wondering if I jump the input pin will it get it to work for diagnosing purposes.

Edited June 23, 2016 by M M

[BM WORLD 1286]

Not sure actually, I need to test that. Coil definitely has voltage though and I tried 2 different coils.

Tried 2 different ECUs, both doing the same thing. It is outputting signals and voltage as it should be based on the pinout diagrams I have found but seems like it's something to do with the crank sensor, but I can't figure out the issue. Where does the crank position sensor get it's input from? Doesn't seem to be a pin on the ECU. Does it use a 12v+, 5v+ or negative signal? I'm wondering if I jump the input pin will it get it to work for diagnosing purposes.

crank signal wire goes straight to the ecu , then the ecu will do the pulses to the coil and out put to the injectors and output to switch on the fuel pump relay

[M M 250]

crank signal wire goes straight to the ecu , then the ecu will do the pulses to the coil and out put to the injectors and output to switch on the fuel pump relay

Ah, that makes more sense. So where does the shielded one from the crank sensor go?

[M M 250]

Over the weekend I tested the ECUs on a friends car, work perfectly fine so that's not the issue.

I also went to check the ignition lead from coil to distributor, the lead is fine but the post of the distributor had broken off, however the contacts were still together. In any case I swapped it with a replacement but the car still doesn't start. Last test I need to go is if a plug sparks straight off the coil, I will test this tonight.

Also charged the battery and the coil was getting full 12v again. I tested the crank position plug and it gets 5v to the bottom pin now, same as on my friend's M30 so that seems ok. Might have just been a low battery before.

My only other thought, there are 2 wires that connect to the starter motor. Are one of those a signal that is needed for start? Apparently that's an unloader wire so doubt that has anything to do with it.

Otherwise I have no idea what to do with this car and might just have to convert to Megasquirt or something. I don't like fixing things like that but I am really stuck with this.

Edited June 26, 2016 by M M

[BM WORLD 1286]

early motronic ecu is a very simple system

needs power , needs a crank signal

outputs to the injectors and fuel pump.

afm , temp sensor help with the fueling amount etc.

needs have good earths , a good 12volt battery .

[M M 250]

early motronic ecu is a very simple system

needs power , needs a crank signal

outputs to the injectors and fuel pump.

afm , temp sensor help with the fueling amount etc.

needs have good earths , a good 12volt battery .

I know, which is why I am so baffled by this. It has everything it needs to run, yet it won't.

[M M 250]

There is actually one other thing. I had to extend the two wires (one shielded) that go to the coil so that it would reach. I just cut the wires and soldered a longer bit of wire and put a crimp but on the end. This worked fine the first time round when I initially did the swap. However, is there something that could cause an issue here?

[M M 250]

Just did some more testing. With a spark plug hooked up to the coil lead, there is no spark, except for when I turn the key off, it does a quick one.

The crank angle sensor only has 5v on the bottom pin (black wire) when unplugged, when it is replugged, there is 0.1v and no signal.

ICV has started working again.

Thinking I might jump a pin off the AFM or something that has 5v to the crank sensor and see if that helps.