SOLVED 1981 M30B32 Motronic 1.0 start issue.

E28 technical advice asked and given! Troubleshooting, modifications and more.
tschultz
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Joined: Mar 01, 2009 7:58 PM
Location: Denver, Colorado
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Re: 1981 M30B32 Motronic 1.0 start issue.

Post by tschultz »

Engine block to battery!
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

Thanks tschultz!

Will try to connect one at the time to understand the changes/improvements.
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

Question (might be a stupid one)...

Is there any difference on the engine harness between an automatic & manual transmission on early models of Motronic (e.g. 1.0)?

Bo
jupdown
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Joined: Mar 11, 2020 1:04 PM
Location: CA

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by jupdown »

Measure ac voltage on the reference sensor and speed sensor pins on the wiring harness from the ecu. I don't remember the pin number off top of my head, but ref. Sensor should read around 0.4 volts ac and the speed sensor around 4 volts ac. Also check volts to the starter from the same harness should be around 12ish volts. For the sensors this will guarantee that the sensors are connected correctly, so the ecu gets the proper signal. I know because I had the same issue (no spark). And I swear I check multiple times before, except the way I described above.
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

jupdown,

thanks for your input and proposal.

I have measured both sensors (position & speed), also the starter motor. ALL measurements has been done on the pin outs (wires) while connected to the ECU. Please see my values below (bold), which I see differs from what you are mentioning.

Question: Are my values to low? Could that be a reason of NO spark?

Pin #. function------------------------------------------Ign. OFF-------Ign. ON----------Crank

4. Starter Motor--------------------------------- 0 V--------------0 V----------------8.6 V

8. Crank speed sensor (1)----------------------0 V--------------1.4 V--------------1.8 V

25. Crank position sensor (1)----------------- 0 V--------------1.1 V---------------1.5 V
26. Crank position sensor (2)----------------- 0 V--------------1.1 V---------------1.5 V
27. Crank speed sensor (2)-------------------- 0 V--------------1.1 V---------------2 V


It would be very interesting to hear your thoughts.

Bo
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

Gentlemen!

There has been very little work done in the garage lately.... But now I'm up n running.

I now need some help from you ECU wizards!

Question

-What makes the "Ignition Timing Control-coil output" switch ON/OFF?


I assume that the ON/OFF function for the "coil output" internally ECU is controlled by the Crank position sensor" by indicating the pin on the flywheel.
If my assumption is correct, i have on one side a signal going from the "coil output" in to the ECU, on the other side i have a signal going from the "crank position sensor" in to the ECU. What I uncertain about is WHAT happens internally in the ECU? What might be broken internally ECU if the signals between "coil output" and "crank position sensor" don't mate?

Would appreciate your expertise and thoughts!

Bo
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

It RUNS!!! :cool:
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

Image

Recently 3000 km.... Runs like a dream!
Chrisdude88
Posts: 1
Joined: May 28, 2022 5:07 AM
Location: Australia

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by Chrisdude88 »

Just stumbled across your post and I'm having the same issues with a converted 633i what was the outcome. How did you solve it. All my pin data seems very close to yours it's driving me nuts
chrome75
Posts: 29
Joined: Aug 02, 2020 6:15 AM
Location: Netherlands

Re: 1981 M30B32 Motronic 1.0 start issue.

Post by chrome75 »

Chrisdude88,

without knowing your exact issue i can tell you what mine ended up in.

Issue areas:
-Main relay/Start relay => No function => Didn't have an OBC in my car so I had to rewire directly from ignition switch to ECU wiring
-ECU => High voltage ignition coil driver not working. Internal ECU component that manages the "coil output" and "Speed sensor" signal (crucial for spark)
-Distributor cap => Cracked
-Rotor => Cracked
-Grounds => All my ground cables were old. New sturdy groundings: 1. Chassis to battery neg 2. Chassis to engine block 3. Chassis to cyl. head 4. Chassis to bellhousing (i think...)

Let me know if you have any questions.

Bo
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