B35 Swap cranking, no running

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careysd

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Got the Bav temporarily wired up last night to test motor. I can get it to crank, but no fuel or spark.

Key on, I hear the ICV humming.

Wiring list:

Bav/Motronic
Green/white to Green (Switch on)
Black to Black/Yellow (Start signal) engine does crank
Fuel pumps to Green/Violet (separately hooked up to 12V and got them to pump, doesn't work when hooked to computer)
Grounds attached.

I have my H2O and Oil Pressure hooked up through the original car wiring and they work.

Harness from an '87 or '88 E32 735 tha was running a 150 ecu. I am running a 179.

AFM from an '85 535.

I tried switching relays but it didn't help.

Any obvious mistakes before I start testing sensors?

Scott C.
 
I assume you checked fuel delivery (pull off fuel hose and crank) and spark?
On the earlier 1.1 cars there is also one wire on the separate three pin connector near the brain that has to be connected. Not sure on the later 1.3 harness...
 
I'd recommend you go back to the main relay checking for main power from bat and ignition at the plug. Get that going first.

Then make sure the ecu is powered up.
 
2 green wires need to be connected- 1 to the ecu and one to the coil through the engine plug.

Total of eight wire through the firewall..

1 green for ecu
1 green for coil
1 blue alt
1 oil
1 water
1 starter
1 fuel
1 tach
 
careysd said:
Harness from an '87 or '88 E32 735 tha was running a 150 ecu. I am running a 179.

Scott C.
Click to expand...

Woah, woah. Hold up. You are using a 150 harness with a 179 ECU? Did you verify that the DME plug pin-out matches between the 150 and 179 harnesses/DME's? Since Motronic 1.3 (179 DME) uses several different sensors from Motronic 1.0 (150/079 DME) I would bet they are different in several ways. If this is the case, you will need to either sub in a 179 harness or change the pin configuration of the harness DME plug to match the 179 harness.
 
No worries- the 179 ecu works with 150 harness, just not the other way around.
 
sfdon said:
No worries- the 179 ecu works with 150 harness, just not the other way around.
Click to expand...

It does? Ok then, never mind. Good to know.

Since you are using a 150 harness, does that mean you are getting crank position from the flywheel? Have you verified that the crank position sensor is functioning correctly? Since you bypassed the fuel pump control, one of the major things that causes a non-fire is the crank position sensor.
 
Thanks for the replies. Yes, 150, I believe is M1.1. I actually have two harnesses one from a 150 car and one from a 179 car. They are identical as far as I can tell.

I essentially just rigged it up to run to make sure the motor is good before I button it all up. This is why the water temp gauge and oil pressure are wire into the car vs. the engine harness.

Looking at sfdon's list, I may be missing coil wiring. The coil is wired up, but am I missing a dedicated 12V on the harness side (from the plug)?

I haven't had a chance to troubleshoot much, as it was late last night when I wrapped it up, but wanted to get this out there early in the a.m. so that other people, who may be better at it, might think for me! :-?

I think that since I hear the ICV buzzing and am getting the car to crank, I can rule out ecu or power to ecu problems (main relay)? Since there is no fuel or spark, I am guessing that it must be a sensor.

Also, all M30 AFMs are interchangeable, correct?

Thanks for the help, guys, I appreciate it!

Scott C.
 
All AFMs are different... different springs, different resistance values.
Just use an 027- easy enough to find.
You must have a dedicated green wire from your ignition switch to the coil and one to the ECU.
150 is 1.1
179 is 1.3
 
Lets make this simpler- with the key "on"- do you show 12 volts on any of the coil terminals?
 
Don,

With the key on, I get 12V at both coil terminals. With it cranking, I get no voltage at either coil terminal.

Scott C.
 
Are there 2 green wires at the coil on the bigger connector spliced together?
 
Yes, the larger terminal is the one with two green wires spliced together. I did have to extend these by about a foot to put the coil where I wanted it. I know that these wires are shielded, and the additions not, but I (maybe mistakenly) felt that wouldn't matter too much in this application.

I also verified the that the crank position sensor is connected to the terminal on the harness closest to the firewall, while the #6 spark plug reference is connected to the terminal closes to the radiator.

I tried to see if I could measure any voltage at the CPS while the engine was cranking, but came up with nothing. In all fairness, I am not even sure if this is the correct way to test this.

Scott C.
 
Measure the black and yellow wires with your voltmeter set on ac volts while cranking.
Keep in mind those connectors are easy to get backwards.
 
Hmmm... Black and yellow wires plural?

I have only one black/yellow wire hooked up (starter signal, key crank). There is only one other solid black wire coming from the plug and it is currently not hooked up to anything. Did I miss this one? (he says as he dives for the wiring diagram).

Or, are you asking me to check the voltage of the black/yellow (start signal) to verify proper voltage?

Edit: After searching, this small black wire is the tach wire, correct? This doesn't necessarily have to be hooked up to get a start signal?
 
Last edited:
I think he was talking about the wires inside your position sensors that you'd referred to....
From memore, one yellow, one black, one shield...
 
Tom has it right- each sensor has 3 wires -black, yellow and shield.
Cylinder id sensor doesn't need to be hooked up for the engine to run.
TDC sensor is needed.
Also check for resistance with connector unplugged.
 
Checked the voltage when cranking and when testing between the middle and end pin, I was showing voltage. It was jumping around, so I didn't see what the voltage was. But it was there.

Also testing resistance between these same two pins I showed around 500 ohms.

This leads me to believe that the CPS is good...?
 
have you tried swapping the plugs to the sensors?
 
Thought about it, but then the wires would be facing the wrong direction (plugs inverted). I should probably give it a shot, because this thing should at least spark or something...
 
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