MM70 Woes, one bank no spark

Hi Guys, have built an E34 Touring with an M70 engine out of the E32 750iL. There is a thread here in the E34 section if you are interested, you can search there! The car is 100% complete and I have been driving it around for over 3 months now with no issues, untill last week! as much as possible, the E32 body and engine etc looms were transferred to this vehicle

Was driving the car and then all of a sudden total shut down of the engine. have eventually figured out that one bank is shutting down on start up and killing at fuel pump as its designed to do. however had the fuel lines connected back to front so it killed the fuel pump that is connected to the other bank.have swapped those around and now the engine will start and run as a straigh 6 on the drivers side. however the passengers side doesnt run, and will not generate spark.

here is a list of what I have tested so far and prooved to be fine. in most cases, this is just a case of swapping from the left bank to the right bank and vise versa to see what happens.
1/ coilpack
2/ leads
3/ afm
4/ dizzy and rotors
5/ fuel pump relays
6/ main relays
7/ Crank position sensors, one is at ~570ohm the other is at ~540 ohm, supposed to be 520ohm +/- 10%
8/ these ratings read at not only the cps's themselves, but at the pins connecting directly to the ECUs pins 46 and 47
9/ ECUs getting 12V on pin 18 all the time
10/ ECUs getting 12V on pin 37

i think thats just about all that I have tested!

what are the other classic no start issues with one or other banks with this engine that I havent thought of, other than the ECU for that bank itself being fried?

Originally Posted by _Ethrty-Andy_

Hi Guys, have built an E34 Touring with an M70 engine out of the E32 750iL. There is a thread here in the E34 section if you are interested, you can search there! The car is 100% complete and I have been driving it around for over 3 months now with no issues, untill last week! as much as possible, the E32 body and engine etc looms were transferred to this vehicle

Was driving the car and then all of a sudden total shut down of the engine. have eventually figured out that one bank is shutting down on start up and killing at fuel pump as its designed to do. however had the fuel lines connected back to front so it killed the fuel pump that is connected to the other bank.have swapped those around and now the engine will start and run as a straigh 6 on the drivers side. however the passengers side doesnt run, and will not generate spark.

here is a list of what I have tested so far and prooved to be fine. in most cases, this is just a case of swapping from the left bank to the right bank and vise versa to see what happens.
1/ coilpack
2/ leads
3/ afm
4/ dizzy and rotors
5/ fuel pump relays
6/ main relays
7/ Crank position sensors, one is at ~570ohm the other is at ~540 ohm, supposed to be 520ohm +/- 10%
8/ these ratings read at not only the cps's themselves, but at the pins connecting directly to the ECUs pins 46 and 47
9/ ECUs getting 12V on pin 18 all the time
10/ ECUs getting 12V on pin 37

i think thats just about all that I have tested!

what are the other classic no start issues with one or other banks with this engine that I havent thought of, other than the ECU for that bank itself being fried?

If all sensors are ok, and no spark it means smth wrong with that bank ecu
Did you try to swap them?

no have been told that they are bank specific, are they not? id rather not find out the hard way. Fuel pumps both prime however, and also work for a second or two on start up, but then the pump feeding the left hand side is shut down of course.

also, the spark sensor on the number 6 and number 12 cylinders, what is the best way to test these?

i have no continuity between the dizzy end and any of the three pins, the spark end and any of the three pins, or between any combination of the pins themselves except 1 and 2 which are at 0ohms? Im just about to walk out the door and go down to my lockup and test the lead itself even though ive done it before and see what happens.

Without spark plug sensor you won't get any spark.
Well I would try to swap ecu first, though it might be aligned with ews.
Spark is initiated by ecu if it gets crankshaft signal, also it's a good idea to inspect that distributer cap or replace it with new one from other bank.

no EWS on this vehicle which is good. all leads are around 5-6kohms, and donuts give the same readings for each sensor on both banks so assume the one for the keft hand bank is fine too.

continuity from ecu/loom plug to those pins on the front of the engine, also continuity to the coils.

Test for spark with a grounded plug and a coil from each bank. If you dont see a physical spark, then it is the ecu for that bank as everything else checks out.

There should be no undue issues swopping ecus. If they cannot be swopped, the computer clamps on top will not fit...they would be made that way deliberately.

Wouldn't the firing order be backwards if the ECUs are swapped? But it does seem It's the ECU tho.

The firing orders are informed by the respective crank sensors. In any case they built the same ecu twice i bet and the software knows which bank it serves by the wiring attop each clamp.

As incredibly intense your swap is everything is basically e32/e31 specific. I'd travel over the those sections to get a more definitive answer. Or even over to BF.C's two sections. For unless some else has the exact same swap your answers will be general at best. You need specific information.

I'm subscribed for I may attempt this swap for the hell of it.

On the other hand there was an old thread at Bf.c e34 section about a similar swap over in malaysia. I don't think dude is active there or here. But his notes are over there. He may have run into the same issue. I'd check it out.

Found his thread off site:
http://www.euroasians.net/category/my-euros/my-e34/

He'll probably have some answers for you

Well fantastic, i got this car sorted! Ill only post here as follow up to say that YES the ECU/DME are cross compatible side to side, and one of them had died. very strange, and i need to determine why it died, but for now its great and a good and proper V12 again!


Edit: just realised I posted this in the E34 section! no wonder i didn't get heaps of help haha. just had this page open on the iPad in the garage and never closed it just kept updating!

Originally Posted by SFbay

Without spark plug sensor you won't get any spark.
Well I would try to swap ecu first, though it might be aligned with ews.
Spark is initiated by ecu if it gets crankshaft signal, also it's a good idea to inspect that distributer cap or replace it with new one from other bank.

Originally Posted by robertobaggio20

Test for spark with a grounded plug and a coil from each bank. If you dont see a physical spark, then it is the ecu for that bank as everything else checks out.

There should be no undue issues swopping ecus. If they cannot be swopped, the computer clamps on top will not fit...they would be made that way deliberately.

Originally Posted by robertobaggio20

The firing orders are informed by the respective crank sensors. In any case they built the same ecu twice i bet and the software knows which bank it serves by the wiring attop each clamp.

Originally Posted by _Ethrty-Andy_

Well fantastic, i got this car sorted! Ill only post here as follow up to say that YES the ECU/DME are cross compatible side to side, and one of them had died. very strange, and i need to determine why it died, but for now its great and a good and proper V12 again!


Edit: just realised I posted this in the E34 section! no wonder i didn't get heaps of help haha. just had this page open on the iPad in the garage and never closed it just kept updating!

Yup, looks like you didn't get heaps of help alright.

Originally Posted by robertobaggio20

Yup, looks like you didn't get heaps of help alright.

what i mean was more people posting their ideas

Originally Posted by _Ethrty-Andy_

what i mean was more people posting their ideas

But we were right, and very early on, which is what matters. Quality*, not quantity, a hallmark of the BMW 5 series.....


* Before you say it, this does not necessarily imply brevity, BMWFF sir

glad you got it all sorted out.

Originally Posted by MySatinDoll

glad you got it all sorted out.

Yes, he is certainly glad that he got it all sorted out.

might have to take the fuse for the ABS out and pop a skid