Importance of functioning donuts, cyl. identification sensors M70
I just read in the German forum about a case where someone changed on his M70 distributors, rotors, spark plugs and ignition wires on cyl. 6 and 12 and used the re-old donuts. Then he had trouble. Engine starts, runs short time with increased RPM and then dies. EML lamp goes on with ignition on and then goes out again as it should be. Diagnosis faults: fault ignition cylinder 1-6 and 7-12. That was 2 weeks ago. Today he fixed it. He noticed that he installed the cylinder identification sensors/donuts/pulse generators on ignition wires cyl. 6 and 12 the wrong way. Turned the donuts the correct way and engine runs starts and smooth.
Apparently there no direction marks on the original ones, if I remember correct.pics from ECS website, original https://www.ecstuning.com/b-genuine-...e/12121725020/
Aftermarket pics based on boodmo info : Facet 9.0103, ERA 550277, MEAT & DORIA 87418, SIDAT 83357, Hoffer 7517418
This is not the first time that I read that when donuts are not working properly or the ignition wires/plugs # 6 and 12 are not functiong, there will be engine problems.
So if the M70 starts, idles for some seconds, then dies, also check the ignition wires, plugs and donuts from cylinder 6 and 12. The usual cause of running for a few seconds and then stopping is the lack of cylinder identification signals. These are provided by the inductive sensors on HT leads 6 and 12. When you get a fault with INPA ti-signal, this is the injection time signal, the base timing is derived from the cylinder identification signal. We had the same problem some years back on an 850: lack of cylinder identification signals. In our case the ignition wire boot of cylinder 12 was lose/not connected to the spark plug. Before we checked the usually subjects like fuel pumps, fuel pressure, ignition = distributors + rotors, crankshaft position sensors.
The car is telling you what is wrong, the CID sensors... Make sure you have them plugged into the right plugs? Make sure they are actually any good? Bad "donuts" have been a common problem with some replacements...(aftermarket).
Another comment: Friend had same sort of problem a while back, motor would start and then died shortly thereafter. He'd brought it used from out of state. I had a suspicion after listening to the motor start and die a few times that not all cylinders were firing. I took a look and found they were from a 3 series! Popped in a spare set from an M70 and the car fired up and purred like a kitten. Turns out original owner sold car because it kept shutting off.
So important is, when you change ignition wires and re-use the old donuts, make sure the donuts are installed the same way as original, not flipped. Basically it is not possible to installed them the wrong way, because the donut inner ring is conical and not round, so it should go onto the wire only one way. but some apparently squeeze it on the wrong way.