BMW E28 no spark – ignition faults
What should I measure on the E28 ignition coil and inductive sensor when there is no spark?
The coil's primary winding resistance is about 0.82 ohms and the secondary winding about 8250 ohms. The inductive sensor in the distributor (which tells the control unit the spark timing) has a resistance of 900–1200 ohms.
What usually causes a lack of spark in the distributor?
The sensor wire can break at the side of the distributor, the sensor tips can bend into contact with the body, or the distributor's centre hub can seize. Keep the distributor cap and the control unit connector dry.
How can I test the inductive sensor?
The sensor's signal is alternating voltage that swings between -12 V and +12 V, so you need an oscilloscope or an analogue meter. The resistance between pins 5 and 6 of the control unit connector should be about 1000 ohms.
What else should I check if there is no spark?
Check the order of the ignition leads (firing order on the M10 is 1-3-4-2) and the injection ground wires on top of the intake manifold. The Motronic control unit relay can cause an intermittent lack of spark.