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I ran both tests, and they both did not give me a spark.
I am going to pull the coil off my 90 740t and swap it.
I wiggled the wiring plug in the passenger kick panel and the plug under the hood to what I think is the ICU. The ICU plug was filthy and filled in/up with what looked like old vaseline. Maybe it was dielectric grease.
I cleaned it out, hoping it was contributing, but no dice.
What next?
Is there a way to test the hall sensor itself without using any other components? Like a conductive test for the TPS. Maybe if I run a small current through it with my ohmmeter, and use the feeler gauge, it will change the flow of current. I think that's how a Hall sensor works. Induced current... where's my physics book? ;)
Is this right for the spark steps?
Hall sensor tripped
ICU trips coil
Coil sparks.
Wiring from Hall switch to ICU has to be intact. Wiring from ICU to coil has to be intact.
I doubt it's the coil. From what I remember they're very robust. I disconnected the leads one at a time, and the red lead and black lead arced when rubbed on their contacts. The Thick white pair(?) of wires did not arc. I think that's the signal wire.
Does this car have a power-stage amplifier like my LH 2.4?
Back to it. Going to replace the coil. Then I would replace the wiring, but I don't have a pinout for the wiring. The wiring actually looks somewhat sound to me. Anyone know which pins correspond to the 3 hall effect sensor pins?
If all that fails, I think the next logical step would be to replace the ICU, much as I hate to throw parts at a problem. Is there a test I can do with a multimeter on the ICU?
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1990 740 Turbo, on its way to stock specs, maybe beyond
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