'84 500 SEL electrical starter problems

I have an '84 500 SEL and for a few weeks it would stall once in a while when taking off from a light. Thought it was the fuel filter so when it just stopped working we replaced. Didn't work, had to tow car home.
Everything works, light, horn, windows, radio the starter turns over but the coil and ignition don't get spark. paid a mechanic to look at it and he said it needed an ignition control module (not cheap!) it didn't do a thing. Any suggestions? We would rather not do the hit and miss method as it can be very expensive and every part takes at least 3-5 days to get to us through UPS.
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Can it be the OVP relay? The one with a fuse on top? OVP does supply power to ECU (engine control unit) and it is known to die because of age. All such relays I have seen have date code on it. If yours is over 10 years old, definitely get a new one.
SingerMHG wrote:

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Ditto... even if you still need a ECU, you can get them rebuilt at much lower price.
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Have you checked the ignition switch?
The integrity of the wires to the engine from the switch? (A frayed wire could finally have broken from the motor's movement during acceleration.)
I believe a defective over voltage protection relay will allow the motor to start but then will go into the "limp home" mode as the motor warms up so IMHO the OVP is not the cause here.
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