I agree with JimmyL, don't like that wiring hack job, could be part of your problem. If you can, get a correct wiring harness, and install properly, or make sure there is no short. On a non turbo engine, the starter should be relatively easy. I had a new one installed in the SD, $65, and a couple of hours. Worked on from underneath, has to use a breaker bar and pipe extension. When I replaced the V belts on that car, I bent a ratchet wrench loosening one of the alt bolts.

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83 SD

84 CD