Re: 1984 733 Motronic, Please Help, out of ideas! (archive)

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it appears as thought the problem with your car started after it had been used to jump start another vehicle. I wonder whether the jump starting procedure was done CORRECTLY. It is very possible to damage the motronic circuitry of your car by using to to jump start another car. All sorts of crazy things can happen depending on exactly which bit of the motronic an unintended spike damages. Suggest you substitute the entire motronic and see how you go. I am not an expert on E23s but I am learning and have a pretty solid background in electronics

We have a 1984 733, one family owned since new, approx 107,000 miles. Very original, very nice condition. I bought the car in damaged condition. Replaced fender, nose panel and had frame rail straightened.
Main relay on firewall was bad, replaced it and car ran well for about 12 months to Florida, Smokey Mountains & New Jersey (we live in North Carolina.)
Bought a parts car one weekend, had to jump it with the 733 about 3 times to get it running.

2 days later the 733 refused to start, car had been parked for about 20 minutes after a short run. Cranked, wouldn't start, left it overnight started immediately ran about 5 miles and died. wouldn't start. No fuel, pump not running, no fuel pressure. no ignition, no spark. Car cranks & all accessories like lights work OK. Have tried changing out parts, including relays, air flow meter, fuel pumps & filter, ignition coil. Tried jumping fuel pumps they run when jumped.
At Christmas, while I was on vacation, my son swapped out the air flow meter and the 733 cranked up. Ran for a few hundred miles then started acting up on the interstate at about 70 mph, hesitating and running rough. Just made it to the airport, had to push it into the parking space. 5 days later, cranked right up and ran for a few more days.
Yesterday, ran a couple of errands around town, Stopped at Wal Mart, started the car, ran for about 30 seconds, pulled out of the parking space and stopped dead.
Doesn't miss or run rough, just shuts down. Left it all night, wouldn't start, cranks, doesn't fire, no fuel pressure, no ignition.
I have spent time with BMW tech service advisors who have been very patient with me.
I've tried unplugging the air flow meter & plugging it back in. Ive tried disconnecting the battery and reconnecting and all of the other things mentioned above.

Only other thing I can think of mentioning is that the on- board computer has not worked since we have had the car also, the car has a strange problem with the instruments. The green turn signal lights on the display as well as the blue hi beam light cause the instruments to malfunction. The speedometer drops to zero and the temp gauge goes to max.
This happens when the car is running and doesn't seem to affect its performance.

I realize this is a long explanation but I thought anything here could be causing this hard to find problem.

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