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95 M3 Electrical Problem

Discussion in 'E36 M3 (1995-1999)' started by Joe///M, Jun 2, 2008.

    Joe///M guest

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    The vehicle in question is a 1995 M3 with 89,000 + miles

    This past Friday I tried to start the engine but it sounded like the battery was very low when the key was turned. The tach freaked out and I could hear relays and whatnot clicking under the hood and what sounded like the fuel pump stumbling on and off and the starter didn't operate. Thinking it needed a jump I hooked it up and tried it again and the same thing happened but after a second turn of the key it started up and drove normally to the destination. About 3 hours later it started up without incident and got home fine. Yesterday I started it up, proceeded to back out of the driveway and it quit, tried to restart it and the problem came back. Now when the key is put into the run position the original problem occurs. After several attempts of turning the key to the start position everything finally appeared normal but the starter turns the engine but there is a no start condition as if there is no spark. If the key is put into the start position the malfunction happens for about 10 seconds then stops but no start. During this time I was able to quickly get under the hood to find the o2 sensor heater relay and a vacuum actuator (not sure what it's "name" is) under the throttle body were the sources of the noise. Since I heard what sounded like the fuel pump I jumped the connection and the pump seems to be fine, I could hear it working and fuel flowing through the rail. At this time I tried to start it up but again no start. I also opened the cover where the ECU lives to see if it had gotten wet since I had washed the car Friday afternoon and it was bone dry. I have driven in the rain recently and on numerous occasions and had even pressure washed the engine compartment in the past without any problems. Any help in figuring out what the problem could be would be appreciated.

    Thanks
    Joe ///M
    • Member

    EuroWerkz1

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    Joe,

    You may have a problem I have seen twice in the last year both on E36 BMW's. A loose battery cable or ground cable connection or missing or broken ground strap at one of various locations. Check where the battery cable comes from the rear of the car to the jumping point in the engine compartment, check the condition off all cables, and more importantly ground straps around the engine compartment area. Don't assume anything is tight and making a good connection, check. You may be getting intermittent 12Vpower to the starter an other areas of the electrical system but the DME is shielded from power spikes that may occur so it need a proper voltage and amperage to function at all. As a last resort if none of the above bear fruit, have you battery load tested

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