Hey all, so I've had this 1985 318i m10b18 for a few years but never had the time to get it running. Its always just died intermittently while driving. When it does its as if it loses power slowly and steadily until it cuts out. Ive gone through almost everything related to the L-jet system and nothing really works. I finally decided to try the throttle position sensor, and when I tested its connector for voltage it gave me some weird numbers. according to the bentley manual "With the ignition on, there should be at least 5 volts VDC between the center terminal and either of the outer terminals of the switch harness connector." when measuring mine, I got 12v between one outer terminal and the middle, and 0v between the other terminal and the center. Because the voltage isn't correct on that connector, I tested the ECU connector according to the bentley manual for power and it doesn't seem to be getting all the power it needs. according to the manual, terminals 13 (ground) and 9 should read 12v when tested with a multimeter while the engine is cranking. after dozens of tests I consistently only get a reading of 0.9v. I also tested pins 13 and 4 (wire from starter solenoid) for 12v and got 0.9v. So I'm sort of lost on what to do next, I really have no idea what I'm doing with electrical but I'm trying to learn.
My question is does anyone know what could be affecting the voltage to the ECU? My guess was that maybe there's a relay that controls battery power to the ECU that could be going bad? or some other electrical component between the ECU and the battery that has gone bad? My 318i has three relays outside the fuse box which are the fuel pump relay, the vacuum advance relay, and the idle speed stabilization relay according to the manual.
I also had a parasitic drain this whole time, so I hooked up a multimeter in sequence with the negative battery terminal and cable and got a reading of .09 amps being drawn. so i went through pulling and replacing each fuse, turns out the drain was the gauge cluster, which runs through fuse 21. so when I have the blue connector on the back of the cluster removed there is 0 amps being drawn. but shouldnt there be a little bit of draw? to keep the clocks memory or something like that? this may sound really stupid but i was wondering if maybe the ecu problem is related to the cluster, like if the cluster is bad then the ecu wont get the right voltage. I dont know. I could really use some help, im depending on this car to make it out west and get an apprenticeship in race fabrication, so Im pretty stressed about it.
My question is does anyone know what could be affecting the voltage to the ECU? My guess was that maybe there's a relay that controls battery power to the ECU that could be going bad? or some other electrical component between the ECU and the battery that has gone bad? My 318i has three relays outside the fuse box which are the fuel pump relay, the vacuum advance relay, and the idle speed stabilization relay according to the manual.
I also had a parasitic drain this whole time, so I hooked up a multimeter in sequence with the negative battery terminal and cable and got a reading of .09 amps being drawn. so i went through pulling and replacing each fuse, turns out the drain was the gauge cluster, which runs through fuse 21. so when I have the blue connector on the back of the cluster removed there is 0 amps being drawn. but shouldnt there be a little bit of draw? to keep the clocks memory or something like that? this may sound really stupid but i was wondering if maybe the ecu problem is related to the cluster, like if the cluster is bad then the ecu wont get the right voltage. I dont know. I could really use some help, im depending on this car to make it out west and get an apprenticeship in race fabrication, so Im pretty stressed about it.
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