1987 (12/86) 325is starter / relay issue

[1987e30]

Hi. I have been reading these forums for a few months, and am new to the BMW world - making progress with the help of that 101 projects book!

I have an almost junkyard worthy e30 that used to run (barely) but now turning the key does nothing. I have tried jumping the legs on the starter (ignition switch and battery), but no starting. I have 12 volts from battery wire , but 0.2 volts at small terminal when starting (0 otherwise). Interestingly, the blower motor comes on when connecting the starter terminals - even with no key! I think jumping the terminals activates the k7 and k5 relays from the wires that normally ground it (going through relay coil in opposite direction of flow). Fuse 20 has 12v when jumping the terminals. Blower resistors may be out as it only works on high - but that's another story.

Turning the key to run does not give power to the blower motor. Only jumping the terminals or jumping pins 11 to 14 on diagnostic connector.

It seems the ignition switch is malfunctioning, but other functions (clock, interior lights for ac control, and overhead computer lights) come on only in run...

It's an auto, so a start relay is a possibility, but doesn't explain everything. If stuck open, voltage will never get to starter, but fuse 20 should energize from k7. Currently, only jumping starter terminals energizes it. Range switch could be bad as well. Shifter glides from park to 1 without firmly stopping at any in between.

K7 and k5 seem to work when starter terminals are jumped, so they should be ok.

The starter is most likely bad, but I'm not getting 12v at pin 50 on starter anyway , so there must be another problem.

I need to check power to fuse 10 tomorrow. If it has power in run, fuse 20 should.

Any suggestions? I'm a mechanical guy - new to electrical troubleshooting. Feel free to dispute any of my assumptions. Any suggestions welcome!

[1987e30]

So everything is wired correctly. Fuse 10 only gets 1.5v, and fuse 16, 17, 19, 20 see 12v when terminals are jumped. K5 and k7 are energizing from the back end, and the blower motor (fuse 20) is being powered. If fuse 10 Saw 12v, the relay would be deenergized.

I'm not concerned with the blower motor as it is explained by fuse 20 getting power. I don't understand how fuse 10 would not see 10 volts?

Once i get fuse 10 understood, I can check start relay, range switch, and ignition switch. Ignition switch seems ok because certain interior lights (overhead diagnostics) come on in "run".

If it helps, fuse 3 saw 0.05v, and 12 saw 0.4v when terminals were jumped. No key in ignition for any of these tests.

Other fuses to see power (12v) were 21-28, but they all run lights that will work with no key, so that was normal.

[markdas]

Yikes, E30's and electrical faults go hand in hand!

Its odd you have some power, but not much in certain places!

I quickly read your post, so forgive me if I ask something you have already done!

I guess you have a confirmed good battery, with good terminals and connections at the battery posts, now also check the earth wire connection to the car chasis.

Is you batter in the truck or in the engine bay? Either way, check the positive heavy wire and you will find a lumr in the insulation, there is a big heavy fuse in there, check it for corrosion etc.

Haveyou done any major changes in terms of engine or wiring loom, these cars have specific years where engine looms and main harnesses are not interchangeable.

Check all the other earths in the engine bay, on on the sump to chasis, and there is usually one on the back of the block to bulkhead.

You can also try turning the key into position 1 and disconnecting the battery for 20 mins, this used to solve our immobiliser issues a while ago!

Check if you have any 12v supply at the coil, fuel pump relay and main relay, try linking out the fuel pump with a wire and confirm its priming the system.

Have you removed or changed the ECU at any time?