No Start / No Crank

[4tDX]

So, I've been troubleshooting a no start/no crank issue all this weekend on my MT 1987 325i and I'm stumped. I've read novels worth of forum post looking for things to test, but as I said, I've run out of ideas.

I had no history of start issues before this. I had not performed any work on the car before this failure.

Things I've Tested:

1. Battery
2. Original Starter and known working starter (tested both starters out of the car and they both function properly).
3. Starter signal wire receives 12V
4. Crankshaft Position Sensor
5. Fuel Pump
6. Relays
7. Fuses
8. ECU connector - passed all continuity, voltage, and ground tests

Also, every electronic in the car appears to function properly when the key is in the ON position: windows, radio, lights, etc.

There is no dimming of the lights when I turn the ignition to the START position.

I've also run the ignition switch test in the Bentley Manual. Couple question about the Ignition Switch test that I've been unable to get an answer to, is... (1) When I performed the "Start only" test between C1 & C there was continuity when I first begin turning the key, but once I reach the full START position there is no longer continuity. Is this how it normally functions or should it maintain continuity? I've been looking at my cars wiring diagram and I can't figure out what C1 and C are for. The wires are BROWN and BROWN w/ LIGHT BLUE STRIPE.
(2) The starter signal wire receives 12V when the key is in the ON & START positions. Should it only receive 12V in the START position or is this working as intended?


From Bentley Manual, pg. 520

[spdracrm3]

"Starter signal wire receives 12V" is this when connected to starter or dis-connected? need a minimum of 10.5 volts in start position at soleniod wire on starter when key is in crank position for bendix to engage...

whats the voltage at the large cable on starter when key is in start position?
if over 11.5 volts what happens if you jumper from large cable lug to solenoid wire terminal with a jumper wire?

how are your ground cables?

[4tDX]

Thanks for responding.

The signal wire was receiving 12V when disconnected. Just tested it while connected:
Ignition ON: 1.5V
Ignition START: 11.65V

The large cable/post sees:
Ignition ON: 12.0V
Ignition START: 12.2V

When I jump the starter it doesn't spool up. I can hear the relays activate and the idle control valve comes on (BTW: I have a two post starter, but I have a 4th wire on the starter that runs from the small post to a relay in the engine bay). When I took the starter out of the car and jumped it, it spooled right up... Does that indicate a grounding issue?

I've gone through the car and checked the grounds and cleaned the ones I thought looked questionable, but that doesn't mean I didn't miss something. I'll give it another go over.

[spdracrm3]

well 11.6 at the solenoid wire and 12.2 at the battery supply should be enough for something to happen especially if it works when removed from the car. are you testing the solenoid control when your testing off the car or just jumpering the battery to the large lugs and hearing the motor spin. if so your not testing the solenoid/bendix which is basically a giant relay/switching the battery voltage to the windings of the motor while pushing bendix out to engage flywheel (run positive to the same lug as the battery cable attaches to and the neg cable to the starter body then jumper with a small wire from positive to the solenoid control terminal and the bendix should kick the gear out and the motor should spin if its working properly, be sure to hold on as it makes a lot of torque)

might have a ground issue , make sure there is a large diameter or braided cable running from frame rail to the block or oil pan usually on left side of motor low down. do a voltage drop on the ground side download your ETM an read the first few page for a description of that test

http://www.wedophones.com/BMWManualsLead.htm

[4tDX]

I believe i was I was testing (not bypassing) the starter solenoid... Ground was hooked to the case. Power was hooked to the large lug on the solenoid and then I jumped power to the S terminal (terminal 50 in the diagram?).



I've also installed a known working starter/solenoid in the car and still had no cranking.

The oil pan grounding cable is installed and looks in good conditions.

Still have not run any voltage drop test. I plan to do that tonight.

Keep forgetting to mention that the crankshaft is turning freely.

[4tDX]

So, I cleaned all the grounding locations in the engine bay: strut post, oil pan, and both locations on the left of the engine bay. I plugged in the battery and went to turn the key thinking that there was no way it was going to turn over... the car roared to life.

Moral of the story? Stay grounded... pun intended.

Thanks for the guidance spdracrm3.