History of the problem.

Car was showing no issues. Parked the vehicle and 30 min later would not start (no crank). Battery was tested at auto parts store. Tested good.


New aftermarket starter was ordered. Tested good at store. Also tested with the battery on bench. Tested good. Starter was installed. Clicks but no crank. Pulled the starter again.

Also pulled the starter relay and tested it with a multimeter. Resistances tested good. I did not power to relay on the bench. However I moved to my next test which was to reinstall the relay and hook up the appropriate electrical contacts from the car to the starter (but not install it in the motor). I used this as a test of the relay and ignition switch's ability to activate the starter, and the starter's ability to extend the shaft and turn. All 3 tested good as the starter was appropriately activated on this circuit.

I reinstalled the starter. Cranked. Again just clicking. No crank.

I decided to do a voltage drop test. Positive side circuit tested good.

Negative side voltage drop from (-) cable to engine and from (-) cable to starter housing both showed .8v drop during cranking. I'm taking .5v or less as normal. Is .8v a normal drop on a Mini or is there something wrong with the wiring/ground?

I cleaned/sanded contacts to the front passgenger side ground and retested the negative drop but no change. I'm not sure where to go from here. Was unable to visually locate the other engine-to-body ground locations.

I also have a few other concerns overall:

1. The replacement starter I have is aftermarket. As stated above it has tested good multiple times on the bench and when hooked up to the car/starter circuit).. however is it possible that it is actually defective? I also notice the gear on the replacement starter is slightly smaller diameter than the original mini starter. The starter only clicks (shaft protrusion) when installed into the motor.
2. Could the battery be bad even though it tests good? It sits at around 12.2V. It powers the starter fine when the starter is bench tested.
3. Could a bad battery also explain the voltage drop test results? Remember the postive side test shows normal across the board.

 

At 12.2V the battery is only at 50% charge. This and the symptoms strongly suggest the battery is the culprit.

 

Thank you for the reply. I just returned from the auto parts store. Was there with the intent to purchase a battery as I was coming to the same conclusion, and am bit desperate to fix the issue. I have another vehicle to drive obviously. I'm simply of mulling over the problem (its been weeks) and poking around the engine bay.

I had the old battery with me for the core exchange fee.. but and they tested the battery for me and told me it was reading 12.6v and the tester said the battery is healthy.

Would love to see if there are other suggestions on how to proceed. Otherwise I'll return to the parts store in the next few days to grab a battery, despite what their tester says.

 

With everything you've done so far, I'd get that DVM back out and start resistance checking the wiring harnesses. Primarily regarding the alternator and starter. I suspect that you've got a short to ground somewhere (or an open) and it's not getting current to the starter relay in order for it to trigger properly.