Loose ground symptom

[COL 911]

1987 Carrera, stock 3.2, stranded me last Friday night - no start. No previous hot start issues. No click when turning key in ignition, no starter grinding noise, just humming or whirring noise from area of starter motor or solenoid that kept going. I disconnected negative battery cable and flat bedded her home - too dark, crowded parking lot, etc., preferred to diagnose at home.

Next day(s) I swapped out DME relay for new spare I carry, powered up - still had the noise from the starter motor or solenoid. Disconnected negative battery cable again. I checked, cleaned and re tightened all grounds using dielectric grease. Replaced gnarly, 8'' copper braid negative battery cable with 2 gauge, 15'' sheathed connector, which helped clean up look of wiring around battery. Cleaned and re tightened battery/post connections. Success! Started right up. I thought it sounded better, even my wife commented that it sounded better.

After thinking about it, though, I had similar noises and symptoms that resulted in new starter replacement about 5 years ago.

Could bad ground alone cause circuit to starter to 'stick' open, energizing starter solenoid, or do I have to consider and test for intermittent mechanical issue with starter and/or solenoid? Hoping the feedback here supports that bad ground-constantly open circuit could result in the reported symptoms so I don't have to go the starter removal test route. Thanks in advance.

[wwest]

Starter solenoid serves two purposes, first, "kicks" starter drive gear into engagement with flywheel gear teeth, then bypasses itself, supplying full battery power to starter motor.

Your solenoid is not kicking the drive gear into engagement.

[E Sully]

I would think a bad ground would have contributed to a solenoid problem. If the starter kept going, your humming or whiring noise, then it seems the contacts must be sticking. Might be time to consider rebuilding or replacing the starter. At least the grounds are good now, so next one will last longer.

[COL 911]

I don't think starter was engaging, or it would have made grinding noises against the flywheel, right? So, if loose ground didn't provide enough current to starter motor, just enough to either spin it (but not engage flywheel) or constantly engage shaft of solenoid, then it's likely with grounds cleaned, there was enough current to properly engage starter w/ flywheel. Lack of current to starter/solenoid, not mechanical issues w/ starter/solenoid itself was cause of no start condition.

I'll keep my fingers crossed based on improved starting/running after cleaning all ground points. Thanks!

[sugarwood]

For future reference, would anyone here be willing to photograph all the ground points to check and tighten on a 3.2 engine?

[COL 911]

Sugarwood, do you have Bentley service manual for '84-'89 models? Pg. 971-3, list and diagrams all grounds, photos throughout other sections. Couldn't manage without it...