Grounding issue, intermittent cranking

[Pursuit]

I have a starting issue, starter intermittently cuts out whilst cranking but does eventually start (crank - stall - hold key in start position - crank - stall - hold key in start position - crank - start).

Searching on forums, I tried grounding the motor to the chassis using jumper cables and problem was solved. Starts first crank. Jumper cable connected, first time start... disconnect jumper cable and the problem comes back. So somewhere there is a grounding or shorting issue.

The motor to chassis ground was toast, insulation completely degraded and wiring corroded so I replaced that with no change in starting problem.

Took off all the grounds I could find (battery, motor, fuse box and coil pack) and cleaned and reconnected. No change in starting problem.

I'm tempted to just add a few grounding straps and call it done but am worried that I might be masking a problem that may be damaging components.

Questions:

1. Am I missing any grounds?

2. Any thoughts on damage I could be doing by adding grounds?

3. Anyone else come across this?

[Platanos]

Is this a new starter install, or your old starter?

[Pursuit]

Old starter.

[J!m]

I would think the chassis/motor mount cable should have fixed it.

Make sure the connections are clean and tight. You could also add some copper never-seize to keep it from corroding in the future as well.

It should not be a problem to add another ground lead; however it should not be necessary either...

[Pursuit]

Originally Posted by J!m

I would think the chassis/motor mount cable should have fixed it.

Make sure the connections are clean and tight. You could also add some copper never-seize to keep it from corroding in the future as well.

It should not be a problem to add another ground lead; however it should not be necessary either...

I'm confused as well, all my grounds look good but the additional ground from the jumper cable clearly fixes the problem. Very frustrating.

[Philly]

Are you sure the starter is good?
when it "stalls" as you say, do you mean just quits entirely? or just stops "grabbing" but still spins?

I have some suggestions but im not entirely sure i understand your original post.


EDIT : i see your post above, so you did solve it with an additional ground?

If so, this is familiar to a problem I had with mine, I had it in the shop for a starter install and my mechanic installed the new starter and put the multimeter to my battery and it was showing lower voltage than it should have been, so he added another one to my negative battery terminal (still have it on til this day) and found better results.
A few months pass, my car dies and I found out my DME was slowly getting wet and/or moist, as some things are grounded within the DME itself, its probable.

[Pursuit]

Yes, the starter stops entirely... no spinning or partial engagement.

Grounding the motor to the chassis with the jumper cable solves the problem. It also makes the car idle much smoother. So I'm afraid there may be a short somewhere that is being overridden by the additional ground.

I checked the DME initially and was unable to see any signs of moisture, but am still suspicious as the hood cowling was entirely dry rotted to pieces and perhaps was allowing excess runoff.

[cooljess76]

Mine did the same thing. Had me confused for months. I kept killing batteries, it would take about 3 months for one to die. After three dead Diehards and 3 rebuilt alternators that all bench tested good, I was at my wits end. Basically I was in the same boat as you. I was ready to start grounding everything to everything. I was getting a fluctuation between 10-11v at the back of the alternator and across the battery terminals. I knew I should have been getting around 14v. Then one day, I was replacing my radiator when I decided to go ahead and degrease the front of the motor since I had the fan and radiator removed. I decided to remove the belts for better access at which time I accidentally snapped the A/C compressor bracket. Upon removing the A/C compressor bracket, I noticed the main engine ground. It attaches to the passenger side frame rail(chassis) and the passenger side motor mount arm. There wasn't much corrosion, but I noticed a lot of pitting on the cable end where it connected to the chassis. My only explanation was that it had a poor contact and would build up enough energy to create an arc and jump across the cable end to the chassis. This explained why I was getting a fluctuation in voltage and charging system failure. As soon as i got the car back together, I cleaned the mating surfaces on the motor mount arm and the chassis frame rail, and replaced the cable. Fired it up and checked the alternator with a multimeter. BINGO 14v!!!

If jumping the engine to the chassis corrects the problem, then your main engine ground is certainly the culprit. I recommend scrubbing the sh!t out of the cable and both mating surfaces with a stainless steel wire brush or lightly hitting them with a grinder(just make sure to leave the mating surface as flush as possible to maximize contact). You should also check continuity through the cable itself. It may have a corroded or broken segment under the insulation that you can't see. They sell heavy gauge grounding cables in the battery section at your local auto parts store, you don't need to special order the BMW part.