So yesterday Iridium and I pulled his glow plugs, reamed the openings, installed new Bosch plugs, etc. It was a mix of preventative maintenance as well as an effort to correct a bit of a slow, stumbling start on his '84 300D.
In the process we pulled the injector hard lines. Turns out he also needs a new primer pump (he has the old style and while it's not leaking, it is also not pumping worth anything!). That all meant that he was going to have to do a bit of cranking to get his lines purged of air and the engine running.
Well about 5 seconds in to his first cranking attempt I yelled - STOP!
His positive battery cable had begun smoking
I'll save you the story of some of the investigation we did but we found that the clamp on the end of the battery cable at the battery was getting so hot it was melting the metal of the clamp. After letting the car sit a bit he tried to do one more short crank and --- nothing. Dead. No power. The battery cable had just bitten the dust.
It was easily fixed with a new positive cable. The auto parts store doesn't carry positive cables of any reasonable length in anything large than 4ga so he'll watch it and likely plan to make up some 2ga cables in the near future. We also replaced the ground with a 2ga cable while we were at it. Bottom line - problem solved, car started.
The investigation in to the cable itself showed bad internal corrosion, which lead to increased resistance and therefore heat! The picture doesn't quite do it justice - the inside of the cable was very discolored and overall nasty looking.
So the lesson here is that after 30+ years in operation even a simple cable can be considered a wear part. Inspect those cables as best you can, and replace them if necessary. Thankfully replacing the starter cable is fairly straightforward.
1) disconnect positive cable at the battery
2) under car, at upper front of the starter, un-do the 17mm bolt holding the positive cable in place
3) remove the phillips screw holding the smaller wire to the starter
4) Cut the wire tie holding the block heater wire to the stater wire harness (if applicable)
4) pull harness out through a grommet that holds it tight to the inner rear of the fender
5) cut end off of starter cable and pull it out of the harness wire sheath
6) put new cable in to sheath
7) reverse the process to reassemble