The car in question: my girlfriend's '79 240D automatic.

It's been having issues starting since we've gotten it. I determined it was a number of issues, including air getting into the fuel system via a bad IP seal to injector hardline #4 (still have to fix that) and a starter/solenoid combo going bad. It's the latter that's giving me real issues.

I got a rebuilt Bosch turbo starter from -insertobvoiscompanyhereinBellinghamWA- and spent a good 5, 6 hours finagling the old one out and getting this bad boy in. Near the end, I was having difficulty wiring-up the new starter, mostly not remembering which wires go where. Saw this by arching and bad sparking when touching the battery terminals with the connectors, meaning there was obvious load on the system. Called my friend over who also is a dieselhead to help me, and we finally got it hooked up and started with no issue (other than the air leak making the turnover difficult).

It went all south last night. I drove her car to college to stretch its legs. Started up fine at the house. Didn't even engage when I tried to start it after class a few hours later. Turn the key, wait for the glow light, turn to fire the starter... -click-. Hit the starter and solenoid a few times, kept trying. Nothing. Called AAA and they sent out a local tow truck. Told him my issue, so we both started messing with it. Here's what gets me confused: He took out a metal rod and when he touched the positive terminal of the starter and the support bar for the air cleaner housing, it started right up. Now, I now you can normally bypass the switch by jumping the connection between the positive starter terminal and the small terminal for the ignition switch. But he just grounded the system. I thought the starter grounded itself to the block...?

So, tl;dr version: Is the starter not grounded properly?

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- 1979 W123 240D 4-speed, 390k miles