I had the air intake manifold off of my '86 190d 2.5 today to fix the rotten vacuum line going into the stop diaphragm that was preventing my engine from shutting off. After fixing the vacuum line and before putting the air intake back on, I started the engine and turned it off--sure enough, the fix had worked and the engine shut down properly, without me having to push the stop lever, like I've been doing everywhere I've driven for the past week. I was feeling fairly good--I'll I'd have to do was put the intake back on and I'd be done-right?.....

I got the intake back on with only a few stubborn bolts, and everything else back together, put the tools away and thought I was done.

I decided to test it one more time. Strangely, when I turned the key in the ignition, the light for the glow plugs in the instrument cluster didn't light up. The engine didn't start.

Somehow I've killed the circuit to my glow plugs. My only guess is it has something to do with the wiring harness that goes from the relay out to the plugs, because this is the only piece of the glow plug system near where I was working.

How do you test this thing--any ideas?