I was away on a sailing trip a few weeks ago, and my wife had trouble starting the for a couple days, then one cool moring it wouldn't start at all. Took it to the garage and they replaced all 4 glow plugs, which were burnt down to the "nub" (my word). Unbeknownst to them, I had replaced all 4 glow plugs in the fall!

Now, only a month or so later, the car is smoky and rough on startup... I suspect the damn glow plugs are burnt again. What could cause this?

I've hooked up a test light to the GP buss bar, and the light goes out after 10-15 seconds or so. I've also tested it when hot to see if teh glow plugs are coming on when I hot-strat the car... they aren't.

Any ideas?

interseting... I'm going to hook one of those lights up.

Leaky injectors, eh? Maybe I'll run a dose of Diesel Purge.

Took it to the garage and they replaced all 4 glow plugs, which were burnt down to the "nub" (my word).

I agree that this problem points to injector problems.  I'll bet if you have your injectors tested, they will show problems either with bad spray pattern or leakage, like fatmobile suggests.  Having new nozzles installed in them (getting them rebuilt) should restore them to new condition and stop your glow plug erosion problem.

Take it to a diesel shop and have them tested for spray pattern, drip and breaking pressure.

Precision pump and injector service corp in Bellevue.  Jay and Bill are the father/son owners and are both great guys and they do outstanding work and are very patient, helpful and friendly too.  Tell 'em I sent ya.