I am the worried new owner and am pleased to have found this forum! Here are the symptoms of the car (I bought it at auction and didn't have a chance to drive it):

Loud knocking on startup,
Almost no power whatsoever,
Car crawls away from a stop and is noisy,
Battery seems to die if I use the car for a few minutes.

A search on the Net found a note posted by a mechanic that suggested these symptoms can be brought on by the introduction of gasoline into the fuel tank. None of the manuals I've got (Haynes and Chilton's) make it clear how you empty a fuel tank, short of running it down. Since the car has 1/2 a tank full and it runs rough, I'd rather not do that.

Is there a drain plug on the fuel tank? I can't find one from under the car. Would I do almost as well to siphon the fuel out? Should I just siphon a cupful and see if it seems like gas (I don't know what diesel should look/smell like)?

Following suggestions on this forum, I'm going to change the air and fuel filters (and pump up the fuel), change the oil (using Delo 400 15w40) and coolant. Testing the glowplugs and injectors are beyond my humble talents, but I have a feeling that someday I'll be doing these things, too.

Thanks for any help and advice you can give!