I have a 1985 300TDT. It was running just fine until a few weeks ago when the pre glow light didn't come on. It started a few times, then went dead. I replaced the battery and it started a few times ( the pre glow light still didn't come on). The alternator checked out good. I went to start it the next morning and it didn't start. I checked the continuity in the glow plugs like it says in the manual. I've read some things on this site and they said they should read 0.5 to 0.9 ohms. I'm getting pretty close to zero! The Haynes manual doesn't state any values, rather they say that if you get an infinite reading then they are bad and must be replaced. Is it a possibility that the pre glow timer relay is bad? Can you test it to see if it's bad. The car turns over and sounds like it want to start.