As for the late 617 engine, if you have only one glow plug is bad, you should still start the car at room temperature but the light will not be on. The smoke from the tailpipe is the raw diesel fuel.
If glow light starts not to work lately and you cannot start the car right after discovering the malfunction light, your problem is likely the 80A fuse or the +12V to the relay box.
If your light has not been working for a while and only now you cannot start the car, it is likely that 2 or more plugs, but not all plugs, go bad.
[Edited by be459 on 07-09-2001 at 02:29 AM]