Question95 gmc 6.5 ltr. diesel. starts hard and wait to start light does not come on at all. Replaced theglow plug controller, did not help. could it be wait to start bulb is bad and i'm trying to start before glow plugs work or are the glow plugs bad?
AnswerIt could be the bulb, and you should check it.
However, at least on the driver's side, you can check the glow plugs more easily than replacing the bulb.
Get a volt-ohmmmeter and set it to its lowest resistance setting (often, the 2 Ohm setting). Remove each wire at the glow plug and test them separately. The resistance should be approximately 0.8 Ohms with the engine cold. Anything more than twice that reading indicates a bad glow plug.
If you have bad glow plugs on the driver's side, odds are the passenger side glow plugs are bad, too. If they need to be replaced, buy some self-limiting (also called positive temperature coefficient) glow plugs that resist burning out.
If one, or more, glow plugs seems stuck, send another request for instructions about that problem.
