The life of a glow plug.

[Am General]

What's the life expectancy of a glow plug? And what contributes to it's failure? My 01 TD with 48K miles starts rough in the cold. Plug it in it's good to go. So I think obviously I need more heat. Shouldn't my glow plug controller sense a bad plug and let me know? Isn't that a feature of the newer solid state glow plug controller? Could my plugs already need replacement, or could the connectors just need cleaning? Thanks for the help. My truck starts a litte rough at 33 degrees. I cant imagine when it's 10 below this winter if I don't get this squared away.

[BobND]

I know nothing about your Hummer, but against all odds, my old '94 6.5 TD is still starting very well on it's original 9G glow plugs @ 180,000 miles.

Generally GP's don't get weak, they either work, or fail completely. I don't know how the controller on your Hummer handles burned out GP's, but on the older 6.5's, when a GP or two failed, the length of the GP cycle decreased, so it was a double hit... total lack of preheat to a cylinder or two, and shortened preheat time for the remaining cylinders.

Check all your glow plugs. Get a 12-Volt test light.

Connect the ground clip to the positive battery post. With the glow plugs disconnected, touch the probe of the test light to each GP terminal, one at a time. The test light should light. Obviously, is a GP is "OPEN" the light will not light.

(I use an ammeter instead of the test light, and that way, can actually see what each GP is drawing, and verify that they are all drawing about the same current.)