Ok guys, I'm at a loss right now with a glow plug issue. Even at a balmmy 20* the truck takes a lot of turning over, something like 30 seconds with a rest of 30 seconds followed by starting somewhere in the next 30 seconds of turning over. It isn't a fuel issue. The ECM is cycling the GP like they should, there is 12V going to the GP for the 12 seconds on and cycling on and off like it should. Last time I did a compression check it wasn't that long ago and it was where it always has been, a little low but within limits. I know there will be times when I can't plug it it at -20 and no way it will start like this. Am I just missing something simple? It starts warm (or even first start in the morning above 35*) just fine with no issues. It had actually started this game last year and it wasn't a gradual issue, fine one day and not the next.
Glow plug issue
- Thread starter adeso
- Start date
Have you actually checked the glow plugs? They can be receiving power but not doing anything. What is the amp draw when the glow plugs are cycled on? Federal LB7 engines have no diagnostics if glow plugs fail. I had 7 of mine fail over the summer last year and was having the same exact same starting problem.
You couldn't be more right, had the same exact thing happen to me last winter. Ohm tested them had had several bad ones.
Take a test light, put your clip on the positive terminal, probe the end of the glowplug and see if the tester lights up...
That works but isn't accurate enough to determine a bad one, using an ohmmeter would be better, I had 3 that would pass the testlight test but still ohm'd out as failing according to GM.
Do you get lots of white smoke when it does start? If so I would suspect a glow plug issue. Common LB7 federal glow plug issues is the metal tie bar will burn through on the drivers side just in front of #8 glow plug. Or as others have stated, if just 1 glow plug is good, the ECM will not code. If you get no smoke during this extended cranking, then I would hook a scanner up and check your rail pressure while cranking and make sure your building up to at least 1500 during cranking.
Get a test light and make sure you are actually getting power to the glow plugs. Lots of white smoke means your getting fuel, so you need to get some heat in it. Just in front of the #8 glow plug is a common place to look to see if the metal tie bar is burned through.
The crazy thing is I had this same thing happen to me. I did not replace my glow plugs when I built my engine due to them being fairly new. Made it one year and bam; 7 burnt open and no start under 25°.