GM-GMC: Stumped, gmc sierra, ground 0

Question
I have a 1995 GMC sierra 2500 6.2 Diesel. I shut the truck off one night with no symptoms of any problems and the next day it wouldn't fire. It turns over no problem but it won't even struggle to start. I would think it isn't getting any fuel but having had no prior symptoms of anything being wrong I am not sure where to even start. I am caught between thinking it is electrical sensor of some kind or a fuel pump but I think the fuel pumps are mechanical leaving it to be some kind of fuel pump sensor or something like this. Where do I start? I did check the fuel filter at the engine and it was full of fuel and was clean. Can you help?

Answer
Steve,

Yes, I can help.

The injection pump is mechanical (with failure-prone electronics) on your engine, which should be a 6.5 L unless somebody changed it out for an earlier engine.  The electronics do not usually prevent the engine from starting but usually cause it to stall when hot.

The fuel transfer, or lift, pump is electrical and also prone to failure.  But first things first.

Do you see a glow plug or "Wait to Start" light?  If so, is it staying on for the normal amount of time?  If not, you have a glow plug and/or controller problem.  If the light seems normal, you may have some bad glow plugs.  Those are best checked with an ohmmeter set to its lowest scale.  Remove each connector at the glow plug and check the resistance reading by putting one lead on the spade lug of the glow plug and the other to a good engine ground.  0.8 to 1.2 Ohms is normal.  Anything over about twice that is bad.  You can use a test light, but it may light on glow plugs that are not burned out yet have too high a resistance to heat properly.

Let me know what you find and we will go from there.