Good deal!!

 

Your high pressure oil pump could be weak. the truck has two pumps in it one for lubricating the hi side to fire the injectors. and you may have some injectors getting bad. they maybe firing less that 70%. I had this problem in my 96. And then again it could be something as small as a O ring in the fuel filter not sealing good.

 

I've done everything you suggested, changed the fuel filter, went through the fuel hedder with new o'rings, rechecked the glow plugs and by the way two of the new ones I put on it were bad I ohmed them all out and two of em only showed .001 ohms (AC Delco, go figure), re-replaced those two. I replaced the fuel tank relay and ran new rubber lines in place of the old plastic ones. Every little thing I did helped it a lot. It still turns over more than I would like it to, but it starts on it's own every time. Thanks guys.

 

Does anyone know how the heater functions on a 1991 7.3l? ....and will it cause starting problems?

 

the '91 doesn't have a heater, it has glow plugs. They work off of a timer and relay that are activated when you turn the keyswitch. When you turn on the switch, the wait to start light, just to the right of the steering column, should come on for about 10 seconds.
The relay itself is located at the back of the engine, just behind the air cleaner. You can check to see if you are getting voltage to the glow plugs themselves at the glow plugs. The glow plugs are located in the heads right close to the injectors, they each have a single wire going to them. Have someone turn on the keyswitch, and check for voltage with a test light or volt meter were the wires plug into the glowplugs. If you are getting 5-10 seconds of voltage to each of the glow plugs, you can check the plugs with a volt meter. Unplug the glowplugs and check the ohms between the part of the plug were the wire plugs onto, and the engine block. You should have little to no ohms of resistance, if there are more than about 0.10 ohms, I would replace the plugs.

 

I have a 97 7.3 that has a hard start when its cold. I know that it is in the glow system but im not sure if its plugs or the relay. The light (wait to start) is only on for about 3 sec. then shuts off. Is that week plug or the relay? Where is the relay located on a 97? Any help is greatly appreciated!