Have a new to me 2000 excursion that won't start cold. Tested all the glow plugs at the harness and all are .7 to .9 ohms. With the key off glow plug relay has 12v on the supply side, .7V on the small terminal on Radiator side, .7V on small terminal on back side, and 0V on the large terminal for the glow plugs. KOEO 12V on supply side, 12V on the small terminal on Radiator side, 12V on small terminal on back side, and 0V on the large terminal for the glow plugs. Tried a new relay and same readings. Removed ground trigger wire from small terminal on back side of the GPR KOEO and grounded the terminal. Relay clicked and measured 10.5V on large terminal for glow plugs while supply side maintained 12V. Can one of you give me some direction? I have an 06' 6.0 and know that motor pretty well but new to the 7.3.
Thank you

 

The GPR is activated with a ground to the PCM when the PCM calls for glow plugs to activate. Oh, wait a minute...doesn't your Ex have a glow plug control module? (GPCM)? You might be checking your AIH relay.

 

 

These 7.3L engines like 5W-40 oil in the winter in a big way, and the 15W-40 has been known to prevent cold starts on older injectors.

 

Is this a recurring problem? Always have cold start issues or just suddenly wouldn't start? If injector wear is the cause you should have experienced cold starting/running problems for a while, if it's always been good and suddenly won't start it's not injector wear. Knowing these things will rule out injectors and help get on the path to finding the problem. Also verify that the THEFT light goes out when the key is turned on, if it's flashing there's a PATS problem causing the no start.

 

Some early 2000 Excursions have a GPR. I don't know what the cutoff is but you could have either. The first thing to look at is whether you have two GPR-looking things on top of the engine or one GPR-looking thing and a silver, finned box with two plugs coming out of the valley side of it. That's a GPCM and you first need to determine which setup you have.

+1 on the thinner oil in the winter. I use 5w40 year round.