Well I started out here with a 7.3 and moved through the forums up to the 6.7,
back here now I bought another 7.3 for a work truck.
Ive forgot lots of things about the 7.3?

How do you check the glow plug controller to see if its glow plugs or the controller?

 

Turn the key on when the engine is cold and check for power on the right side of the GPR. If you have a GPCM I don't know what you do.

 

do you have a GPR or a GPCM?

 

A GPCM is supposed to give codes if there is a problem. You can ohm out the connectors to see if the glow plugs are good. At the 9 pin connector on the valve cover check the two pins on each end to ground.

Someone posted a diagram of the connectors at the GPCM not to long ago. Might do a little searching.

 

Here is a link with some info. Post number 2 has what you're looking for to test the glow plugs. Testing through the valve cover harness won't guarantee that the plug is the problem, but it will definitively tell you if it isn't the problem. If all of the readings are within spec, then you know that the valve cover gasket, under valve cover harness, and glow plug are all good. If you get a bad reading, any of those 3 could be bad, or it could have come unplugged under the valve cover (in which case see the 50 cent mod). If all the readings are within spec there is no reason to take off the valve cover.

https://www.ford-trucks.com/forums/1059878-2003-f250-7-3l-glow-plug-testing.html

are you having symptoms of anything or just wanting to check them?

as far as testing the relay goes, use a volt meter between battery ground and the switched positive on the GPR (the side that goes to the plugs) I use leads with alligator clamps and connect it with the key off, then position the meter somewhere I can see it when I turn the key. When you turn the key on you should read battery voltage on the meter. If you dont:
-connect meter to battery negative and the small positive trigger wire on the relay.
. - If battery voltage is present, check the resistance on the negative wire for the GPR to ground to make sure it has good contact. If good, replace the relay
- If no battery voltage is present, test for a fault in the trigger wire. If you get to this problem, let us know and we can get you wiring diagrams.

kinda long post, but hopefully this gets you going.

 

I have power going through the relay with the key on and off?

 

I think you may be checking the wrong side of it. One side should be hot all the time, the other should be on when the key is turned on and the PCM calls for glow plugs.

 

Exactly what are you measuring? The GPR has four lugs, two large and two small. One large is fed directly off of the battery and is hot all the time, the front small one is hot when key is on, the other large one is hot when GPR is activated and the small one to the rear is grounded by the PCM when glow plugs are called for. If youre GPR was activated all the time your batteries would probably die overnight.

 

I turned key on, both large lugs had power, one clicked off and went out after a few seconds.
So I would say the controller is working? Opinions please?

 

Use a digital volt meter. Measure voltage across the two large posts on the glow plugs relay. With the key off it should read battery voltage. Have someone turn the key to on. The relay should activate and the voltage should drop to less than 2 volts. If you're reading is higher than 2 volts, the contacts inside the relay are bad and it needs to be replaced.

Then check ohms at the nine pin connector at the valve covers. The pins are as follows.
GGIICIIGG
G=glow plugs
I=injector
C=injector common
Check glow plugs to ground. It should be less than 2 ohms. An open reading indicates a bad glow plugs or wiring connector under the valve cover.