I have a 2000 7.3 not cali. I replaced my gpr with the stancor or white rogers relay. With key off I have 12v on one large post and 0 on the other. Both little posts 0 also. With key on 12v on one big and on both little but not on the other big post. Is it possible my new relay is faulty or am I missing something. Since its not cold today I was able to start with no problem and when I tested the glowplug side of the relay again I get 24v

 

12v on one big post is normal since it's hooked directly to the battery. 12v on the two little posts with the key on is fine also. One of the little posts switches to a ground to activate the relay (ground signal controlled by the pcm) and that should send 12v out the other big post to energize the glow plugs.

Testing while warm can be hit or miss. Unplug your EOT (engine oil temp) sensor and that should cause the glow plugs to energize for two minutes after the key is turned on. That should give you time to test to see if it's all working.

 

Thanks ill try that...i thought by having the 12v on the small posts that would close the switch and send power to the plug side of the relay

 

Relays work by having current flow through the coil, developing an electro-magnet, which causes something to move inside toward the magnet.

That requires having +12 volts on one end of the coil, and GROUND on the other side.

There is no current flow, and thus no magnetism, if the voltage is the same on both ends of the coil.

Pop

 

Here is a diagram I made up to show the GPR System. You can see the ground is internal to the PCM. As Chris said, disconnect the Oil Temp Sensor on the HPOP Reservoir to trick the PCM into grounding the GPR out. You can also manually ground it out with a short jumper from the post to a known ground. Watch the video below where I do that. You will at least be able to check the relay's operation that way.