Glow plug Relay problem

[StrokedFirefighter]

I have started having problems with cold starts. Thought the Glow plugs needed to be replaced so replaced all 8 gp. Still having problems starting. The GPR has been checked and the relay will not ground to complete the circuit to send power to GP. Ive read problems with PCM could cause this and am trying to find a wiring diagram to chase the ground or somone to help me figure out the next step. The truck will start if plugged in but not start in 45*f weather conditions. Thanks for any helpful tips I have tried everything that I have previously read from many different threads however cannot pin-point exact problem.

[shiz big red]

Is your relay stock?

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[StrokedFirefighter]

No its the 2nd time I have had to change it I have tested the relay and can get it to work if I give it a Ground to close the loop. The truck has 160K miles and I changed the relay at 140K.

[shiz big red]

Sounds like a bad relay. Get the Stancor relay its able to take the load needed. Those stock relays and others like them can't handle the load and fail regularly. Also check all wires for damage just to be safe.

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[NoRalPh]

Here's what I would do,,,,, Disconnect both of the sm. terminals wires. With the key ON you should see 12v in one of them. Put that one back on the relay and just use a jumper to Ground the other sm. post that still has the wire off it.

Does the relay "throw"? If so, there is a problem with the PCM being able to supply Ground to the relay (PCM itself / wiring / bad sensor making the PCM think the engine doesn't need the GPs)

Does the relay NOT "throw"? If not, the relay is just Bad....

[StrokedFirefighter]

Ok Did the suggested ground to the smaller post on the relay that is supposed to ground out for the relay to work, and the RELAY Worked fine. So the PCM or some kind of wire issue seems to be the problem does anyone have a wire diagram to follow and make wire is entact and good all the way to the PCM.

[NoRalPh]

What year is your truck?

Always an important thing to include when asking for help....

[StrokedFirefighter]

Sorry Its a 2003 7.3L Automatic Trans

[NoRalPh]

You also might want to check the EOT (EngineOilTemp) sending unit. It's one of the main things the PCM relies on to know the GPs need to be activated.

[StrokedFirefighter]

Thanks I will check on that Tomorrow and appreciate the diagram that will help a lot with troubleshooting