7.3 flow plug relay issue

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Dec 14, 2024 | 03:01 PM

cuttn4fun

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Mountain Pass

Joined: Apr 2012

Posts: 142

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From: Nashville TN

7.3 flow plug relay issue

I just replaced my gpr with the ultimate one from diesel orings. I cannot get it to turn on. I have good voltage on the constant hot. The two small termials show voltage. 1 has 12.5v the opposite side one drops to 10.8ish key on. I tried to ground the orange wire and when it's grounded the gpr does turn on and stay on even after removal of the jumper wire. After it does power up even after the 2min mark it stays on continuous until I power the key off. Upon turning key back on gpr does not turn on until the jumper is placed on it again. This is in 30ish temps and cold engine so the gpr should definitely be wanting to power up.
I have the led light to show when gpr is on. It's connected to the big wire that powers glo plugs.
Any advice or insight? thanks in advance.

Edit.
This is a 2003 f250 with the 7.3 diesel. I have had this truck for about 12 or 13 years and glow plugs were changed 6 years ago. Never been an issue until last year. I figured bad replay but just kept plugging truck up to get it to start.

Dec 14, 2024 | 05:36 PM

Wes444

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Joined: May 2017

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From: Muskogee, Ok

Not sure about that brand of relay. The PCM grounds the small lug to activate the glow plugs. Voltage on it is bad for the PCM.

I use the Trombetta one after replacing the Motorcraft every 5-6 years

Dec 14, 2024 | 05:57 PM

tjc transport

i ain't rite

Joined: Mar 2005

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From: Marlboro Mental Hospital.

there will always be power to one of the small terminals with key on. the PCM grounds the glow plug relay. so if your relay is not getting ground signal, the glow plug circuit in your PCM is bad, or the wire going to the GPR is bad.

Dec 14, 2024 | 06:14 PM

cuttn4fun

Thread Starter

Mountain Pass

Joined: Apr 2012

Posts: 142

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From: Nashville TN

Quote:

Originally Posted by tjc transport

this is what I was thinking. Both small sides show voltage when key is on.. the one side shows 12v the other side 10ish volts. I may have to wire a push button into it to ground the one terminal.

Dec 14, 2024 | 06:31 PM

Pikachu

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Joined: Jun 2004

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From: Amarillo, TEXAS!

You did disconnect them to take voltage readings, right?

Dec 14, 2024 | 09:12 PM

cuttn4fun

Thread Starter

Mountain Pass

Joined: Apr 2012

Posts: 142

Likes: 2

From: Nashville TN

Quote:

Originally Posted by Pikachu

You did disconnect them to take voltage readings, right?

I did not. I checked the voltages on old one and new one with them connected to the gpr.

Dec 15, 2024 | 07:05 AM

Pikachu

Lead Driver

Joined: Jun 2004

Posts: 6,317

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From: Amarillo, TEXAS!

That's why you're seeing voltage on both of the small wires. The 12v constant wire is just feeding voltage through the relay coil. Disconnect the small wires, connect your meter probes to them and see if there's voltage there at key on.