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Old 03-18-2014, 11:07 AM Rookie

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Glow Plug Relay

I am having trouble getting my 79 Bronco with a 95 Powerstroke Turbo Diesel started. I am thinking it is the glow plug relay, so I tested it today.

Here are my results:

You can see which post I am testing in the picture, with the voltage I am getting.

Please keep in mind that my batteries were not completely charged at the time of the tests. That would explain the 10.62V at the hot post.

My batteries could probably be replaced, but I do not think that will solve my problem, as the truck turns over at a good rate, it just will not fire.

Is the glow plug relay my problem?

Thanks for any help!
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Old 03-18-2014, 12:35 PM
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The key is the DIFFERENCE between the voltages at the two big terminals. It's almost 0.7V, which is well above the 0.3V threshold. Means you have a lot of voltage loss across the contacts of the relay, and indeed, it should be replaced.

Quick confirmation test - jumper the big terminals with a jumper cable, or just run a jumper cable from the battery + to the "not always hot" big terminal (the 9.94 one). Connect for 10-15 seconds, then try to start it. If that helps, confirms failing relay.
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Old 03-18-2014, 02:46 PM Rookie

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Thank you for the response.

I ran a jumper cable from the not constant post to the + battery terminal, and the truck seemed like it could have wanted to fire, but I need to charge up my batteries again and try.

I will order a new relay tonight and swap that out and see if it remedies the problem.

I'm going to try to win this auction:

7 3 Powerstroke Glow Plug Relay | eBay

P/N DY-861. I read there are DY-860 and DY-861 should work just the same for my 95 Powerstroke.
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Old 03-27-2014, 02:15 PM Fanatic

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You definitely have a failing relay with that kind of voltage drop.

I wouldn't bother trying to replace it with a stock one. It will just fail again, probably at an inconvenient time.

Welcome to guzzle's White-Rodgers (Stancor) GPR replacement Mod Web Page covers how to replace it with the Stancor relay that should last pretty much forever.
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