93 F350 Glow Plug Relay Clicking

TheRagnarok · Jun 17, 2020

So I have a problem with my 93 F350 7.3 IDI.
Thought I heard a relay clicking constantly while the engine was running.
And the smell of melting plastic lead me to this....

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A well done glow plug relay.

Would a bad glow-plug cause the relay to constantly cycle?

The Gill Fish · Jun 17, 2020

Usually takes a few bad glow plugs to cause the relay to cycle continuously. Testing the glow plugs with a test light is fairly easy. If I remember correctly, just put your clamp on the positive terminal of the battery and try to ground your light through the top of the glow plug. There are many threads on that.

For replacement glow plugs, stick with the Motorcraft parts that were oem spec.

For replacement glow plug relays, go with motorcraft or the White Rogers model via classic diesel design. Avoid the cheap ones from NAPA. I’m told they are aluminum inside.

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DaveBen · Jun 18, 2020

I am going to disagree with The Gill Fish on glow plugs. USE ONLY Motorcraft or Beru glow plugs. All the others can swell as time goes by and are almost impossible to remove without removing the head(s). But it is YOUR truck, so use what ever you want.

The Gill Fish · Jun 18, 2020

Daveben is correct. Had a brain fart last night. Only Motorcraft glow plugs with the Beru Germany stamp on them. Part number ZD9 for the 7.3 engine. Here’s a good article that covers the topic:

https://www.dieselhub.com/maintenance/idi-glow-plugs.html

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TheRagnarok · Jun 18, 2020

Thanks guys, I replaced the relay from some IDI parts I have laying around and disconnected the white wire temporarily.
Truck still starts cold after about 15 seconds of cranking.....
I will jump on the glow plugs this weekend.

mblaney · Jun 18, 2020

Here is a "hack" I will highly recommend. Add an oil pressure switch to disable the GP controller once you have oil pressure. This has failed me once when starting - with no block heater (due to very remote location) and at -28 C... but this prevents your GP's from cycling after a firm start (i.e. oil pressure). I have noticed a significantly lower GP failure rate since adding this.

For the switch, any NC switch will do. They are cheap, save you a lot of wear on GP's. This would not fix your problem, but would totally eliminate the cycling symptom you have. You still need to fix whatever the underlying problem is.

Fredrickson · Jun 19, 2020

I posted about my glow plug controller a while back

After replacing my GP's.. the GPC acted weird.

When I unscrewed the terminals to replace it.. the terminals crumbled.

This video is before I changed it out..

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(Weird, the link isn't showing.. add this after metacafe.com /watch/12073060/bad-glow-plug-controller/

93 F350 Glow Plug Relay Clicking

TheRagnarok

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The Gill Fish

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DaveBen

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The Gill Fish

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TheRagnarok

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mblaney

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Fredrickson

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