Glow plugs
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5th Gear
Joined: Feb 2025
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Glow plugs
I have the manual glow plug system on my 85 6.9 but when I push the button in and the light comes on it doesn’t ever go off, it also doesn’t start any better with the glow plugs in for 30 seconds, what could the problem be here
Lead Driver
Joined: Apr 2002
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Have you checked the glow plugs for continuity? 30 seconds is too long. Never go more than 10 seconds. I use 6 seconds for 40 degree temperature and warmer, add 1 second for each 10 degree drop in temperature below 40. If 10 seconds at single digit temps is not enough then consider using your block heater. With the block heater try 6 seconds first. The more time you put on them the less they last. What brand glow plugs are you using? When was the last time they were replaced? Use only Motorcraft or Bosch glow plugs.
I use a test light from the battery positive to the glowplug tip. Remove the wire and test. If it lights up the glow plug is still good.
I use a test light from the battery positive to the glowplug tip. Remove the wire and test. If it lights up the glow plug is still good.
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5th Gear
Joined: Feb 2025
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Have you checked the glow plugs for continuity? 30 seconds is too long. Never go more than 10 seconds. I use 6 seconds for 40 degree temperature and warmer, add 1 second for each 10 degree drop in temperature below 40. If 10 seconds at single digit temps is not enough then consider using your block heater. With the block heater try 6 seconds first. The more time you put on them the less they last. What brand glow plugs are you using? When was the last time they were replaced? Use only Motorcraft or Bosch glow plugs.
I use a test light from the battery positive to the glowplug tip. Remove the wire and test. If it lights up the glow plug is still good.
I use a test light from the battery positive to the glowplug tip. Remove the wire and test. If it lights up the glow plug is still good.
Lead Driver
Joined: Apr 2002
Posts: 5,342
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Use care when unplugging. The plugs and wires might be old. Don't want to create a new issue by busting up a plug socket.
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5th Gear
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As I was testing all the glow plugs I noticed one was deeper than the others and as I went to grab it, it fell in the hole, I looked at the glow plug behind it and noticed that that one was just straight up missing. I grabbed a borescope to look in there better and I saw both of the glow plugs down in the hole. Is my best option to just take it apart or is there an alternative
Lead Driver
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5th Gear
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I’ve been driving it for about a month now almost daily, but with not just one but two glow plugs in the prechamber
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can you include photos?
Logistics Pro
Joined: Sep 2007
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From: Western Mass
Did you unscrew the glow plugs to test them and the tips fell into the hole? That can happen with non-oem glow plugs. You should be able to test them while installed using a test light or multimeter as mentioned once you pull off the electrical connector. If your glow plugs have broken off you are in a world of hurt... There are several posts about what to do. If you are lucky, you may be able to remove it with the engine intact, but there is a very good chance you are looking at pulling the head off.
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