My glow plug light won't go off.

[RNation]

It's me again. For some reason in the morning when I go to start my truck to let it warm up the glow plug light comes on and stays on. I shut the the truck off after about 10 to 15 seconds though. Then I keep turning it of and on till it eventually works right. But this morning it wouldn't, no matter how many times I turned it on and off it came on and stayed on. I finally just unplugged the glow plug controller switch or the glow plug inhibitor switch (I forget what it's called), the one in the back of the driver side head with the 5 or 6 wires coming out of it. So far when I get the truck warmed up the glow plugs do go off and everything works fine, it's just the initial warm up that acts funny.

Doesn't the controller switch control the glow plugs on/off based on the coolant temp (I think there are 2 more temp sensors for glow plugs, 1 on opposite side of valley from controller switch and the other on passenger side next to back injector)? So if that's right my thoughts would be a faulty controller switch. Oh and the controller switch, glow plugs, the temp sensor on the passenger side back of head, ignition switch, and starter solenoid are new. I thought I had the glow plug system all covered but apparently not

 

[Missy Good Wench]

Glow controller (device you unplugged) is going south.

You can find these on ebay from time to time at good prices.

Either replace the controller or wire in a manual button to run the relay.

The inhibit switch is on the opposite side near the same spot and has a two wire plug.
The best thing to do with the inhibit switch is to jumper the plug and forget that thing.

They are notorious for failing and leaving you with no glow system operation

Missy

 

[RNation]

thanks for the quick reply. I think i'll get a replacement glow controller because it should be under warranty and I paid like $200 for it.

I am thinking though if I have these problems again to hard wire it. The only thing I was unsure of was in the winter time how do I know when to turn the glow plugs on, obviously before I start the vehicle but what about after it's on?

 

[WarWagon]

I would not turn them on with the engine running. They do this for emissions - as a cylinder may go cold and quit firing. Last time my glow plugs turned on with the engine hot and running in the 1988 suburban they went out - the exhaust. Bad sensor allowed them to come on with a hot engine.

But if the engine is cold enough and you have a misfire with white smoke you can think about it. Hot engine and glows are bad...

 

[Missy Good Wench]

If the engine is in good shape the glow plugs wont be needed once the engine has some heat in it.

The original design uses about a 8 second initial glow cycle and then the unit will continue to do an afterglow cycle of On/Off-On off a few times to keep a cold engine running smooth and eliminate excess smoke.

You can do the whole process easily with a push button to activate the glow relay.

8-10 seconds on (cold using 60G plugs) once the initial cycle is done, start the engine and then cycle the plugs for the next 30 seconds or so every 5-10 seconds or as needed to keep the engine running clean.

The 60G plugs are really tough and unless you get stupid with the cycling you wont have any issues.

Another secret is making sure that the cold advance is working correctly as well as the fast idle solenoid.

With an engine thats in good shape (good injectors and compression) the glow plugs are usually only needed for the initial lightoff.

The later 6.5's with the DS4 don't use the long winded afterglow that the 6.2 used.
This is due in part to the higher injection pressures.

Missy

 

[RNation]

So would it be better to just hardwire them? I talked to the guy I bought the controller from and he said he doubted it was bad and when I asked him about the warranty he said he'd have to send it in to manufacture so they could test to see if it's their fault or mine. It's probably mine, hooking a wire up backwards or something, because the controller's only like 3 months old and truck wasn't working half of that time.