Glow plugs heat at hot start

[DrCharles]

I got the truck with several bad glow plugs 4 years ago and replaced them all with Motorcraft. The 7.3 IDI starts quickly, summer or winter, and as expected the glow time (and "Wait to Start" light) gets longer with colder temps. So far so good.

But the controller has always called for a minimum of a few seconds of glow even at a fully hot start. If I don't wait and just fire it up, the GPs then cycle off & on for 3-4 seconds after the start. The 7.3 was originally NA, and I added a factory turbo setup (recently improved to a CDD rebuilt with Stage 1 wheel upgrade) - the controller is mounted in the stock position on the right valve cover which I got from a turbo engine. The thermostat is operating correctly (i.e. the engine is not colder than it should be).

I have read in many places that there should be no (or a brief blink of the light) when the engine is at operating temperature. Is my controller just off a bit, or could a replacement be designed that way on purpose to reduce emissions? Will it significantly reduce the life of my GPs if I leave it as is?

 

[IDIBRONCO]

Keep in mind that I haven't owned (not running projects aside) any trucks with the 7.3 style controllers. From what I can remember, it's normal for them to cycle the glow plugs, even when hot, for a short time. The few seconds that you mentioned sounds right.
I can't verify this, but I've also been told that if you start the engine before the controller shuts off, it's ******* your glow plugs. Hopefully someone can verify that or say for sure that it's not true. As for me, I plan to put all glow plugs in my drivers on manual control.

 

[asmith]

I always have at least a short Wait to start time, no matter the temperature out or how warm the engine is. Has been that way with both my trucks. I thought a little glow plug action was normal.

 

[Cubey]

My 6.9 RV with the updated solid state (doesn't break stuck on) 6.9 controller (before it died last winter) would only not activate the glow plugs on a heated up engine in summer when it was very warm out. It was a rare thing. Supposedly it's not supposed to activate them above 165° coolant temperature, at least on 6.9:

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[Greenie]

Mine's always done that since new. If the motor is at normal operating or in the ballpark I start it without waiting. The glow plugs cycle a few times by design.

 

[DrCharles]

Thanks... looks like "it's not a bug, it's a feature" at least on the 7.3 version. I would have thought that not heating the GPs when they are not needed made more sense.

 

[tbowker]

I have the GP controller delete on my truck. I don't even bother with GP's unless it gets to 60's or less, (I live on the coast in Central Florida) then depending on ambient temperature I'll hold the button for a 6 to 8 second count and then hit the starter. It'll fire up in two revolutions or less, then I don't touch the GP's again. Am I doing something wrong? Should I glow it for a bit after it starts when the temp hits the 40's? Seems like that's what the controller is doing from reading this thread.

 

[Old Goat]

Sound ok what you are doing.

In the summer, I still hit the Toggle Switch 5 - 6 Sec. in the morning, then not at all the rest of the day.

Winter time is different, 8 - 10 sec in the morning. And she usually lights off with R-r and comes to life....but there are those mornings when it has been in the teens take a few R-R-R-R-... and some more glow R-R-R-glow while R-R-R and she comes to life.....and sounds like the Rods are ready to leave home.....
With 344K miles, she isn`t as tight as when she was new.

The Controller on the 86 didn`t work when I bought it 10 yrs ago, so haven`t heard one to know what they do.

Tho this discussion is about the later 7.3 style.
Do the same thing, but set up different.


Goat

 

[tbowker]

Okay, that's good to hear. It makes a bit more noise when it's frigid outside but within about 10-20 seconds the clatter is mostly gone, normal engine noise after that. I attributed that to a typical cold engine and wasn't overly concerned... until this thread. Thanks.

 

[IDIBRONCO]

Should I glow it for a bit after it starts when the temp hits the 40's?

I don't on mine until the temps get down into the teens.

 

[ihc1470]

Have not had mine all that long, even hot it lights up for a few seconds. I normally wait until it goes out. If in a big hurry I start it and they are off after couple seconds.

 

[tbowker]

I don't on mine until the temps get down into the teens.

Okay, that's good to hear. Thanks.

 

[DrCharles]

How long do glow plugs usually last? Is there a recommended replacement interval? Or do you wait for one or more to fail, then change all eight...

 

[Cubey]

How long do glow plugs usually last? Is there a recommended replacement interval? Or do you wait for one or more to fail, then change all eight...

There's no good way to say how long they'll last. Depends on the climate, how often is it driven, etc. I bought an IDI motorhome in January 2019 and put a bit over 18k miles on it until I sold it a little over a month ago. The glow plugs never got touched while I had it. Who knows how old they were when I got it. They were still fine when I sold it.

 

[IDIBRONCO]

I agree with Cubey. Mine have been for around 4 1/2 years. I know that I've put on more than 18,000 miles and they're all still good. Manual control does make a big difference in the lives of glow plugs. They're used usually once a day. Maybe twice in the winter time.