what contols how long the glow plugs stay on i know the relay turns them on but what turns them off is there some sort of timer on these trucks or what

 

the PCM controls that

 

If you accidently got the wrong calibration code burned on your chip then the glowplugs will stay on all the time. This will ruin your glowplugs. For example.... If you are a California coded truck then you need Cali coded burns on your chip.

Diane

 

I have disabled computer control of that system on my truck and replaced it with a push button on the dash.
I live at sea level in a mild climate that doesn't freeze all that often, Seattle, WA.
There's plenty of mornings where the frost is hard and it's well below freezing, but only every forth or fifth year or so will it get below 15 above zero F overnight.
On those mornings all I have to do is hold the button down for a ten count, start the engine, and then hold it for a few more seconds while all the cylinders warm up and begin firing on thier own. At that point, the glow plug's job is done and the only reason that Ford (or all the other diesel engine manufacturers) keep them on is to control cold engine smoke. Sort of a way to keep the smoking complaints on a diesel down to a dull roar. It's amazing to me how many people percieve a smoking exhaust pipe on a diesel engine as something that is wrong and needs to be fixed.
IT'S A DIESEL!
It's an easy conversion, just disconnect the LR small wire from the glow plug relay and tape it off. Now run a wire from that post into the cab where you will run the current through a push button switch that will turn off if you release the pressure. The kind that you must hold on for it to stay on, like a starter button on an old tractor or something. From the other post on that switch run it to a good ground location.
You now have manual control of the glow plugs whenever the ignition is switched on.
On cold mornings you must hold the button down to heat the glow plugs. I find that I can skip the glows at any temp above 55 degrees at sea level. The higher in elevation you are the warmer the thresh hold temp will be. After a little practice you will get a feel for it. The truck will let you know if you need to heat the glow plugs or not as it will be hard to start and/or a LOT of smoke.
The wait to start light will still come on and you will probably get a glow plug relay code. On my truck I do but it doesn't turn on the check engine light so I don't worry about it.

 

thanks guys that explains alot

 

I just did mine.$13 each at autzone for bosch.While I was under there I found the injectors loose.They are known to work themselves loose.Re-torque them to 10ft.lbs and the rockers to 20ft.lbs.There are plenty of write ups on how to do this.