A buddy of mine just bought a 1990 F350 and the glow plugs are not working the relay has been replaced and still nothing what i was wondering is if there is something else that controls the relay im not sure were to start i have not had any problems like this on my 01 psd yet thanks for any help or suggestions

 

there are some very good posts in here to show how to bypass and manually run the controller. this seems to be the way to go you only use gloplugs when you need them.

 

Burnt out glow plugs will keep the new style glow plug controller from working.
One burnt plug changes the cycle time to a shorter duration.
Two burnt plugs usually will disable the glow plugs.

The new style system uses resistance feed back to time the heat cycle.
When a glow plug burns out, it changes the resistance the controller sees.

See this thread, there are two ways to check the glow plugs.
https://www.ford-trucks.com/forums/6...low-plugs.html

 

what are u talking about when u say controller and where is it located thanks

 

the controller is located on the very back of the engine. you have to remove the air cleaner to get to it and its under a little black cover

 

This is a picture of the controller/relay with the cover removed.
Use caution when the cover is removed, there are wires direct from the battery positive terminal, lots of juice there.

 

thanks for the post next question is is this what contols how long the glow plugs stay on or is there something else that does that

 

when i start my 92 f350 diesel in the morning after the wait to start light goes off it still takes a long time to start. it starts fine the rest of the day after that, any suggestions?

 

My 89 F350 is the same way. thats what im trying to figure out. What i do is i turn the key and wait for the wait to start light to go out and then i shut it off and i do that 3 time before starting. When i do that It starts right up.

 

I was having problems with my controller basically giving me about a half second of glow before shutting off the GP's so I referred to the picture that Dave S. posted there and hooked it up to a manual switch inside the cab. Boy what a difference. Instead of killing my starter for 3+ minutes every morning I can now just hold the switch for around 10 seconds and she fires up like I was driving around all day. A modification worth it's weight in gold, especially since diesel starters aren't the cheapest. Might be a route you look into.

BTW, thanks Dave for that pic of the controller. It really made the job a breeze.

 

Check your glow plugs.

If you have the new style glow plug relay in that picture, 87 thru 94 trucks used it, th eglow plug heat time is controlled by resistance feedback from the glow plugs to the controller.

One burnt out glow plug will make it cycle for a shorter amount of time.
Two burnt out plugs will make it even shorter.
And with three burnt out plugs, it probably will not cycle at all.

You should be seeing the wait to start light on for 10 or more seconds depending on the night time temps in your area.

 

Mine stays on for about 10-15 seconds. It has been in the high 40's low 50's at night here. Yesterday i didnt even cycle it, i just waited for the light to go out and it started right up. I had a problem with it running last week and i found a leaking injector. I replaced it and it has been starting fine since. I think i may have had air in the line or something.

 

So to install manual switch do I need to go from ignition switch lug to glow plug lug with a push button?

 

If the system you are asking about is on an 87 or later truck, you attach a wire to the white wire terminal on the relay after removing the white wire..
Run the wire inside the cab to a momentary switch.
The other terminal of the momentary switch goes to a good ground.

The ignition terminal is powered by the key switch.
The white wire goes to ground through the controller to complete the circuit and close the relay.

 

Im sorry, wasnt payin attention. Mine is 1986