Hi I have an 86' f-350, 6.9. and for the last few weeks the glow plug light was coming on while driving, well after it warmed up. now it wont start at all, it has a new lift pump, and it is getting fuel now. Question. what cycles the glow plugs? is there a sensor that tells it, that it is warm? if so where is it? If not what controls the GP?

 

the 86 has a sensor in the head that controls the glow plug controller , check your fuse links first and wiring

 

Hi, chances are that all of your glow plugs are now burned out. The controller (thermal timer- pre glow) is located on the left rear of the engine and the relay should be on the right front fender well (not the wall) in front of the battery. The system cycles for a short period after it is started by means of a signal from the alternator. There is an afterglow relay probably under the dash. Be careful removing the plugs because over timing might cause tip distortion and breakage upon removal. Hope this helps.

 

Try a test light on the GPs...... remove the spade connector then with the clip to battery positive, touch the light point on the spade terminal of the GP. There should be a light..... if not then they could be burned out. What brand were the GPs.

Do not try removing any before reading......... http://www.members.shaw.ca/k2pilot/

Rgere is a sequence to removing the GPs if suspected of being burned out...... if done wrong head removal is required............ Check recent posts here I just coverd some of that for one member last night. "is this safe to do "

 

Glow plug controller is in the back of the drivers side head, round cap with about 8 wires coming out of it.

When the controller fails, it usually turns the glow plugs on, burning them out.

This is the relay mounted behind the passenger side battery.


After you fix the glow plugs that are toasted, after the engine starts, remove the purple wire from the relay.
That way the controller can not turn them on.

Manual glow plugs are easy to hook up, but usually not a good idea if other people drive the truck.
They never understand push the button for 10 seconds, then start the engine.

Either they hold the button for 30 seconds, burn the glow plugs or 4 seconds and toast the starter from excess cranking.

I am telling you all this because removing the original controller is a risky thing.
It goes into the coolant passages and has been known to twist off before it comes out of the head.
If it twists off, you will probably be removing the head to get it out and block the coolant off.

To install manual glow plugs, find a fuse that is hot only when the key is ON.
Run a wire, can be small gauge to a push button or momentary switch and attach it to one terminal.
From the other terminal, run a wire to the relay terminal where the purple wire was attached.

The glow plugs are now ready for manual control.

To operate, turn the key to ON.
Push the button for 10 seconds.
Start the engine.

The push button or momentary switch needs to be spring loaded, so it can not be bumped ON and burn up the glow plugs.
Do not use a normal switch because of this.

 

I went to the Auto Lite sight and looked up the glow plugs for the 6.9. Well they have 1107 with a *2424 note. This note says to "use until inventory is depleted". Glow plug # 1115 replaces the old one 1107. I guess "they" want to sell all of use the junk that will tare up the engine before we can buy the 1115. Oh after you purchase a new engine, that supply may not be depleted by then.