86 f250 the glow plugs will not come on truck starts fine as long as it is plugged in. changed plug relay still nothing. any help would be great. is there a fuse some where or something else that could be not letting the plugs come on?

thanks glenn
glennfolley@att.net

 

It is not the relay, it is the controller in the rear of the passenger side head.

About 175 dollars for a new one, and it will probably break off when you try to remove it.

A much better option is a manual momentary switch to cycle the glow plugs.

Copy and paste this link in a new window.
http://www.members.shaw.ca/k2pilot/G...%20diagram.jpg

I had trouble with the connector for the engine wires to the cab wires on mine. Should be located close to the passenger side inner fender by the dip stick. Look for signs of overheating or corrosion. I had to cut mine out and splice the wires together so it would make contact. Glow plugs seem to be the first thing to quit working, but they are the biggest load electrically.

 

thanks for the info. any suggestions on how to change the controller

glenn

 

You could soak it down with PB Blaster for a couple of days and try to get it out. But if it breaks off you have to pull the head to get it out.
I have seen several people here that had that problem over the last couple of years. It goes into a water passage in the head is part of why it is so hard to get out, and why penetrating oil does not do much to loosen it up. The other part of why it is so hard to change is where it is located. Good luck is all I can tell you.

When mine started doing funny things I went to manual glow plugs. Smartest thing I ever did to the truck.
With the stock controller they would come on while driving down the road one day, not come on at all the next day, and work perfect the next. But every time you cranked the engine you always wondered if it was going to start.

 

Dave,
My truck is an '84. To wire up a switch on the dash, is it the exact same as the '86? Mine starts good even in 5-10 deg weather but I'd rather fix it before I have to replace GP's. I just put them in a few months ago.

Do I just remove the purple wire on the relay and go from there to the switch, then to B+ with a 10 amp fuse? Thanks.
len

 

I installed a switch yest. Works great.I dont know if 84 is the same. Ifound a hot wire from fuse panel that is hot when key is turned on ran it to switch then to the purple wire on relay leave purple wire off. With a 10 amp fuse on the relay side
Good luck Glenn

 

Well i thought it worked great tried it this morning didnt start the way it should does the controller need to be totally unplugged or just from relay have 12 volts to plugs maybe plugs are burnt or just some of them any way to test plug to see if it is no good ?

thanks Glenn

 

I just changed all the GP on my 85 6.9 at the first of this year do to hard starting in colder weather. (one had a burnt tip) Then found the plastic type connectors between the GP relay and the GP's had overheated long ago, so I bypassed that with a splice, like Dave reported a few replies back. I also found a loose battery cable at the GP relay. That all helped make it start, but I went ahead and added the bypass switch and that did the rest. Starts fine in the cold now, wondered it even started at all with the problems I found.

 

The glow plug system was the same from 83 thru 86.
The same drawing will work on them all.
In 87 the 6.9 had a new style controller and glow plugs that was used thru the 94 IDI.
The glow plugs on the old system have a flat blade connector.
The glow plugs on the new system have a pin connector.

All you need to remove is the purple wire on the relay and wire your push button to the terminal the purple wire was on.
I went to the fuse pannel for my power, switched circuit, that way the glow plugs could not be turned on till the key switch was on. Kids playing and pushing switches could result in dead glow plugs if you go to the battery.

Glennf, check the connector close to the dip stick. I bet it is melted and not making good contact. The 2 big orange wires are the glow plugs on an 86. should be the same on all the old style systems.
To check the glow plugs the simple way, get a circuit tester light. Hook the ground clip on the positive battery terminal. Remove the connector from the glow plug and touch the tip of the tester to the connector on the glow plug. If the light lights the glow plug is probably good. If it does not light it is not good.
The best way is to use an ohm meter. You are looking for a reading between .7 and 1 ohm resistance between the case and the connector on the glow plug. But it takes a good digital meter to read this small amount of resistance. Every once in a while when a glow plug burns out it will short to the case. This will show a good plug with the test light method, but it will show a dead short with the ohm meter. That is the only bad plug that will not show up with the test light method.

 

Thanks guys. It looks like to most work involved here is just getting the switch mounted!!