i have a 1984 F350 diesel I have no power to the glow plugs. Also the wait to start light will not come on .What causes this problem and how can i fix it.

 

From Hayes techbook- on 6.9 liter models thru 1986, the system consists of eight glow plugs,a control switch, power relay and after glow relay. This includes a wait lamp latching relay, wait lamp and wiring harness, which incorporates *** eight fusible links*** (this might be the problem) one to each glow plug. located between the wiring harness and the glow plug terminals. the system is activated when the ignition switch is activated.

The control switch is located near the rear of the engine on top of the intake manifold.

The power relay is located near the battery on the right inner fender in the engine compartment.

If you have a volt meter you will have to test to see if first you are getting power from ignition switch to pin 3 of control switch.

 

I would bet a good steak dinner that it is the control relay at the back of the motor.

 

Not to many members still use the OEM gp controller setup, most have moved to a modification and a push button.....

heck out this page... http://www.members.shaw.ca/k2pilot/

 

My bet is the controller in the rear of the passenger side head is dead.
To check the relay mounted on the passenger side inner fender well.
This is a picture of what you are looking for.


Also this has some non stock wiring on it.

The terminal with the orange wires that go to the glow plugs and one black wire on it that goes to the wait to start light.
The purple wire on the right goes to the controller. The green wire is not stock that is spliced into the purple wire.
The black wire on the left must go to a good ground.
You can not see in this picture the other terminal that has a red wire to the battery positive terminal, probably routed through the starter relay mounted on the inner fender above the glow plug relay.

Test the black ground wire for a good ground, a test light with the ground clip on the positive battery terminal will do. If the test light lights go to the next step. If not repair the ground.

Next jump battery voltage to the purple wire terminal. The relay should click and the wait to start light should come on. If it does not click the relay is bad. If it clicks and the wait to start light does come on, either the controller is bad or the engine to chassis connector is bad.
That connector is located near the oil dip stick. It is a white connector and two of the wires in it are the big orange wires from the relay. Look for signs of melting near the orange wires and try to unhook it. If it comes apart and reconnects easily and does not look melted then I would move on to the controller.

The controller is expensive and there are some bad stories about it breaking off when trying to remove it from the head. Since it goes into the water jacket, if it breaks off you have to pull the head to fix it. That is the reason many people are going to manual glow plugs if it is bad.

The purple wire you jumped power to to test the relay is where you run power to to convert to manual.

 

Thank for all your help.Already put new relay on will try and convert over and see what happens

 

checked glow plugs not a one of them will light up with test light. Also I noticed that if I touched the wire to the glow plug with the test light that the test light would light up is this supposed to happen. Thanks again for all your help.

 

Yes it would because the "Wait to Start" light bulb is completeing the ground path.

Go down to Autozone and get a set of Motorcraft/Beru ZD1A Glow plugs, 9.99 each.

I am assuming you have the ground clip on the test light on the positive battery terminal to test the glow plugs.

 

Just want to thank everyone for all your info . Went to autozone got eight new glow plugs and a momentary switch, Went out this morning put them in husband now up and running again. Been trying to get him to check plugs for a while now with no luck ,so after getting on here yesterday and finding out what to do .I have him going again, should have registered this in my name instead of his, anyway thanks alot.