Glow Plug Controller Clicking on and Off, Not heating glow plugs.

[sheepman]

I replaced my Glow Plug Controller (GPC) and right off the bat it just started Clicking and not Warming. The last GPC just stopped Working, I tested the old GPC and found the relay to be good and the computer part to be bad. I also tested the relay on the new GPC and it is in working order. I do have a engine wire loom from a 91 on the engine (long story). Any ideas would be great.

[RayHell]

This sympthom is typical if one or more glow plugs are bad, or the wiring is bad somewhere.
The GPC does this when the load current through the GPs are lower than normal, for example if one GP is burned out.

[Mr_Roboto]

Like Ray said, with just one bad GP the controller will cycle shorter. Each additional bad plug makes the cycle even shorter to where the GP's won't heat up at all.

All my 7.3's have had a manual control wired in so that you can still start the motor if the controller is acting up.

You run a wire from the small terminal on the passenger side (this has a white wire on it), through a pushbutton switch, and to any good ground. Now any time you push the button the GP relay closes. There is no need to unhook the existing white wire unless you want to completely disable automatic operation.

[sheepman]

I will look into bad GPs, I just replaced them Before the old GPC went out. Maybe the old GPC overheated them and there is a bad one in mix. This is also the frist time for me to have a bad glow plug cause such trouble. Does any one know the what the voltage should be in the two yellow power leads?

[cdnsarguy]

.....7-9 volts would be good.....

[OkieGringo]

What brand GPs did you put in? Autolites are famous for burning up (and causing MAJOR engine damage, or at the very least, making it necessary to remove the heads to get them out [img]/ubbthreads/images/graemlins/eek.gif[/img]) within one week, even when new. We recommend using ONLY Motorcraft ZD-9 GPs. [img]/ubbthreads/images/graemlins/smokin.gif[/img]OkieGringo

[sheepman]

For the past 16 Years this truck has only had Motorcraft plugs. I know all about the troubles other plugs can cause. [img]/ubbthreads/images/graemlins/mad.gif[/img]

I have tested all the plugs with a test light and they all light up. I still know that I have to test the voltage at each glow plug.

OkieGringo I used your ground bypass push button and that worked. I also check and repaired my ground wire. Anothor thing I did was remove the plug wire from each and every plug. After doing that I hooked one and only one plug up at a time. Turned the key and still got the click, click.

So, today I am going test the voltage for each GP and see that goes.

[Mr_Roboto]

For the GP controller to cycle properly, you must have the proper resistance from ALL 8 glow plugs. If any are unplugged or have improper resistance, it won't work right...

Just a point of clarification.

[sheepman]

Today, I went to NAPA and got the push button for the GPC ground bypass. I got it all put back together and tested it.

I turned the key and "Click, Click" I then pushed the bypass button for 8 sec and the clicking stopped. The GPC started clickin again after I relessed the button. I turned the key and rolled the motor 3 or 4 time and it fired up. However, it seemed that one maybe two of the cylinders were not fireing as they should have. The air temp in the garage was around 55 deg.

It's possable that I did not let them heat up enough. When I get the chance I will pull all the plugs and inspect them and check the resistance.

[sheepman]

Is it Possable that the Temp sensor is Not working and causing part of this.

[sheepman]

I got it!! Bad GPC after all the test and replacing the ground wire, 2 GP lead wires, and 8 new Glow Plugs. Cleaning out the Little brass Slip conectors on the GP leads. It's a bad GPC.

THANKS EVERYONE FOR THE HELP.