Kwikkordead described how to wire a switch that would manually activate the glow plugs. I found the small wire connected to the GPR that is not energized while the engine is running. Once that wire is connected to the switch, the wire leaving from the switch needs to be connected to ground. Does the switch need to be activated before you turn on the ignition or can you turn on the ignition to "wait to start" and then activate the switch.....or does it matter? By grounding the wire through the switch, will this turn the glow plugs on any time I want?

 

I posted this earlier: yukonsly, the way that the GPR works is: one of the small wires to the GPR has constant power all of the time (+12volts), when the PCM turns on the GPR it grounds (-) other small wire to complete the circuit.

You can do either, activate the switch first or the key first.

Yes, it will activate the glow plugs anytime that you want, because you are taking the PCM control out of the circuit.

 

This is a popular topic

Yukonsly

 

Why would you want control of your plugs? Is this mod to bypass a faulty GPR? More info needed for me

Cowboy Steve

 

Your glow plugs work everytime you start your truck, regardless of the outside temp. I recently became interested in the topic when my valve cover harness conection started to smoke. It became apparent that the wires were worn and shorted. Upon closer examination, my remaining 3 valve cover connections started to burn as well. While I fixed the problem by replacing the wires, I wanted to know why the wires were fried. The problem is that the glow plugs are energized everytime you start your truck. Living in North Carolina, I would venture to say that 90% of the time, my glow plugs are not needed to start the truck. Our temps just don't get that cold. I wanted to stop the glow plugs from energizing when they were not needed. This would eliminate the excess wear and tear created by glow plug activation every time the truck is started. Manual glow plug deactivation addresses the cause of the problem.

 

To clarify: from what I have been told by my local Ford diesel mechanic, and from checking on several trucks that I have worked on;

The 94 & 95's activate the GPR (and glow plugs of course) everytime you turn the key on. PCM programing. On these trucks the PCM read input fromthe oil temp sensor and baro sensor and uses that input to determine how long to leave the glow plugs on.

The 96 & 97's PCM programing is different, everytime that you turn the key on, the PCM reads input from the oil temp sensor and baro sensor to determine "IF" it should activate the GPR. On thses trucks the glow plugs are NOT activated with every key turn if the engine is warm and/or the outside temp is warm.

dsheleg, living in GA. I only activate my glow plugs when it is in the mid 30's and below. It saves alot of wear & tear on the GPR, wiring and glow plugs. I've had it on my truck for about 5-6 years. I really like it and have never had a problem starting.

 

Will the grounding switch still accomplish shutting off the glow plugs on my 97 f350.

 

Yes. Refer to post #2 item #3.

 

Know Im tuned in! lol, atta babe boys, way to save yourselves some money! My rig is a '97 so I shouldn't need this mod acording to the Plowhand post. But good lookin out!

Cowboy Steve

 

This is incorrect info. at least for my '96. It does read the temp to guage how long they stay on, but they will come on no matter what the temp is, how long is dependent on the motor temp. No matter what the temp is, as where I am the swing is very broad, the batteries get cycled every time I start it up (just watch the amp gauge). Flip my Gp switch and the batteries never take a hit. Confirmed with an amp meter.

 

It depends on what code your pcm is flashed to, and I've heard but can't confirm there may be program differences depending on where the truck was sold.

I have my GPR wired to a switch so I can disable or let the PCM take control. Rarely need the glow plugs in california.

 

Very seldom need the glow plugs down here in L.A. (LOWER ALABAMA) so I just unplug the lead at the GPR when the weather warms up and plug her back up somewhere around December. Sure saves on the overall GP system...

 

Same here, I can disable in the summertime by a switch. That is my very point I stated, at least on mine they come on all the time.

 

walt1968, you are probably correct, I never doubted you. I was just going by my personal experiences on the several trucks that I have worked on and what the Ford diesel mechanic (who is very good) told me.
But as with all things vehicle related, you never know. My 1995, with a Nov. 94 build date, does not have a de-gass bottle system, it just has the old style recovery tank. But when Ford puts in the VIN for parts it shows the de-gass bottle system, it also shows that they never had my style recovery system in our trucks? Go figure. My truck was a one owner truck when I got it with no mods, factory orginal.
So...like JOAT said, it probably has to do with which PCM programing you have, which "should" relate to your build date. I do know that Ford keep changing the PCM programing over the years to correct and/or improve performance issues.

 

LOL I have a mar 95 build with the degas bottle. Getting quotes for radiator and hoses some places show it with, others without. When you look at the parts screens there doesn't seem to be any agreement on when the changeover occurred