I have read a couple of posts in the past that state how you can go about finding your faulty glow plugs and even find out if it's the relay that is bad. My 99 has 183k on it and to the best of my knowledge the glow plugs have never been touched. I say that based on the troubles I have on cold days and the rough idling at start up on those cold days. At this point in time I am going to say it's a safe bet for me to replace all of the glow plugs but I am curious as to how you go about testing the glow plug relay and it's location. What all is involved in changing out the glow plugs? Is it pretty time consuming and what specialty tools if any are needed? I have a good assortment of both standard and metric sockets in the three most common drives along with multiple sets of wrenches but everytime I try to do anything automotive I find myself either making a tool or purchasing one. Is this something that I will run into on this project? I also think that I remember reading somewhere that you have to replace the valve cover gaskets as well when you do the glow plugs but any confirmation on that would be appreciated. With the recent cold spell we have gotten in the KC area I tend to just drive the wifes car when our schedules don't conflict but working a rotating shift makes it a little troublesome at times. If this truck hadn't been so good to me I would consider buying a new one but the thought of making payments again and worrying about every little dent or ding that might occur is far more than I want to take on right now. Thanks in advance for the help.

 

I just replaced my GPR today with help from this site. I'll see tomorrow if it took care of my hard start on cold days. Read the couple of posts I have from today and yesterday and read through the forum. It was very helpful to me.

No special tools needed to replace the GPR unless you don't have a voltmeter. Otherwise the sockets you have will do the job. Good luck

 

One sure way to test your glow plugs and valve cover harness is to ohm check the plug. The outer two prongs on each side of the plug go to the glow plugs. Here are some steps.

1. Check to make sure all connections are good to the valve cover harness gasket.

2. Next unplug the connector and ohm check the outer two prongs on each side of the valve harness connector. They will be slighter larger than the others.Set a Multi meter to the ohms scale and touch one prong at a time while putting the ground on a good ground. You should here a beep or you should see some resistance depending on your multi meter. If no resitance is found remove the valve cover and disconnect the harness from the plugs and injectors. Ohm check the valve harness to see if it's good. If it is than proceed to ohm check each glow plug and if no resistance = bad glow plug.

*The glow plugs require a 10mm socket to remove them*

 

No special tools for GPs. VC gaskets are reusable unless they've been mistreated. The GP wires are the 4 outside ones in each UVC connector. The reading should be between 0.1-2 ohms. From the manual, a good ground is the negative terminal on the battery.

To check the GPR, put a voltmeter from the negative terminal on the passenger battery and on the large terminal leading to the GPs, the one without the red cable. No voltage key off. Key on, should read between 10.5 and 12 with healthy batteries. Should read that for a min of 30secs to a max of 120.

Here's some generic GP system info.

 

It's December, we really need last year's "Cold Weather Hard Start" sticky back on top.

 

I agree, so I found the thread and here it is:

https://www.ford-trucks.com/forums/4...ke-thread.html

 

I realize that the powerstroke uses differant glow plugs than the older 7.3, but the gpr for the older engine has a resister across the normally closed contacts so that the glow plugs do not get 12 volts, its more around nine. I thought that the powerstroke uses the same relay. so if you get 12 volts on the glow plug side of the relay, its bad.

 

Bustech81, Not sure if you are asking a question or making a statement.

 

According to this, "the voltage at the glow plug feed terminal may vary from 9 to 12 volts depending on the battery condition."

 

sorry, bad english. I was asking if the gpr was the same between the older 7.3, and the powerstroke.if the answer is yes,then if you have 12 volts on the glow plug side of the relay, its has failed.

 

Ideally you want 12V on that side, but due to the current draw, most batteries will drop down some. But yes, if it doesn't load the battery at all the voltage stays at 12V or very minimal drop, then you probably have quite a few GPs not working.

 

theres no resistor.