today i had to cycle my glow plugs like 10 times and it only 47 degrees last year had same problems so i replace the relay and all the glow plugs and she fired up in the negatives without being plugged in and this year back to the same thing i think there was notting wrong with the old ones jsut alot of carbon depostie on the plug but they still lit up when i put them to a 12 volt source and burned all the stuff offf of them wat do u guys think it is now need new glow plugs again and i put the motorcraft ones in there ????? help i hate replcing things twice

 

Welcome to FTE. The odds of 8 Motorcraft glow plugs failing within a year are pretty slim. Since the tips of the plugs are exposed in the cylinder, I don't think a 12v power source will burn off anything that the combustion cycle doesn't.

Let's start by testing the relay. First you need to understand the wait to start light (WTS) does not have anything to do with how long the glow plugs are actually on, it's more of a reminder. Depending on engine & outside temps, the glow plugs will come on between 1 - 120 seconds each time the key is on.

To test the relay, grab a volt meter or even a simple test light. Leave the key in the OFF position and test each of the 2 large lugs on the GPR (glow plug relay). With the key OFF, one of the large lugs will have the 12v battery reading and the other one will have no reading. When you first turn the key on, the large post with no reading should no jump up to around the 12v reading, or if using a test light, you should see voltage on the second large post.

If you're looking for a short cut test, grab a screwdriver and lay it across the 2 large posts of the GPR. Yes it will spark, and yes the screwdriver will get a little warm, but hold it there for 30 seconds. Then get in and start the truck. Just start it like a gasser ignoring the WTS light since you just manually lit the glow plugs.

 

Hey chris, do you have the link or able to tell me real quick how to hook up an led to the GPR to see when it is on.

 

I'd have to look for a link, but your two options are either
1) hook the positive wire to the second large post on the GPR (going out to the GP's) and ground the led, or
2) hook the led to a 12v source and run the ground to the small post on the gpr that gets the signal from the PCM.

You'll be surprised how long the things stay on, especially in the summer months.

 

i put one end of the test light on the ground of the battery i have the key off and one of the post light up and then i turn the key the other side dosent no light up with the key off and on still dosen not light on the test light so do u think its just the realy even tho i replaced that too last year at the bigging of the year?

 

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i put one end of the test light on the ground of the battery i have the key off and one of the post light up and then i turn the key the other side dosent no light up with the key off and on still dosen not light on the test light so do u think its just the realy even tho i replaced that too last year at the bigging of the year?

 

If the 2nd large post does not light up, then that means there is no power going to your glow plugs. Either you have a bad relay, even though it's only a year old, or you have a wiring issue.

Try the same test with your test light, except this time instead of hooking the end of the test light to battery ground, hook it to one of the small posts on the GPR and stick the test probe on the side that is always hot with the key off. Turn the key on and see if the test light comes on. You'll have to do this test with both of the small posts on the GPR since I don't remember which one is which off the top of my head, but the computer is supposed to send a ground signal to one of the small posts when the key is first turned on. The ground signal is what activates the relay.

If you need a new relay, you can save some money by getting the NAPA 109 relay, or upgrade to the Stancor HD relay, or even just wire in a push button switch that will activate the glow plugs without the use of a relay. Until then, use the screwdriver trick I mentioned above to get the truck started.

 

i put the one end of the tester on the samll wires with the key off and put it to the power side and they both acted as a ground signle cause the test light came on on both small post and now relay is working fine and truck started right up im wondering if just messing up or not wat do u think? one of the small wires is from the pcm and wat the other wire go to ?

 

Here's some good readin' to test out the GPR.

Welcome to guzzle's Stancor GPR replacement Mod Web Page

 

most likely you fried a GPR. My 2000 F350 cc drw had a new GPR on it last year, mid summer. I also installed the LED mod. Just in the last week the led started working intermittently and now is not working at all. Checked incoming power to the relay and its getting juice to activate, just not outputting. Time for the stancor mod.