Done alot of reading today on this and a cold starting issue.

I done the Woodall(sp?) test by the video posted. With the KOEO the pink wire (GPR) will have voltage about 2-3 seconds then 0v, the feed to the glow plugs will have voltage for a while haven't timed it once the voltage is 0 here the pink wire has voltage again. Now according to the video during the KOEO test at the GPR you can ground this pink wire and hear the GPR "click" on/off correct? If so mine doesn't. I think this may be my problem. I couldn't find the post with the NAPA part # for the relay can someone provide it or another # for a suitable replacement.

I have two cheap multimeters, I ohmed the glow plugs at the valve cover and got an open reading on all, this was the first two and last two on each side. Hopefully its the meters but two of them??? Would the truck even run if none of them were working? I'm in NC so this last cold snap it really showed up. I plugged it in overnight and had no issues.
Thanks

 

First off, your Gp's only help get the engine started in cold weather. They ONLY hekp atomize the diesel that's being injected into your cylinders on start up, when it's cold. They only stay on for 2 minutes max. (May be off by a minute one way or another) if the engine oul temp is below a certain temp. In the summer, GP's may not even cycle. To tst your GPR, (glow plug relay), take a meter, run the ground to a good ground, like your battery neg. then take your + lead, and test the large stud on your GPR. It should have 12v continuous, whether key is on or not. Now, flip the key to on, with engine still off, and your other large stud on GPR should be energized for a period of time as well. The GPR will stay energized longer than your Wait To Start light stays on. Hint- this is why many do the GPR LED mod. After the GPR is no longer energized, crank it, and it should fire right up. I don't know how to ohm the GP's out. I've always been of the mentality that I fix things that make me wonder if the truck will run/start. However, I use my trucks daily for my business, and can't afford to have a no start situation at 2 am with 3" of snow on the ground with 7 commercial lots to clear. When I wonder about my GP's, I change them, but make sure you only use Motorcraft ones. I personally have had 2 pull 2 different cylinder heads due to stuck/frozen autolites in 2 different engines. A bit long winded, but hopefully it helps.

 

The relay does as you stated, voltage wise. My question was about grounding the small pink wire (the one the pcm will ground) when you do this it should cycle the relay according to the test video.
Thanks for the help

 

Yes, when that post gets a ground, the relay should be energized and both large posts should have battery voltage.

 

So would you consider the relay bad when even after it times out and gets voltage back on the pink wire and I ground it no voltage or click on the GP feed wire?
Would you have a part number for a good replacement relay.
Thanks

 

The napa # you asked for is gpr 109, Not that good any more as its made in China now. Oem is good, and many use the Stancor/White Rogers. There are lengthy threads on that one.

 

https://www.ford-trucks.com/forums/7...pr-system.html

In a bit of detail

 

Just an update
Ohmed all glow plugs at the VC connector readings were not instant but came down to 1.5/1.6 ohm's on all 8. Did the other test with the test light all light up. Went another route to. One lead of my meter on battery + and the other on each pin on the vc connector all read battery voltage.

Tested GPR on constant 12v lead with KOEO 11.6v on the feed lead to glow plugs 11.5 v.
Looks like to me everything is in check. Everyone agree?

Haven't ever had a problem with it not firing and running when cold until this year. It would start up then go back dead a couple times usually third time it would run but romp a few seconds then smooth up. I run the 15w40 oil. Read where some changed weight and this helped. If I plug it in no problems at all. Got me puzzled. Probably going with the big GPR anyway though.

 

Grab a gpr109 for a test. It cost me $25 bucks I think.

If your sure GP system is good, look at the battery's

 

Replaced both two weeks ago.