I haven't, I did however verify connection/continuity from the GP relay to the GP harness before it plugs into the valve cover gasket. I wont plug the truck up tonight and try crossing it in the morning. Supposed to be freezing tomorrow. I'll just have to get an early start trying to get it cranked in case I have trouble. We will see how it goes!

 

You could also use your multimeter to test the large lug that is normally off except when the relay is commanded on by the PCM. This greatly reduces the chance of spark, arc, equipment damage or injury.

Shorting the two large lugs is a temporary fix for a failed GPR. You are attempting to identify the failed part and the best way to do that is with the proper test equipment and method.

You will be testing for volts DC with the red probe on the normally off large lug and the black probe on the battery ground lug.

 

I will try that as well Sous.

Edit, I tested voltage on the input and the output of the GP relay. The output was 12.48v. input was like 12.52v. not sure why there's a little bit of loss between the two posts but I don't think .4 volts makes that much of a difference.

I did cross the GP relay this morning before starting and the truck fired right off but, it was almost 50° out so I don't think that means much. Crossing the relay did also turn my little glow plug light on.

 

The voltage drop was most likely due to the small amount of resistance in the material make up of the relay contacts inside the housing.

Also, the drop was 0.04v, not 0.4v. This number is a small detail with significant ramifications if it were noted incorrectly.

The good news is that southern AL has a light winter and your GPR appears to be functioning properly.

 

Well, it gets down to around 13-18 degrees. 13 being the coldest I've seen here personally. But it is light compared to Alot of places!

I am glad the relay is working properly, and will just plug my truck in until my new gp's get here and I will test my uvch's while in there. Going to tear half my motor apart Saturday and start painting! Parts will be here Sunday. I'm excited!

 

Enthusiasm is wasted on the young. Between u-joints, injectors, tires, and anything else automotive-related these days.......it gets harder every day to go out and do stuff.

I'm 30-45 minutes away from having a 350 on the ground from a 97 Chevy (installing a new engine) but here I am procrastinating - trying to find a reason not to get dirty today.

 

if there is a high ohm reading on all of the GPs, that wont be doing much to help anything

 

I find it nearly impossible to believe that all eight glow plugs gave up the ghost at the same time.

 

Truck has like what, 400,000+ miles on it. Likely original gp’s
I do not find it odd that they may have all failed over a period of the last 20k miles.

 

Sir, please see the quote below and the corresponding quote source link which will direct you to post #11 in this thread. This very small detail was buried deep among the other posts and if you are anything like me, you do a "knowledge dump" each time you sleep... In all reality, he probably had a couple working last winter shortly after installing new injectors. Those stubborn and unwilling to give up GP's probably got him through the winter with fresh parts in other critical areas. Now, those lone survivors have most likely died as well.

Quote source:https://www.ford-trucks.com/forums/1...l#post20628874

 

440,000+ miles currently. I just changed the oil 500 miles or so ago and now I'm doing a oil cooler. I picked up new oil. Putting drained oil back in didn't feel right

It is very possible they have been going out 1 at a time for the last 21k miles from the time I did injectors. I think it's more likely to be that than for both the new vc gasket and harness on the driver side and the 25¢ mod passenger harness to have messed up at the same time. If the harness had issues I would think I would prob have a misfire or something anyway. Either way, I will def ohm the plugs individually on the bench once they are out. Might as well!

 

That is a good point and possibility.

 

This morning was below freezing when I tried to crank the truck. Windshield frosted over, whole nine yards. Frost all over the ground. I waited 20 seconds after the WTS light and tried cranking for 20 seconds. Not even so much as a hit. Turn the key off and got out and crossed the glow plug relay for 30 seconds and got back in the truck and it fired instantly. Now this is weird. The relay is working, as I have verified multiple times, but still, the glow plugs only work if I cross the relay? That's weird. Or could it just be coincidence? I have heard before to let the truck sit for a little bit after attempting to start to let the smoke in the cylinders build heat. could the smoke sitting in the cylinders of generated enough heat to fire? I don't really know what to think at this point. Maybe this goes back to when I had the injectors sending feedback through the glow plug harness. Maybe it messed up the glow plug relay some witch away. I'm going to take the terminals off and clean them. I don't really know what to think about this. It could have just been a coincidence. I do know that I have glow plugs and a bunch of paint so I am going to go ahead and put glow plugs in and paint my valve covers and whatnot.

 

Just put a new relay in. Mine failed before the truck even made it to the 100k mark, so you've had a good run with this one. Your little LED will light off with a millionth of a watt compared to what the glow plugs require and it's very likely in my mind that the contacts are fried to the point that there's enough for the LED to light, but the glow plugs are simply not getting the amperage required to heat up.
BTW, my "glow plug relay" is the Intake Air Heater relay, mounted right next to the glow plug relay. When mine failed, I got the truck going one morning in high altitude Colorado while on vacation by disconnecting the heater and and pressing the IAH relay in to GPR duty. It's been that way ever since and the intake heater element hit the scrap bin more than ten years ago now.

 

I haven't even had a Sprint with this one yet. This is a brand new trombetta relay that I just put on a couple months ago. And I tested it with a voltmeter that I'm getting full voltage to the terminal on the output. Maybe when I installed my glow plug light somehow it affected the connection there. I don't see the relay being the problem but, I will just have to test and see. But maybe the connections are dirty or something. I'm definitely going to clean the terminals first. Before I replace it anyway. If I do replace it I'm going to order another trombetta relay because I hate the parts store relays. They don't last at all.