If I'm not mistaken on all the trucks (99 - 03) glow plugs are ALWAYS cycled on for ~2 minutes regardless of temperature. Can you leave your ignition on for 2 minutes with the manual ground and see if it kicks off? It's on a timer

What you are describing is exactly how mine behaves, it's always switched on but turns off after the allotted time above.

 

I believe that @HD Rider is onto something here and you may be looking to the right for the problem when it is staring you in the face from the left.

 

I might have other issues but "hard to start" is relative, it isn't really that hard to start now but it does not start a quick as it use to, maybe now it is 5 -10 seconds. But I know that the GPR is not closing even briefly as the book says.and when it gets cold it will be a bear to start, i think. It,makes sense to me to try to fix the GPR issue first.Whatever input is lacking or other error could be caausing more than the GPR issue. I didnt see any pids that were out of range and there were no codes. Also since I'm not aware of any other issues it would be hard for me to troubleshoot them. However, I will send more time looking when I get it running later this week. I didn't see any issues with intake air, forscan had it about reading right. The info I have is that the oil temp and the baro are the two inputs to the pcm, not air temp, .but since mine is actually a 97, that be true. Chatanooga Dieesl has contacted me and said the core I sent has no faults and the ground for the GPR works on their bench test,. so, faulty PCM now seems very remote.They have suggested further testing to determine if some sensor or wiring issue may be pulling the ref voltage down more than it should.I have to get it back running first and I am waiting on a part.

"If I'm not mistaken on all the trucks (99 - 03) glow plugs are ALWAYS cycled on for ~2 minutes regardless of temperature. Can you leave your ignition on for 2 minutes with the manual ground and see if it kicks off? It's on a timer

What you are describing is exactly how mine behaves, it's always switched on but turns off after the allotted time above"

That is what I read to, even if the WTS light is not on but there is no timer that I am aware of, there were timers on some older trucks, maybe the IDI's but it is all PCM on my truck. I know it's not actually getting the ground at anytime because I have put a meter on it the "ground signal wire from the pcm nothing!

I will say that I didn't probably go far enough with scans, I mostly looks at temps and pressure's, not so for much voltages which will be on my list.

 

The PCM is the timer. What I'm suggesting is rig up a ground and be done with it. Probe the power lead on the gpr after 2 minutes and I guarantee the power will be off. There's another issue at hand here, my 99 with 303k will start with the glow plugs unplugged at 50 degrees. Does your truck crank slow? If it does then they may be weak. You'd be surprised how much a new battery makes a difference in starting. There's really no need to check all these sensors and spend time on the glow plugs when that's not the main issue.

 

Reference voltage out of wack would not be unheard of. A few years ago there was a truck with a shorted sensor that wouldn't start or even communicate with a scanner.

 

Reference voltage lines are usually VERY important.

 

"The PCM is the timer. What I'm suggesting is rig up a ground and be done with it. Probe the power lead on the gpr after 2 minutes and I guarantee the power will be off. There's another issue at hand here, my 99 with 303k will start with the glow plugs unplugged at 50 degrees. Does your truck crank slow? If it does then they may be weak. You'd be surprised how much a new battery makes a difference in starting. There's really no need to check all these sensors and spend time on the glow plugs when that's not the main issue."

I am pretty sure that my trucks 12v supply to the GPR coil is always on when the ignition key is on.The ground side of the coil is connected to terminal 101 of pcm and according to ford literature the pcm is supposed to briefly activate when a start is attempted, just for something like 30 seconds, even if the truck is warmed up. The coil is activated by the ground side. When the EOT is below a certain level the pcm will command the gpr to stay on longer and if the baro is lower than, say, sea level then the on time is extended as that would indicate a potentially harder starting situation due to altitude. But yours may be different as mine is a 97. My batteries are almost new and the starter is new and it spins fast. Yes I agree there could be another issue but I am focusing on fixing the GPR first and when that is done the other issue, if there is one. may fixed in the process. It seems an almost certainty that the pcm and the gpr are not at fault and neither is the 12v suppl to the coil so there must be something in harnesses or sensors that could be causing the pcm not to activate the ground "signal". At least that is the theory I am working on. The truck sat up for a few years and I tried to start it up on the batteries that were in my 6.0 (me being cheap). They were starting my 6.0 ok but were too low for an engine that was asleep. I fried the IDM and the starter failed right after that. So I paid up and got new stuff. I haven't found any other damage from my foolishness yet. When I got a look at the motor top ( it's a van) the GPR was broken open and i don't know when that happened but no fuses were blown.That GPR was new from the last time I drove it a few years back and then the WTS light stayed on what looked to be an appropriate amount of time.

Chattanooga diesel said they had experience on some occasions with the EBP sensor shorting and killing the ref voltage. Ohm checking sort of went against that but not sure till I read all the voltages for all the sensors after i get it running.
If anybody want to deal with a quality shop for IDM and PCM, Jonathon of Diesel Technology of Chattanooga are very helpful.

 

Pretty sure and certain are 2 very different things. I'm a smart guy and there's times where I was pretty sure but I did it to make sure anyway and found out I was wrong. It's a simple test to do and take 5 minutes max. The reason I say this is because if I didnt check and the relay had power for 1 minute I wouldn't know if it shut off in 1 minute and 20 seconds. Let me do some digging around to see what I can find out.

 

Well OK, I'm positive the relay always has 12v power to the coil all the time when the ignition key is on. Further, I am positive that there is no ground supplied to the other coil terminal . And I am positive that the wire from the ground side of the coil has continuity to the pcm terminal and also that wire has no short to ground. Further, the relay will activate whenever I ground the coil terminal, 12v is always there, the ground isn't..
I'm from deep down in Louisiana and its sort of a southern thing of supposed politeness not to go around saying " I'm positive".

 

My "ground signal" lug on the gpr had 12v to it consistantly. Though i had bad gpr's. Wasnt until i tested that "supposant" ground lug, is when i found the problem.
Now, i control the gpr by way of a ground switch. Real easy to rig one up. While your at it, do the gpr-led.

 

Thanks, but as I am so deep into the money I cant let this go. I want the thing to work properly for pride reason and a real reason of I am going to sell it and don't want to explain about a dash switch that's not supposed to be there. But on the other hand that is the backup plan.

 

If all else fails, you could install an accessory timer to supply ground everytime the truck is turned on.

I installed one of these to turn on my dash camera 30 seconds after the truck was started.


Certainly not the right way to do it, but properly functioning GP's are critical for these dinosaurs.

 

Thanks to all that offered assistance on the this problem. The issue is "fixed", well sort of. I unplugged all the sensor that use 5v ref. Then I plugged them back in one by one. When i got to the last one my meter was still showing continuity to ground from the PCM ground signal wire to the GPR. I reinstalled the relay and GPR closed and ran the glow plugs about a minute even though the WTS light went out in about 5-10 seconds.Just like the book says. I hate it when I don't have the satisfaction of running down a problem and fixing it. But I am glad this is done. Thanks again.

 

Glad you got it fixed and thanks for reporting back.

 

Is your "fix" with or without the new Motorcraft GPR installed?