So I had similar problems to yours. Got a truck second hand that hadn't been maintained. I changed out the glow plugs as one of the first things because I had challenges starting in cool weather. Long story very short after 18 months of plugging it in and investigating/ finding 3 injectors close to failing buzz test I threw some new injectors on it. Cranks first time every time, even in colder weather. Maybe not what you want to hear - sorry

 

If anybody is still looking at this thread I'm about giving up.
a couple years ago I upgrade to the stancor relay and its still testing good
In the past month ive replaced uvch, glow plugs, shimmed injectors and upgraded battery terminals to military style terminals. I run 5w-40 and the truck won't start with oil Temps below about 35.
hoping I don't need new injectors but i don't know what else it could be. My last idea is a new starter as mines cranking at about 145rpm

When I crank it it blows plenty of white smoke and sometimes after a couple cranks and cycling the injectors again waiting to crank again I hear a loud pop from the exhaust which I'm assuming is glow plugs igniting fuel sitting in the cylinders and 100% of the time it will fire right up after the loud pop

 

Could be a mysteriously unreliable/incomplete/erratic/lost permissive signal from the PCM. The GPR won't ground for a completed circuit without that PCM permissive signal. Mine is in the same boat, as has been with others here in FTE as well.

Simplest solution, if the above is the case, is to remove the PCM permissive wire connection and replace it with a momentary toggle switch in the cab. Then you can toggle the GPR "on" for 15030 seconds before you start, start the engine, and go your merry way. It's the plan I'll be implementing when I find my roundtuit, and will simply continue to plug it in every night for anything below 55°F mornings.

See Post #3 in the thread below for a wiring schematic of a manual switch installation. Sous may even come along with additional insight on that option.
https://www.ford-trucks.com/forums/1...er-pulley.html

 

Seems like a good way to test this theory would be jump the constant hot to the trigger terminal for a minute or two before starting and see how that goes if that fixed my headaches that'd be easy and cheap

 

I hope you mean to jump the 2 large lugs. Jumping the positive post to the trigger wire will fry your PCM since the trigger wire is negative

 

Did not know the trigger terminal was a ground... seems a little odd but yeah jumping the two large posts would be the safest best

 

Yes, the trigger wire is ground. I have a push-button installed in the cab for glow plugs. The circuit for that switch is from trigger post on the relay, to the switch, and from the switch to ground. I did it to extend the life of the glow plugs themselves because the PCM commands them on for a while after the engine starts to help control smoking out of the tailpipe. Good idea for the arctic, but I live in Arizona and used to live in very temperate climate Seattle, WA.

 

If it helps any, and i can't recall if I posted this earlier or not as it has been a while. I replaced all the components and still wasn't getting glow plugs to work. I ended up continuity checking back to the computers and fuse box via the 42 pin plug to see if I had wiring issues. I did have a continuity issue - in fact 2 of them by coincidence. I ended up jumping one wire around the 42 pin plug as the pin was not connecting properly. The second issue involved the copper core having rotted out inside the shielding. The wire looked fine but it wasn't until I pulled on it a bit to see something else hat I noticed it had no strength. Cut the sheathing and corroded copper powder came out. It was the last 3 inches to the glow plug relay that was shot.

 

I left my truck unplugged last night I'm about to go outside and try jumping the relay but the only thing that makes me think that my glowplugs are actually getting power and working is that my voltage drops when my glowplugs should be on. That makes sense right?

 

So I went out this morning and my batteries were dead for some reason (think I might have ruined then with all the cold start attempts I've been doing the past month but I connected it to another vehicle let it charge up and shorted the gpr and still nothing. And if I tried jumping g the gpr while the wait to.start light was on I got no sparks pr anything which tells me it was already getting power as it should... I'm stumped now. I have no idea what else to do. It'll even sound like it's firing on a couple cylinder when I'm trying to start it but the second I stop cranking it dies out.

 

Alright put some new batteries in went out this morning and the oil temp was at 13 degrees (outside temp of 15) waited to.crank till after the glowplugs turned off (actually turned off not wts light) cranked it hard for a minute nothing. Cranked again and almost started (idled rough as hell for about 15 seconds before it died) then cycled the glow plugs again. Heard that pop like i described before and immediately cranked again before the glowplugs stopped and she fired right up. Now this startup procedure was done with my tuner on the race mode as it's always most willing to start in the cold with the most aggressive tune. I'll probably try it again tomorrow in stock.

So I'm pretty happy with these results at least I know if I'm in a position where I can't plug her in shell still start. My question now is does this sound like a typical start when it got down to 7 degrees last night and oil temp was 13 or is there still more I can do to help her start well? My next thought is an upgraded starter (either 6.7 starter or aftermarket high torque starter)

 

Also does anybody know what that pop I hear is and why it'll fire up right after every single time

 

I don't know about "normal" , but with mine when it was zero and single digits for a week this winter, my volts take the hit as soon as the WTS comes on, i count 15-20 seconds after the WTS goes out, and crank, usually within 1 second it's lit and running on its own.


As to your pop, it sounds like your injectors maybe aren't firing fuel at first and when it pops that's after they have finally fired, but that's just a guess.

What's your HPOP reservoir level before you crank?

Are you getting a large amount of a white smoke from tailpipe while cranking?

 

I am getting a bunch of smoke which makes me think I'm getting fuel. And how do I check my hpop level? Are you asking how much oil is actually in the hpop? But yeah ideally I'd like my truck to start like that...

 

A lot of white smoke while cranking indicates fuel. Makes me think your glow plugs aren't getting full power, possibly the GPR is making partial contact and once you cycle it again it makes good contact and ignites the fuel mist in cylinder, giving you the pop sound. Or possibly 1 or 2 glow plugs are all that are good. How big of a volt drop do you get when you cycle them? A full volt + ? Or a ⅓ or ½ volt?