Hypothetically, would your truck start if it was 15 degrees out and you only have four working glow plugs, all on the passenger side of the engine. Lets say you let them warm up once for 30 seconds.

 

Mine would not,thats how I found out I had some bad glow plugs!! I cycled them 3 times and it still would not start. I had to plug in the block heater for about 3 hours before it would start. That was at about 25 deg last winter.

 

No

I end use torch to heat block since I was very late for appoint.

If it was me I would get 8 new glow plugs and new GPR for peace mind in winter when you need BADLY.

 

Sounds funny that you only have glow plugs on one side of the engine. Check the harnesses.

 

Not really that uncommon. People change one side then either run out of time or decide it is to much a PITA to finish. The two I ran across both had all driver side GP's working and one had all the right side out, the other had 3 out.

Mine would not start at 35f with the passenger side GP's not working and 1 bad and 1 weak injector on the same side. I'm sure the compression is a little down on mine with 355,000 miles on it, so yours may do better.

 

Ford says these trucks will start without external aid in temps down to -10 degrees. Of course this assumes a properly working glow plug system and anti gel additive in the fuel.
Any lower and the block heater needs to be plugged in or warmed up via some other method.

Based on that info, I would not expect the engine to fire in -15 temps with only 4 working glow plugs.

 

Yea I agree, it would be hard at the very least. Hell, I don't think I could start at those temps either.

 

With good 850+CCA batteries, 5-40 synthetic oil, a good GP relay and all GP's working, I have started my truck at -15 degrees...BUT the OP asked for ~15 degrees (that little squiggly line means "about", not "minus"). I would guess you would have a heck of a time getting it to fire with four dead GP's at 15 degrees.

 

Yeah I agree. I had no problems around 0f with 15w40 dino (it was a little cranky but had no real trouble), but all was working swimmingly. When my GPR went out, it was hard to get her going at 30f.