I'm working on a 96 f350 since it's been getting colder the owner is having starting problems in the morning. If he leaves it plugged in all night he's fine, but when he doesn't it takes a few tries but it will lite. Last night was very cold and the frost tripped his GFI and could not get it to start. So I came up and his hpop was empty, filled it up and she fired. Runs fine, never stalls. The motor has a reman hpop installed. I don't know if I should be chasing a bad check valve, injector o ring, or ipr. Will appreciate any pointers

 

Here is a thread that addresses that problem.

https://www.ford-trucks.com/forums/1...main-sump.html

 

That was a good read, thank you. My own truck has a similar issue, I've dealt with it but maybe this will inspire me to get mine right

 

I had a hpop draining issue when I bought my truck. My buddy had replaced the lpop and I was at my wits end. It turned out somebody LONG ago had put an early hpop gasket on and it was my issue.
As it has had a pump I bet either gasket or pump are incorrect.

 

If the HPO reservoir was drained, it wouldn't have started plugged up or not. If it won't start unless it is plugged in, then there is another issue with glow plugs or relay.

 

Or a weak lpop that can't pump the cold oil...

 

Or multiple issues....on second thought just give me the address I'll get that heap out of the way lol

 

Possible I guess......

 

Glow plug issues was my first thought until I knew the reservoir was draining. My logic was with it plugged in the oil would stay thinner allowing it to overcome the lower reservoir, and if it didnt fire right off it completely drained and didn't stand a chance. It's got me thinking lpop. And there is definitely a good chance it had the wrong gasket, previous owner was a bit of a yo yo

 

Mine would fire for a second twice then would have filled enough to run

 

Gotta throw a wrench in here. Typically a weak pump is weak, because the of wear increasing tolerances. In that case the pump will have higher bypass, thus less pump output, as the oil thins. The HPOP I believe is a piston pump, the LPOP, I would just guess is a gear pump. Either way, colder (higher viscosity) oil would have more difficulty finding it's way through the internals of a worn pump.

*Disclaimer: This is a general statement made from my experience in hydraulic systems, and is not specific to these components or systems.

 

I took the truck home with me and after sitting over night the reservoir is not drained at all really, got me really thinking a lpop / glow plug issue

 

I also want to add that starting even when it's up to temp it takes a little longer to lite than it should. Also once it fires cold the volt gage bounces for maybe 30 seconds

 

Define bounces? The voltage gauge should go down during glow plug ON time then come back up when the relay disengages. On my truck I get about 11.9 volts with GPR ON and 14.6 volts with GPR OFF, according to my scanner.

Also I've heard excessive cranking can cause the reservoir to drain, but have not experienced that problem personally.

 

Still sounds like GPR and glow plug problem to me. Jim is right about excessive cranking draining the HPO res. If it would only start when plugged in, and the GFI tripped and it wouldn't start, probably drained it cranking. I would check the voltage drop on the GPR and test the glow plugs before I went tearing into the oil system.