05 6.0 Hot Start Problem

[LoCo]

Hey Folks,

I'm trying to help a friend diagnose a problem with his 2005 F250. I've found lots of threads on problems that are close but nothing that quite fits, so bear with me please!

The truck has around 130,000 on it and is bone stock. It starts and runs fine when cold, however, once warm it becomes difficult to start. Once you shut it down, if you immediately try to restart, it comes right to life. If you let it sit for a few minutes it'll crank longer than normal (5-10 seconds) then it'll fire and chug along at 300 - 500 rpm then stall. After 3 or 4 tries it will work it's way up to idle speed and stay running.

So the first question would be, since it does fire (somewhat) does that eliminate the HPOP system as the problem? We were initially thinking leaking dummy plug oring or STC, but since it stumbles along the ICP is seeing enough pressure, is that right? Obviously I don't have access to a scanner just yet or I'd check the voltage and not be bothering all of you!

So assuming that theory is remotely close to being right, where does that leave us? What else could cause this condition? Fuel Pressure, Glow Plugs, UVC Harness problems?

Please Help!!

Thanks!!

[Big Angry Hillbilly]

the longer it sits, the more oil is leaking out of the hp oil system...maybe a dummy plug or something. Or maybe a heat soak on the ICP sensor causing all sorts of issues

[m-chan68]

Originally Posted by LoCo

Obviously I don't have access to a scanner just yet or I'd check the voltage and not be bothering all of you!

Your first course of action IS to have it scanned for DTCs, and if none are retrieved, then it's time to start monitoring some live data (which no ordinary $40 code reader is going to be capable of), and doing some more intrusive tests. Otherwise, you're just pissing in the dark.

Originally Posted by LoCo

So assuming that theory is remotely close to being right, where does that leave us? What else could cause this condition? Fuel Pressure, Glow Plugs, UVC Harness problems?

Yes, fuel pressure (or the lack thereof) can certainly cause what you describe. You state that the vehicle starts up easily when the engine is cold so I would bet money that there's nothing wrong with the glow plug(s) or the glow plug control system (which if there were, the "Check Engine" light would remain on solid). 6.0L engines don't have UVC harnesses. You must be confusing that with a 7.3L. A failing FICM can also cause the symptom you are describing. But again, you need to start with scanning it first.

[LoCo]

Thanks M-Chan,

There are no DTCs, atleast none that the Insight is picking up. Once I get to monitoring live data, what am I looking for? I suppose I'm starting with the ICP to verify pressure from the HPOP, but if that's good what would be my next angle of attack?

Basically I'm gonna have to get a good scanner, I was looking at the Craftsman one, which looks like it'll read the data I need it to, just not going to be able to do the test the AE scanner can. So I'm trying to get a path to head down to see what I need to accomplish this.

And you're correct I'm am confusing the UVC harness with the 7.3....I spend entirely too much time on here reading!!

Thanks again for the help, I appreciate it.

[m-chan68]

What are your FICM_L, FICM_M and FICM_V readings indicating? Pay particular attention to FICM_M. If it's dropping to less than 46 volts, the FICM is going south. Optimum FICM_M readings should be between 47.5 to 49 volts. FICM_L and FICM_V should be at or close to battery or system voltage. Also, what is your IPR duty cycle % reading at HOT idle? Should be between 21 to 23%. Any much higher than that indicates a leak in the high pressure oil system. If all readings check out, you need to connect a fuel pressure gauge to the secondary fuel filter housing next to the fuel pressure regulator. There's a 6mm allen plug that can be removed for the purpose of installing fuel pressure gauge. Fuel pressure should read steady at 56 psi and drop to no lower than 45 psi under load.

[LoCo]

Well we finally got around to checking everything yesterday. All voltages were within the specs listed. So no oil leaks for now I guess. We replaced both fuel filters for good measure and checked the EGR Valve. The valve was coked up pretty good, so we cleaned that up real well and so far it's been good. We'll see what happens.

[jlynch799]

if you can put air into the icp and get some wires to the ipr sensor and put battery voltage to it. then listen for leaks. if theres an internal oil leak it wont start.

[Boggsie05]

I had the same thing - It was the hpop o-ring, apparently a common 05' issue

[Big Angry Hillbilly]

If it ain't starting hot you most likely have a high pressure oil leak.

My guess is dummy plugs or STC fitting.