6.4 Cranks with no Start with no codes

I have a 08 6.4 with a H&S minimax Deleted Cats, exhaust filters, Egr etc.. Ran it with a Performance tune, not towing just driving back and forth to work every now and then about 30 miles round trip. Recently while driving home on the Freeway it died and I tried to restart it. It cranked slowly at first but then picked up speed while I gave it throttle to get it running very badly, I moved it about 100 yards off the freeway to a safer place where it died and would not restart.
Mechainic had it for 3 weeks and diagnosed Nothing! so now I have it back at home and Im trying to diagnose the problem myself.

First I checked for codes and set tuner back to Easy tune. No Faults
Then I used Forscan to check for codes again No faults
I tested the crank and Cam sensors and both are working.
I replaced the Fuel Filters and bled the system, first from the schrader valve then from the banjo.
Tested schrader pressure and it was 5psi but the flow is really weak
with Key on engine off the fuel pump runs continuously, it does not shut off after 30 seconds (not sure if that is normal but I think not)
after all that it Still wont start. it doesnt just spin, it does sound like it is trying to start almost sounds like a gas engine trying to start if you put the spark plug wires on all mixed up or timing way off if that sound is familiar to you guys.
when cranking my scanner shows fuel pressure fluctuating rapidly from 0 to 20000 or so and back very erratic.

Questions I have is can the PCV or HPFP fail without giving a code?
Can a faulty fuel Rail pressure sensor cause a no start and also without a code?
Can the Low pressure lift pump somehow still not be supplying enough fuel pressure even though im showing 5psi?

What other sensors could be bad that will cause a no start without a fault code?

I'm leaning toward replacing the Lift pump hoping it is the problem without knowing if it is or not since Im seeing 5psi but that flow is just looking too weak to me. to give you an idea Imagine if i removed the schrader valve the flow will come out of the tube about a 1/4 inch and drop straight down into a 1/8 to 1/16th of an inch stream it doesn't shoot out at all. probably would fill a cup in about 60 seconds or more maybe?

What do you all think?

Comments

  • I'm guessing the lift pump. I put a AirDog- 165 4G on mine with a sump kit on the tank. Using the sump prevents you from having to drop the tank to get to the lines on top of the tank. The AirDog comes preset from the factory at 10psi. The pressure for the factory lift pump is 3 to 8 psi. Do you see any air bubbles in the fuel stream coming into the fuel bowl? If so, I'm wondering if you have a bad hose which is introducing air into the system.

    You don't have any glitter in the fuel filter housing do you? That would indicate an issue with the HPFP. You should be getting codes I would think. FRP codes.

    Also, reload the tune and change to Mild or HD300. The "Easy" tune tries to cycle the EGR valve and you said yours is deleted.
  • Thanks Smokin,
    There is no glitter in the bowl. But I also have bot yet watched it fill up without the filter and cap I'll have to try that. I will also install the tune you recommended I didnt realise that it did that with the egr.
    In the Sump install on the fuel tank. Is there any concern for knocking it loose off road or are you guys protecting it with some sort of skid plate? Do you have any pics of your install?
  • No glitter is good. As for the sump, I made some extensions to move my factory skid plate lower to clear the sump. The factory skid plate bolts up top by the bed so I just added some spacers to drop it about an inch. You don't need a skid plate according to this video!!

    Here is a picture of mine with the skid plate below it.

  • Hahaha! Great video! Looks like a great idea!
    Thanks!
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