Ok Here is the deal... 2008 f450 6.4, egr deleted, dpf deleted, air dog fuel pump, cold air intake, turbo back exhaust, H&S XRT PRO, 4.30 gears with 35" tires so lower rpm. the truck will cut out going down the freeway randomly.. also will not start randomly... never any codes when it does this. It has been doing this off and on. it seems fuel related because when it happens if I change the filters it will tun fin again for a week or so. Last month I put a Air Dog 150 on it and it ran perfectly.. for about 3000 miles and now its back to it again. when it wont start you can re tune it and it will start right back up and run fine. but it will come back unless I mess with the fuel filters? weak HPFP? Fuel bowl regulator bad? Any ideas would be great. Also We have put the truck on a snap on scanner and Fuel pressures are where they should be.

 

When it dies have you been able to visually see if it's getting fuel? So in other words, is the fuel filter dry?

It sounds like at high speed operation it's starving for fuel and airating..

Did you have the scanner on when driving as we'll or just at idle? You may have pressure but no volume....

 

When it dies it just cuts out for a second or two and then its fine kind of like turning off a switch and turning it back on ..

As far as the scanner we drove it with it on for half a hour.

Was wondering what controls the fuel pump? ( the frame mounted one )I wonder if the computer is shutting it off for some reason... its just strange every time I mess with the filters or pump its ok... But i still dont get why it wont start unless I retune it ?

 

On the hpfp there is a pcv and vcv.
Volume control valve and Pressure control valve.

 

OK so on the way to work today it shuts off on the freeway wont start no codes.. re tune it starts right back up runs perfect . is there a way to hook up the air dog to run when the key is on , not thru the original fuel pump wire? i tried to do this last night but the truck wouldn't start.. thru a code fuel pump relay or something so I guess it needs to see it there. So is there a way to fool it ? Today I will get a new fuel filter for the air dog and I will bet it runs fine again for a while??? why ?

 

I think I would start at H&S and see if they have run across this, retuning should have nothing to do with the fuel pump, sounds like maybe a tuner issue to me.

 

Talked with H&S they said not there tuner.. Was not to happy with there response but they were no help other than flat out not the tuner.

 

Well, they got pinched so it doesn't surprise me they were a little short with you. They say after you tune you can run the rruck without the control box, I might give that a try, or even better maybe is going to the h&s forum and posting on there, some of the guys there are pretty sharp whwn it comes to issues, they might have an answer for you.

 

Are you positive there is not a short somewhere? I had a mustang that did very similar behavior, changed the ignition switch and never looked back after that.

It would overheat and short out, pull over and wait to cool it off and then I could re-start it and go. Just a thought. Hope you get it fixed.

 

Well I am not 100 percent sure but pretty close I have checked everything I can think of , But still why when it has a new filter does it go away? Does the pump draw too much and get shut off bad relay? so even if the pump shuts off and runs out of fuel why do I have to retune it to get it going? and it will fire right up first crank after its retuned, so I am thinking it must have fuel.... just very strange

 

My thought was that while you are doing those things, the short would have time to cool off so to speak. Possible a wire is arcing to ground as well. Have you run it at night and watched for anything?

That issue I mentioned earlier was very similar. I would crawl all over the engine compartment looking for bad wires or loose connections, get back in the car and it would start up again. Took a while to trace it back to the ignition switch, but it turned out to be that simple in the end.

It sucks being stuck on the side of the road, that much I know. Hope you find the issue soon.

 

Sounds computer related to me. if you can change the filters and what ever else you said but ALWAYS have to retune it sounds like the tuner or the ecu. The ECU runs everything, so it's tuned and everything is working fine, then it falts, then you do whatever and then retune and the retune puts the ECU back to running.

If you haven't already tried it, the next time it falts try not doing anything but an immediate retune. if it starts right back up then you will know. I had a delay shift in my tranny, the guy rebuilt it and went completly through it and it still had the delay. He finally changed the ECU and it solved it.

 

That might be a thought. What is involved in changing a ECU will it have to go to ford to get programmed ? The only thing is when you change the filters it goes away, and when I put the new pump on it went away also. just real strange how it seems to make it different. The no code issue keeps e thinking that it is electrical though...

 

OK, so I misunderstood you. only sometimes do you have to retune it. Other times you changed filters and later a pump and both those times the truck ran without retuning. Those sound fuel related.

never assume that there aren't two things going on. These trucks are very complex. One problem is causing the no start condition. Another problem is causing it to cut out from time to time. The cutting out sounds fuel related while the no start sounds electrical or tuner related.

When you say it cuts out do you mean it goes totally dead for a few seconds or do you mean it shudders?

 

There are time when it will just cut out for a second or two and other times like someone just turned off the key. and there is NEVER any codes when it does this. And i wonder why no codes and that brings me back to a short or something. but it is really strange if I put new filters in it when it acts up it will totally go away for awhile so that has me a little confused ,, and it also seem to get worse when its colder out side It will also run totally fine when i go somewhere I will shut it off, come back to it say in a few hours and it wont start ??? just really strange