This truck has been very frustrating lately driving down the road after half hour 20 minutes of running it acts like it's running out of fuel just shuts off basically. I have changed the lift pump I have dropped both tanks clean the screens put in a new transfer switch transfer valve put in a new injector pump new filters and new injectors now what

 

First check to make sure you are getting constant flow to the filter head: What to do if no Diesel Fuel is coming out of the Schroeder Valve on a 6.9 / 7.3 IDI ? IDI Online

You might have a kink in the fuel hose or pinched fuel line, that is restricting flow.

Try running your truck from a fuel can if possible.

Then make sure you worked all the air out of the injector lines: How to Crack Injector Lines and Purge Air on a 6.9 / 7.3 IDI Diesel Engine ? IDI Online

Do you happen to have a fuel pressure gauge? That would help determine if you have low pressure once you hit 20 minutes or so.

 

I forgot to say that I installed a tank in the bed and ran a new line to the fuel pump, same result. I am beginning to wonder if it's possible there's something internal to the engine but I don't see how.

 

Does it die like you shut it off, or does it stumble, surge, low power, die? If its just "shutting off" i would guess at a bad wire to the fuel shutoff solenoid, bad connection, or bad solenoid. Also not unheard of for this kind of thing to be from a bad ignition tumbler.

 

Thanks it reminded me..it chugs like and then smooths out feeling like your tank ran out and the period between tank switching. I have had a test light on the solenoid during this and the light stayed on steady...

 

So does it actually die, or just loose power for a moment then smooth itself back out? If is dying out, what does it take to get it to start & run normal again? When it starts acting up does the power surge up like someone stepped on the pedal, or just loose power?

 

yes its like someone is pushing on the accelerator sometimes then loses power and eventually actually quits. cranking over and over it eventually starts then does it again. it will start sometimes with a squirt of ether. Time between trying to start might help also but not consistint

 

A power surge is indicative of air in the system. Mine always does this when I run a tank out, I've found it to be my warning sign that it's about to die if I don't do something quick. Why it takes 20 minutes for that to happen is odd . My first thought is that the tank isn't venting and being sucked into a vacuum causing air to be sucked in at a less than perfect connection somewhere.

 

perhaps ill try driving with the cap off and see but that should have been eliminated when I ran the new tank in the bed with newlines to the lift pump...

 

Sounds like you have most of the bases covered. It's almost certainly fuel delivery or air intrusion problem .

Other things to check, fuel lines fuel line restrictions. Also some can have internal blockage or collapse, I know you put one in the bed, just double check.

Check the fuel return hoses also for restrictions.

Replace the fuel pressuring valve at the top of the IP at the return elbow, little 'check valve' with a glass ball in it. A stanadyne dealer will have one for 15$ dollars, nobody else will know what you're talking about.

Pinch off the injector return soft line to the back of the filter housing if equipped.

What everyone else also said and these things should be able to figure it out.

This problem is annoying I know, a small fuel line kink and return line feedback caused similar problems for me and even burned down an IP from the issue. Keep on it, there's something somewhere holding up that fuel.

 

The return line to the filter is new but I will pinch it off. When I had the bed tank straight to the fuel pump the return was still going to the frame tank and it overflowed. I’m not sure where this check valve is unless it’s right where the return line drains from the “rail” to the tank

 

The pressuring valve looks like a fitting that that screws into the IP and adapts for the fuel return elbow or barb, it's not really a check valve, and it's probably not the problem.. But it could be, so best not to overlook it.

It has a tiny spring loaded glass ball inside that maintains a constant static back pressure that the Injection pump likes, for best operation. Not a wide open unrestricted return, and neither blocking flow to the return.

Again, unlikely.. But worth getting a replacement to eliminate that possibility.

You may also have a bad lift pump, and most likely a restricted incoming fuel line. There is nothing in the engine that can cause this problem, it is a fueling problem.

Or ignition, but also a remote possibility with that.. But do double check, run a hot wire to the solenoid.

 

Put a 'boat' primer bulb in a soft line right before the incoming fuel line to fuel filter..

When it revs up, sputters and dies, look at it, it will be collapsed from the IP pulling, but a restriction in the line, it's easy to see, this way. You at least won't think your crazy.

And while it's sputtering trying to get past the blockage you can coax the bulb back open and start pumping while it's running to get it flowing again.

A member here recommended the primer bulb and it helped me when I had a similar problem at least keep it running when I felt it start, could drop to neutral and rev slowly decel coasting, park brake and coax it going again, I also added a second fuel pump that helped, until I found the problem was ultimately a kinked fuel line, one bad injector, and a return hose feedback. Often it's several things that can be contributing, and you can throw several things back to get it back up and running. Don't be afraid to add auxiliary different clear hoses pumps gauges ect whatever it takes to whip that thang.

 

If it's the check valve/housing pressure fitting it will slowly die, and never buck or surge, just slowly die until it quits, then after you let it sit it'll start back and do the same thing over.

Definitely sounds like it's sucking air, my guess is either the olives on the hard fuel lines or your filter housing

 

I’m in the middle of trying all these great suggestions. I will let you know how it comes out. I am also looking at an 08 with a blown 6.4 and a donor 11 with a 6.7....I’m not sure I will like the reliability of the 6.7 especially if I go back to jet fuel