Fellas -

Has happend twice in the past month. Once just after I filled up, and once right before I filled up. Truck starts running REAL rough at idle, and no better once I'm moving. However, it clears up in a few miles/minutes. Check engine light does not come on.

Seems to not be getting enough fuel - when I stomp on it, it's sluggish and I'm not seeing any black smoke coming out of the tailpipe.

Both times I thought it might be something wrong with the tune, so I plugged in my Bullydawg controller, swapped from Tow/Economy to Performance, etc. Not sure if that fixed it, or if that was just a coincidence that it cleared up after I fooled with the controller.

Any thoughts? Truck has 113k, 7.3, no other mods besides Bullydawg and 6337 filter. It's well maintained and has a fairly new Wix fuel filter, too.

Only thing I can think of is when I run the tank almost dry (when I filled up yesterday, the display said I had only 2 miles left on the tank) that I may be getting some trash in the fuel lines, but the filter should keep anything from getting to the injectors.

Thanks!

Scott

 

Could very well be a fuel problem. Might also be a CPS going out. Contrary to popular belief, they don't always fail like flipping a switch. My first CPS failed over a period of time and the gray one I have in there now is in the process of heading south. Going out to change it now............

 

The fuel pickup foot in the tank may have some garbage in it that is causing it to restrict fuel to the pump on the frame rail. The reason why I say this is because of no CEL light on the dash when this happens and you mentioned that it was after the tank was real low on fuel.

 

Sounds to me like your fuel pump was sucking air and had to get the air out of the system. Takes a few miles to get the air out. Don't let the tank get that low. . lol

 

Check for some water in your fuel bowl by draining a little fuel out. I would consider draining all of the fuel out of the bowl and clean the bottom of it. Some 'crud' builds up at the bottom and some may be sloshing around.

 

That makes sense to me. When it started running rough, I was idling at a stoplight with an empty tank on a decline, so that would have uncovered the pickup.

Thanks!

Scott

 

untill you do the in tank Mod treat the 1/4 mark as if its the empty mark..when you get down to 1/4 tank with no mod's done you run the risk of letting air into the lines.. here is a link to one of many intank mod kits http://www.itpdiesel.com/store.php/products/73L_TankKit

 

I agree, and I'll add that if you keep doing this, you'll eventually clog up the screens in the mixing chamber so that filling it back up won't help you. If you don't do the in tank mods like Ron suggested, then keep it above 1/4 tank. If you don't, just remember in tank mods so when you come back trying to find out about your fuel restriction, you remember what to search for

If you're getting low enough to suck air, do you think your screens look like this


or perhaps closer to this



The bottom pick was dirty enough that the vehicle could not maintain constant speeds on the highway.

 

Could certainly be fuel starvation but...don't get tunnel vision and forget other causes. After an intermittent no-start and die without warning situation a few years back (no codes thrown) I always remember how important the IPR is. A dirty IPR or simply a loose nut on the IPR coil can cause havoc too. The IPR controls if and how that fuel gets into the combustion chamber. It has little bitty holes in it that can clog. I always have a spare with me. Just saying if it turns out you have fuel delivery then look there next. Make sure that cheesy little stamped steel IPR coil nut is tight. AutoEnginuity is your friend to diagnose those types of things.

Edit: re-read your post. Changed filter when last? I have had 2 times now that I got fuel so bad I had to change filters before it should have been due.

 

Thanks for all the input, pictures, etc. Need to keep more fuel in the tank, and in tank mods are on the list of things to do.

Thanks again!

Scott