Engine/Transmission (1998.5 - 2002) fuel pressure gets erratic below a 1/4 of a tank

[AWeiman]

when a get down to a 1/4 tank of fuel my fuel pressure starts bouncing around between 12-19 psi. it normally runs a steady 15-16psi. then if i let it get down to an 1/8 of a tank i will be driving down the road and pressure will drop to 2 or 3 psi. i orginally thought it was the sending unit and i was just running my tank empty, but after 4 or 5 fillups, i am only gettting 25, 26 gallons of fuel in so i am not running the tank empty. once the tank is full pressure goes back to normal and every thing is fine. any thoughts? it would be nice to have an idea what we are dealing with before we go dropping the tank.

 

[fox]

Your fuel canister is running dry because the screen in the bottom is plugged up. Drill 3-4 1/4 holes around it about 1-2 inches up from the bottom and see if it changes it.

 

[Vaughn MacKenzie]

Or you could have a split or leak in a line inside the tank. It sounds like it's time to drop the tank. If you don't have a canopy, tool box, 5th wheel hitch or other stuff in the bed it may be easier to unbolt the bed and slide it back. Just need to take off the rear bumper first and it helps to remove the back tires. It makes it easier to get at things especially to disconnect the fuel lines and sending unit connector.

 

[AWeiman]

my brother was wondering if maybe it was a split line in the tank as well. i think he told me he just got done working on a truck that had that problem. we'll get into the tank as soon as we get a chance. thanks

 

[JLandry]

Adam,



You might consider installing a Draw Straw I into the fuel module from Vulcan Diesel Performance to eliminate this and any future fuel pickup problems. If you decide to go that route, do a Google search for some good how-to articles on the installation process. Pay special attention on cutting the Draw Straw long enough so it contacts the bottom of the tank. One technique to insure that it still has room to draw in fuel when on the bottom of the tank is to cut 2 or 3 notches in the bottom of the straw wall.



Regarding accessing the fuel tank...



When I needed to replace the fuel level sending unit on my tank, I found it relatively easy to drop the tank. Lifting the bed wasn't an easy option for me because my truck has a canopy. I was able to disconnect the fuel lines and wiring harness from the tank by hand. Once you know the trick to diconnecting the fuel line clips, it's easy.



I supported the tank (with about 8 gallons of fuel left in it) using a ratchet strap toward each end. I loosened and removed the metal tank support straps and then I gradually lowered the tank to the ground by alternately loosening the ratchet straps. Installation was the reverse. I magaged to do do the whole job all by myself out in the driveway in an afternoon. In other words, it's not difficult.



Please let us know how it turns out.



John L.

 

[AWeiman]

john,

if i was reading correctly on vulcan's site, with my fass pump i dont need any extra parts besides the draw straw?

thanks

 

[JLandry]

john,

if i was reading correctly on vulcan's site, with my fass pump i dont need any extra parts besides the draw straw?

thanks

That's my understanding also.



When buying a Draw Straw I, the only choices you need to worry about are the sizes and types of fuel line fittings provided in the kit. Vulcan has a Draw Straw I configuration page so you can choose exactly what you want. While I'm not familiar with the FASS setup, I presume you'll be using aftermarket flexible rubber fuel lines between the FASS assembly and the Draw Straw I... correct? If so, you'll want to choose "Push-Loc" fittings on the Draw Straw. Those are barbed fittings that grip fuel line VERY tightly without the need for hose clamps.



The "Quick-Connect" fittings Vulcan also offers are compatible with the OEM plastic fuel line connectors if you choose to keep those.



If you're in doubt about what to choose, give Vulcan a call.



Best regards,



John L.

 

[ALepley]

My truck is like that I have the fass 150 with the draw straw. Once I get below a 1/4 tank it sloshes around and psi cuts in and out. So I just fill it up before it gets to a 1/4 tank