Like many of you I had an issue I could not figure out that plagued me and drove me here. My issue was that my 05 F250 6.0 would shut off like it was out of fuel with around 1/4 tank remaining on the guage. It had done this since I bought it used with 34,000 miles on it. It had left me stranded on the side of the road more time than I want to remember. I would dump a gallon of fuel in and it would start right back up and get me to a gas station. I always crawled under the tank and knocked and I knew there was still fuel in there. So WTF???



After reading some posts I began believing that it was a bad float assembly giving me an incorrect reading. So I tried running techron and everything else the other guys on here were doing before they replaced the entire assembly to the tune of $300 (for the part only).

I had to drop the tank twice before I solved it, but I finally got it. The first time I dropped the tank and pulled the float assembly I checked the float assembly for any corrosion or spot that it stuck throughout the range on movement and found NOTHING. Upon further examination I found one thing that stuck out to me as not being right. The screen assembly at the bottom of the up tube had a gaping hole in the side of it about two inches up. It looked like a fitting where another pipe or valve would fit into. I figured that if something was missing out of that hole it would be sucking air through that hole instead of fuel through the screen.



Figuring that this had to be the issue I called all of the local Garages and asked them if they had a new assembly and if the could describe what fit into the hole. After a solid hour of calling around I found a dealership 3 hours away that had one in stock. The Service Guy there told me that there was an orange valve that fit into that hole and blocked it off. So I went back to my tank and searched with a flash light and could find nothing, I then dumped the fuel out of the tank and still could find nothing so I went to Advance Auto and Bought an assorted set of rubber vacuum line plugs and jammed one in to block the hole.



I ran the truck down to E and when the LOW FUEL signal came on I was so happy I didn't have to replace the $300 float assembly, but I remained puzzled. Where did the little orange valve go??? Was it ever in there??? So a week down the road I read on here about harpooning the tank. I thought that would be an easy mod since I knew dropping the tank wasn't that bad so I dropped it and reached in with my PVC snips and clipped the fill and vent tubes. I pulled them out of the tank and when I did something fell out of the vent tube and it was orange. So I picked it up and looked at the screen boot and thought I WONDER???



Yup!!! That was it, at some point it came loose and got sucked into the vent tube and became lodged. So I stuck her back into the boot, cut the vaccum plug down to size and stuffed it in over top of it so it will never come out again.



I have now ran my tank down to the signal over three tanks of fuel and watched the LOW FUEL signal come on just because I could. Hope this saves someone some $$$$$$

 

do you have to drop the tank to do this? My truck does the same thing.

 

this is why I fill my tank when it gets to 1/2.. just kidding, good find!!

 

I dropped the tank, some other guys say that it is easier to lift the bed if you have alot of fuel left in the thing. Dropping the tank was pretty easy though. I did it once in a garage and once in my back yard with no problems.

There are many posts on dropping the tank in other threads, the easiest way I found is
Run the tank as far down as you can to get rid of some of that weight.
- Remove the rear strap bolt and let the rear of the tank hang. This gives you room to reach on top of the tank.
-Reach around the rear frame rail and find the vent and fill tubes and with either a stubby flat screwdriver or a socket driver loosten the clamps, I forget what the size was but they are regular screw clamps.
-Once they are removed, remove the front tank strap bolt and lower the tank part way so that you can see the top of it.
-On top of the tank you will find the sending unit plug and four more hoses or lines for a total of six.
-The hoses to the front and rear of the tank seem to be some type of venting system and simply pull off. But you will need two different sizes of fuel line removal tools to remove the fuel lines from the float and line assembly. I bought the silver one that looks like an X that has two different sizes with one on each end.
-After you disconnect all of the lines and unplug the sending unit you can drop the tank the rest of the way and pull it out from under the truck.
- Then using a strap wrench or hammer and punch (NOT THE PREFERRED METHOD BUT IT WORKS) remove the plastic ring that holds the assembly in and your set.
- Replace everything in the reverse order.
NOTE: when you are replacing the plastic ring it will seem like it doesn't want to thread on right because it needs to be tapped on over the first lip before it will catch the threads, at first I thought I was crossthreading it until I realized it just wasn't catching the threads. Once it caught though it screwed on and tightened smoothly.

The worst part of the job was disconnecting the fill and vent lines, it was frustrating to try to reach in there and get them. All of the other lines have enough extra to allow you to drop it a little.

This was my way of doing it but there are many other posts on here about dropping the tank. While you have the tank down you might as well harpoon the thing. It makes total fill up alot easier.

 

I must have missed this one the first "go-round" - great post hubler!

 

That's a great post. I ran my tank down to the light last week. didn't have a problem, but am glad to know about this in case! Reps to you!

 

Since I have a lift it sounds like lifting the bed would be easier. Do you agree?

 

This is great information however, you said you used a vacuum plug.
About a year ago I purchased and installed a Titan 50 gal fuel tank. When I installed it, I needed a longer piece of hose for my vent line. I had some lying around in garage so I just used it. After about 6-8 months I noticed fuel would spill on the ground from under my truck when filling up to the limit. After I ran the tank down to empty again I dropped the tank and found the vacuum line hose I used was swollen and disintegrating from the fuel. I knew vacuum line was not rated for fuel but figured for the vent it would be no big deal….. I was wrong.
Long story short, I would recommend you drop your tank again and get the vacuum plug out of the fuel. It will not last in there.
Sorry for being the bearer of bad news.

 

Thanks for that info, that was a concern of mine. The rubber that was used for these plugs was a very thick almost plastic like rubber, not the flimsy hose you would use for vacuum lines. I had addressed my concerns of this by soaking one in diesel fuel in a liter soda bottle for about 2 months. There was no change to the pliability of the plug that I used. But you are very right that care should be given when deciding what to plug it with.

 

If you have a lift I would definately use that, that way you can ensure that you have plenty of room to tighten the hoses. That was the biggest PITA. I am a big guy with big hands and it was a pain to reach up on top of that tank and try to make sure everything was tight.

 

X2 on the rubber plug deteriorating. I would put something else there.

But if you are good with your maintenance, just check your primary fuel filter for pieces of rubber when you change it. The little black pieces should show up easily on the white aquablock of the filter.

 

I posted this about a year and a half and 30,000 miles ago and always do a good visual on my fuel filters and haven't seen any sign of rubber in them. Maybe I got lucky with my choice of material and it hasn't deteriorated on me.

I guess the point of this post was to share the problem I found and how I decided to fix it. I could have pushed the valve back in and just left it, risking that it could pop out of it's groove again. The boot is made of very soft pliable rubber and it was a pain to get anything to stay but the rubber plug I bought stuck in there stayed with no problems, so that's what I used.

A copper 3/4" pipe cap comes to mind as a decent plug.

 

The intent of that valve is to provide fuel if the primary pickup screen gets plugged up. We find this constantly with bio diesel usage. The primary screen will be clogged with "butter". The valve opens still allowing fuel flow (unless the fuel level is below the valve).

 

I was also running out of fuel at the 1/4 tank mark. I found out why last weekend when I pulled the sender unit out to harpoon my tank and found the pick-up strainer assembly in pieces. I bought a piece of 3/8" stainless tubing and a compression coupler and extended the pick-up tube down to 1/4" above the bottom of the tank. I also hose clamped a piece of stainless screen to the bottom of the tube as a pre-filter. So far I've driven 45 miles since the low fuel light came on.

 

The pick up tube is available separately btw. I see them cracked also,, which will cause the exact symptoms. Iirc it's about $30 or so.