I harpooned my tank several months ago, great mod. I normally could only put 25 gal in the tank easily, and now put up to 33 in it with one click!

I run it down close to empty with the lie-o-meter at "20 miles to empty" or so. BUT, it seems my gauge has gone stupid. The last two times it got down to "40 miles to empty" with the needle just above E it quickly falls below E. The truck then bucked like out of fuel and took over 33 gal to fill it.

Anybody had similar experience....?

 

Can you explain the purpose of harpooning and a summaryof how it's done?

 

There are two white plastic tubes that go into the fuel tank about 3 - 4 inches. One is the fill tube and one is the vent. If you cut these tubes off about a half inch from the top of the tank (inside) with a pvc cutter your tank will not foam up when you are filling it. You can fill it right to the top of the tank without the usual shutoff from foaming fuel. I guess the tank was made this way to allow for gas expanding. But diesel doesn't expand. I used to fill my tank to about 25 gallons then have to spend 5 - 6 minutes toping it off if I wanted it completely full. Now I fill it right up to 33 gallons. Their is a good thread with great pictures showing how to do it.

Randy

 

Here is the link to the instructions in the tech folder:

https://www.ford-trucks.com/forums/2...-the-tank.html

 

I do not understand the benefits of doing this. Whenever I fill up, the first click from the nozzle....my gauge shows full.

I'm not sure why you guys do this....Any other reasons?

 

More fuel in tank = extended range = less stops for fuel.

 

yet it shows full, but there is enough room for 4-5 gallons more. the vent tube creates a air bubble that gets displaced with additional fuel after doing this mod. plus, as mentioned, the pump now cuts off when the fuel is at the neck. when i did mine, I ran it until empty (around 2 gallons left), and when I filled up was able to put in 33 more gallons. so that "29" gallon tank will hold 34-35 gallons. so, at a conservative 16 MPG, that is an additional 80 miles you can travel between fillups.

 

The only way to get an accurate reading for computing fuel economy is to fill it to the brim. My 38 gallon tank will take another 6-7 gallons after the pump clicks off. I have not done the modification yet so, like someone else mentioned, it takes quite a while to fill to the brim because of the foaming fuel.
I have kept a log book in my truck since it was new. I make an entry every time I go anywhere and mileage at every fuel stop, oil changes, fuel and oil filter changes etc., it is all in there. I have a record of every gallon of fuel that has gone through my truck. This truck was a huge investment for me so I decided that keeping good records was the prudent thing to do. I don't do this with my other vehicles.
I really need to do the harpoon thing on my tank.

 

Got it. So hypothetically, I can accomplish the same exact thing by spending an extra 2-3 minutes SLOWLY (after the first click) filling the tank?????

If so, it seems like alot of work for nothing...Just my opinion....Don't yell at me please

 

Probably a little longer than that, and you won't get the same fuel level every time to make accurate mileage calculations, but yeah.

 

yep. same net effect, if you can actually and accurately get it full. but I did the hutch mod on mine (not sure if it applies to the 6.0), so it only made sense to harpoon it while I dropped the tank. plus, sometimes non-performance mods are just fun things to do.

actually unless i'm mistake, and that is very well likely. the way it looked to me, is that you would NOT be able to get the same amount of fuel in. I THINK the vent will still trap some air inside, but I'm not sure about that. I know that even when i trickled in fuel until it was at the neck, I could never get in as much as i can now that i've harpooned it.

 

i found these here: Harpoon mod (In Tank Mod)

tubes before mod


after


yellow tube is vent. i can't see how, without cutting it, you can get the air out and fill it slam full of fuel. but I ain't no engineer, actually started out as one, but now just an afro-engineer

 

Takes a good while longer then that, its nice to fill it up right full on long trips! When you put a lot of miles on its a nice and worthwhile thing to do. I don't do a huge amount of driving but I will do this when I remember to do it.

 

Yeah I agree. I never really thought of going past the "click"

 

I won't do this mod....just my opinion.....so basically do you guys fill the truck "ALL THE WAY UP TO THE FILLER NECK"?