Originally Posted by rodmodder
My truck was delivered to the shop today for a new FASS fuel pump. I'd like to do the harpoon mod as well, what do I tell the shop, I've never seen inside a super duty's fuel tank to know what I'm talking about.
Here is a pic of the inside of a 2005 fuel tank looking back towards the fill tube and the vent tube:
For the Harpoon mod, you only have to cut the vent tube (it doesn't make any difference if you cut the fill tube or not). You just cut it as close to the top of the tank as you can.
Here's a pic of it completed:
Normally when you fill your tank, as soon as the fuel reaches the vent tube it will cause the nozzle to shut off and you will have to keep clicking the nozzle a little at a time to get more fuel into the tank.
With the Harpoon mod done, the nozzle will not click off until the fuel level reaches the new end of the vent tube, so your tank will now be almost completely full when the nozzle clicks off for the first time
It is about a 3-4 gallon difference!!! And well worth doing.