Topic: Gas tank mod worked!

[stan98tj]

that was where i first checked jeffy. but on the FAQ it says to cut the filler tube..however in the forum is a thread floating around from 2007 where a member advises not to cut the filler, but rather the vent tube. and then the site i found through a google search apparently does this without cutting anything.

[dwtaylorpdx]

On a 94 you can just pull the fill limiter tube out with a pair
of pliers, but if you do it can allow the fuel to contaminate
the vapor recovery system off road. Cutting the tube off
a couple inches is safer.

The tube enters the tank at about a 45 degree angle,
when the fuel gets to it the gas nozzle on the pump
turns off due to back pressure. By shortening the
tube the fuel gets higher in the tank before this
happens. If its too short teh fuel can get against the
vent valves and the sender/pump flange which has a
really crappy gasket system so it can leak, or the fuel gets
sucked up the purge lines into the charcoal canister and if it
goes on enough can allow fuel to be sucked into the intake
from the canister which is bad. You also want a small air space
above the fuel so in hot weather if you fill the tanks it does
not expand and push fuel out.



Dave

[Jeffy]

Cutting the filler?  That won't do anything except get rid of the roll over check ball.  The vent tube is what causes the pump to shut off.  I don't see how you can get by without cutting anything.

[dwtaylorpdx]

Funny we must have hit return at the same time...

Dave

[stan98tj]

Cutting the filler?  That won't do anything except get rid of the roll over check ball.  The vent tube is what causes the pump to shut off.  I don't see how you can get by without cutting anything.

maybe im reading it wrong but it says cut the filler tube: "Once access is gained use PVC cutters ir any sharp shears and cut the filler tube as closely to the top as you're willing to go." had me confused, which is why i asked. maybe im reading this wrong or not understanding it. to be clear though, on a TJ, the vent tube is molded to the side of the tank and that is what needs to be cut.

[sharpxmen]

On a 94 you can just pull the fill limiter tube out with a pair
of pliers, but if you do it can allow the fuel to contaminate
the vapor recovery system off road. Cutting the tube off
a couple inches is safer.

The tube enters the tank at about a 45 degree angle,
when the fuel gets to it the gas nozzle on the pump
turns off due to back pressure. By shortening the
tube the fuel gets higher in the tank before this
happens. If its too short teh fuel can get against the
vent valves and the sender/pump flange which has a
really crappy gasket system so it can leak, or the fuel gets
sucked up the purge lines into the charcoal canister and if it
goes on enough can allow fuel to be sucked into the intake
from the canister which is bad. You also want a small air space
above the fuel so in hot weather if you fill the tanks it does
not expand and push fuel out.



Dave

your explanation makes a lot of sense, but this is what i'm thinking

there is no way you will ever be able to fill out the tank fully - there will be pokets of air in there as the top of the tank is not completely flat and the vehicle won't be perfectly level either. there is also a valve that releases pressure to the evap canister, if a small amount of fuel will make it to the tube going to it it will evaporate inside the canister. I'm also thinking that this is only when the vehicle is not running and that the valve won't open when the fuel pump is pushing fuel. And what happens when you have the Jeep parked on an incline, the fuel will make it to the evap line, there's no way to keep it away from there if the tank isn't leveled so that tube going inside the tank won't help in that instance.

[Jeffy]

maybe im reading it wrong but it says cut the filler tube: "Once access is gained use PVC cutters ir any sharp shears and cut the filler tube as closely to the top as you're willing to go." had me confused, which is why i asked. maybe im reading this wrong or not understanding it. to be clear though, on a TJ, the vent tube is molded to the side of the tank and that is what needs to be cut.

You caught a typo.  Look at the pictures.

[smashcoast]

Stan, when you do this look for some Kilby gas tank skid installation instructions online.Maybe 4wd.com or Quadratec.com.

Follow their instructions. Once the tank is dropped you cut the vent tube which is the small tube next to the filler tube.

once you remove the sending unit, just put your hand and arm in side the tank and cut the small tube. The tube should be about 6-8" long.

Then put everything back. I have a 97TJ that was built in march 0f 96. I have seen before where someone said that the tanks did change at some point and it is only a 15 gal tank. Hopefully yours isnt!

[dwtaylorpdx]

your explanation makes a lot of sense, but this is what i'm thinking

there is no way you will ever be able to fill out the tank fully - there will be pokets of air in there as the top of the tank is not completely flat and the vehicle won't be perfectly level either. there is also a valve that releases pressure to the evap canister, if a small amount of fuel will make it to the tube going to it it will evaporate inside the canister. I'm also thinking that this is only when the vehicle is not running and that the valve won't open when the fuel pump is pushing fuel. And what happens when you have the Jeep parked on an incline, the fuel will make it to the evap line, there's no way to keep it away from there if the tank isn't leveled so that tube going inside the tank won't help in that instance.

All I can say is this is how it worked for me,,,,
The top of the tank on mine dishes down about 1" around the pump opening.
The vent pipe is right on top of the tank edge, if you pull the pipe out and fill up,
and if the jeep is just slightly to the right it will really fill the tank.
I pulled mine out initially, and had fuel gushing out any time I filled it in hot weather,
I shortened the tube and put it back in so now I'm getting 20.5 instead of 22 gallons in the tank.
I also had lost of gas odor from the purge system, and fuel dripping from the top of the canister,
I pulled it off and dumped it out, it had about a pint of fuel in it.

It could be really dependent on the actual tank mold, year of the jeep, mounting hardware etc...

Dave

[sharpxmen]

All I can say is this is how it worked for me,,,,
The top of the tank on mine dishes down about 1" around the pump opening.
The vent pipe is right on top of the tank edge, if you pull the pipe out and fill up,
and if the jeep is just slightly to the right it will really fill the tank.
I pulled mine out initially, and had fuel gushing out any time I filled it in hot weather,
I shortened the tube and put it back in so now I'm getting 20.5 instead of 22 gallons in the tank.
I also had lost of gas odor from the purge system, and fuel dripping from the top of the canister,
I pulled it off and dumped it out, it had about a pint of fuel in it.

It could be really dependent on the actual tank mold, year of the jeep, mounting hardware etc...

Dave

since mine is speculation and yours is a fact i would leave a bit of a tube in the tank then if I would do the mod - how long inside the tank you cut yours?

[FourbangerYJ]

All I can say is this is how it worked for me,,,,
The top of the tank on mine dishes down about 1" around the pump opening.
The vent pipe is right on top of the tank edge, if you pull the pipe out and fill up,
and if the jeep is just slightly to the right it will really fill the tank.
I pulled mine out initially, and had fuel gushing out any time I filled it in hot weather,
I shortened the tube and put it back in so now I'm getting 20.5 instead of 22 gallons in the tank.
I also had lost of gas odor from the purge system, and fuel dripping from the top of the canister,
I pulled it off and dumped it out, it had about a pint of fuel in it.

It could be really dependent on the actual tank mold, year of the jeep, mounting hardware etc...

Dave

I didn't have any of these issues when I pulled the hose doing the 15 to 20 swap. Every now and again I would have gas burp out when the pump shut off but it was only a little gas, not enough to worry about.

[neale_rs]

When one of my vent lines was missing the tank could be filled all the way if you pumped slowly. This can also happen if your pump gasket is not sealing well.

[Jeffy]

When one of my vent lines was missing the tank could be filled all the way if you pumped slowly. This can also happen if your pump gasket is not sealing well.

That works even if your seals are fine.  Pumping slowly, that is.  It tricks the pump to keep on as there is very little pressure so it won't shut off.

[neale_rs]

It could probably also be done fast with a high pressure stream such that the inflow of gas does not fill the fill tube completely.  In this way, air could come out the same tube as we fill. We could develop the device, patent it, and market it for 4x4 enthusiasts who don't want to mod their tanks.  Make the big bucks!

[FourbangerYJ]

Before I did the mod I would fill a Jerry can when I filled the tank. When I got home I would siphon the extra gas into the tank. Then when I upgrade my GTS I did the 15-20 mod.