pressure in gas tank

[jimmydean]

Just loaded the truck on trailer and noticed something leaking near the rear tire. It was gas coming out from the neck of the filler hose. Then it started squirting from the top of the tank. I unscrewed the gas cap and air came gushing out. Then all of the leaking stopped.  This has never happened before. 

  Its a 79 brocno with a 460. Any and all help/suggestions would be great!!!  Thanks in advance!   

[camok10]

You have a plugged vent line ever noticed how if you leave gas in a sealed can it makes pressure same concept here the gas started to evaporate and had no were to go and found some were

[Blazin40s]

Time for a fuel cell Jim

[xjs3667]

yep ya got a problem in the evap system somewhere... I know on gm vehicles they had charcoal canisters... Don't know if its the same with ford but if it is and ya got one, check there.

[jimmydean]

Its weird.. I have had this truck for a few years and this is the first time its happened. The vent hose goes from the top of the tank to the top of the filler neck. I checked that and there is no blockage. Stupid question, but would/could a bad gas cap make it do this??

[xjs3667]

Its weird.. I have had this truck for a few years and this is the first time its happened. The vent hose goes from the top of the tank to the top of the filler neck. I checked that and there is no blockage. Stupid question, but would/could a bad gas cap make it do this??

yes it can, the vent tube from the tank goes to filler neck before the cap,  The cap is designed to let air in and out but say your rig flips, it wont let the fuel out,  So it is very well possible its the cap, there pretty cheap so I would actually go that route and see if it fixes it, From what I could find ford don't have a evap system like gm. And my 79 chevy was the same set up as you described,   Mine did the same thing you had happen but no gas was leaking, it ended up splitting the filler neck hose   replaced cap and it was good to go..... Another bad thing is with the excessive pressure, if your not running a regulator on your carb and have a mech. pump, your carb can start leaking

[Eroq]

Its weird.. I have had this truck for a few years and this is the first time its happened. The vent hose goes from the top of the tank to the top of the filler neck. I checked that and there is no blockage. Stupid question, but would/could a bad gas cap make it do this??

yes it can, the vent tube from the tank goes to filler neck before the cap,  The cap is designed to let air in and out but say your rig flips, it wont let the fuel out,  So it is very well possible its the cap, there pretty cheap so I would actually go that route and see if it fixes it, From what I could find ford don't have a evap system like gm. And my 79 chevy was the same set up as you described,   Mine did the same thing you had happen but no gas was leaking, it ended up splitting the filler neck hose   replaced cap and it was good to go..... Another bad thing is with the excessive pressure, if your not running a regulator on your carb and have a mech. pump, your carb can start leaking

x2  try a new cap

[Boggen Joe]

Cluged vent

[old school truck dude]

Needs a new cap and make sure its the vented type

[jimmydean]

Yep. Problem is still there.. i took the cheap and easy route and put on a vented cap. A vented cap lets air in but nothing out?  There is a metal line that goes grom the top of the tank to the emgine compartment that im going to asume was for the charcoal vent canister. The canister has been gone forever. Think maybe that line is clogged? '

[xjs3667]

Yep. Problem is still there.. i took the cheap and easy route and put on a vented cap. A vented cap lets air in but nothing out?  There is a metal line that goes grom the top of the tank to the emgine compartment that im going to asume was for the charcoal vent canister. The canister has been gone forever. Think maybe that line is clogged? '

yep, that lines guna be it there

[jimmydean]

Thinkin I should take that line off from the top of the tank and run a new line for it to vent? I hope I don't have to drop the tank! Lol

[xjs3667]

yep,   you might have to drop tank, idk how fords are   go to the end of your line and suck on it, if your getting a good amount of flow and you will konw from the gas vapors   then its not blocked, just keep cutting it and doing it all the way back to the tank, until your past the blockage. try blowing into it too, you might have gotten a piece of rust or sumthin stuck in it on tank side.

[old school truck dude]

You gotta have either the charcoal canister or one of them roll-over valves whatever ya call them. You really dont want to vent gas vapors to the engine compartment, know what I mean?? And yes, the line is most likely clogged at some point.

[jimmydean]

Sorry I haven't got back to you guys on this! I haven't even had a chance to look into it.

If that line does end up to be plugged (hope it is) dumping fuel vapors in the engine compartment doesn't sound like a good idea! Maybe I can re-run it and have it dump in the tail gate of something ..  ++peaceI will let ya know what i find out!

[old school truck dude]

If you tip over, the gas will pour out of the line and maybe catch on fire.Thats why I said a roll-over valve or somethin. The charcoal canister vents directly in to the intake, so gas cant pour out if truck tips over. This is actually kind of dangerous, fires are easy to start but hard to stop. If the tank is full and its a hot day, the gas can expand and come out that line. Charcoal canister or roll-over valve is the way to go. Canister is best way