Fox T-Bird/Cougar Forums

General => General Fox T-Bird/Cougar Discussion => Topic started by: Ramos617 on January 03, 2014, 10:30:16 PM

Title: Pressure building up inside gas tank, bad?
Post by: Ramos617 on January 03, 2014, 10:30:16 PM
About a couple months ago I upgraded my fuel pump to a 255 walbro from jds
Idk if it really happened before then but I've noticed that pretty much everytime I go to put gas in my tank there is a ton of pressure in my gas tank
If I just unscrew the gas cap a little and let it hiss out it is completely done after about 15-25 seconds but I usually just take the gas cap all the way off and let it gush out

Is this bad or should I just leave it?
My car is running tip top currently with about 197,xxx on the clock, just wondering if it happens to anybody else
Title: Pressure building up inside gas tank, bad?
Post by: STANG8U on January 03, 2014, 10:36:27 PM
Sounds like the evap line might have got crushed during the install
Title: Pressure building up inside gas tank, bad?
Post by: Ramos617 on January 04, 2014, 12:25:27 AM
Where are these evap lines usually located?
Title: Pressure building up inside gas tank, bad?
Post by: flylear45 on January 04, 2014, 06:25:24 PM
It's not venting. Check that the carbon canister isn't plugged up then go after the lines like was suggested. The canister is easy to check before you go through dropping the tank back down to get to the lines. Chances are that's what you'll be doing.

Pull the line off the canister that leads back to the tank and see if your problem goes away. There is a check valve on the tank, so blowing back won't tell you anything, unfortunately. If you have a vacuum tool you can hook it to the line to see if you can get free air flow from the tank. If it draws a vacuum with the fuel cap off the line is crushed.
Title: Pressure building up inside gas tank, bad?
Post by: jcassity on January 04, 2014, 09:59:56 PM
i have to chase down this issue on my 20th as well,, for now i leave the cap a tad bit loose.
Title: Pressure building up inside gas tank, bad?
Post by: TurboCoupe50 on January 05, 2014, 12:12:52 AM
Question...

If the tank can't vent and fuel pump is pumping fuel out of the tank, how can it build up pressure??? Removing fuel will create a vacuum and possibly collapse tank(that I have witnessed with mechanical pumps)... I can see pressure building with high fuel level and high ambient temp but again as fuel level drops so would pressure...

Sooo I'm askin', are you guys sure it's pressure and not vacuum???
Title: Pressure building up inside gas tank, bad?
Post by: STANG8U on January 05, 2014, 12:20:27 AM
I've only had a pressure problem once and that's because I was running open lers and it was heating the tank lol
Title: Pressure building up inside gas tank, bad?
Post by: Ramos617 on January 05, 2014, 02:48:04 AM
It's definitely pressure
I can feel the gas vapors blow by my hand as I unscrew the gas cap
I don't recall coming into contact with any lines that could have been crushed when I replaced my fuel pump so I don't know

I also wanted to note that I am running a k&n air filter so any tubes from the stock air box that were connected to the carbon canister are now not attached