Excessive fuel tank pressure..?
09-28-2016, 10:08 AM
#1
Racer
Thread Starter
Excessive fuel tank pressure..?
Car was recently tuned and now I notice that I can not fill the fuel tank after a short drive as there is pressure once I open the cap and the fuel purges out of the tank until the pressure bleeds off in several minutes.
Prior to this tune I never had this issue.. Any suggestions?
Prior to this tune I never had this issue.. Any suggestions?
09-28-2016, 10:23 AM
#2
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St. Jude Donor '15
Doubt it's tune related
There's a little float/vent on the passenger tank that is supposed to close when the passenger tank is full which causes fuel to back up the fill tube. Sounds like that valve is stuck--it's not a totally uncommon issue but not super common either.
There's nothing electrically connected to it, it's totally mechanical, so I don't think the tune is the issue personally unless I'm misunderstanding the problem.
There's a little float/vent on the passenger tank that is supposed to close when the passenger tank is full which causes fuel to back up the fill tube. Sounds like that valve is stuck--it's not a totally uncommon issue but not super common either.
There's nothing electrically connected to it, it's totally mechanical, so I don't think the tune is the issue personally unless I'm misunderstanding the problem.
09-28-2016, 12:42 PM
#5
Racer
Thread Starter
Doubt it's tune related
There's a little float/vent on the passenger tank that is supposed to close when the passenger tank is full which causes fuel to back up the fill tube. Sounds like that valve is stuck--it's not a totally uncommon issue but not super common either.
There's nothing electrically connected to it, it's totally mechanical, so I don't think the tune is the issue personally unless I'm misunderstanding the problem.
There's a little float/vent on the passenger tank that is supposed to close when the passenger tank is full which causes fuel to back up the fill tube. Sounds like that valve is stuck--it's not a totally uncommon issue but not super common either.
There's nothing electrically connected to it, it's totally mechanical, so I don't think the tune is the issue personally unless I'm misunderstanding the problem.
just seems like its not venting, like the evap purge solenoid is off
09-28-2016, 12:52 PM
#7
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St. Jude Donor '15
The evap purge solenoid isn't what vents the tank for filling
And you can't turn that off in the tune regardless--you can unplug it and disable the codes, but that's about it
And you can't turn that off in the tune regardless--you can unplug it and disable the codes, but that's about it
Last edited by schpenxel; 09-28-2016 at 12:52 PM.
09-28-2016, 12:55 PM
#8
Racer
Thread Starter
Yeah I noticed that after looking through Hptuners. Very odd to have that much pressure. Only other think I can think of is the tanks are super-heating and boiling the fuel. Literally took several minutes for the pressure to escape with the fuel cap off.
09-28-2016, 12:58 PM
#9
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St. Jude Donor '15
Did it literally have gas coming out of the cap or fuel just wouldn't go in or what?
There's no way there was enough pressure for it to take minutes to escape through a ~1" hose unless the fuel was literally boiling
There's no way there was enough pressure for it to take minutes to escape through a ~1" hose unless the fuel was literally boiling
Last edited by schpenxel; 09-28-2016 at 12:59 PM.
09-28-2016, 01:01 PM
#10
Racer
Thread Starter
I didnt notice the pressure until I tried to fill the tanks at 3/4 full. The fuel that I was trying to pump in was being shot out of the filler neck and onto the side of the car until the pump turned off.
09-28-2016, 01:04 PM
#11
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St. Jude Donor '15
That's the vent valve I mentioned earlier then more than likely. That isn't pressure from hot fuel or anything like that, it's just the air not having anywhere to go as you add more fuel.
I've had it happen on mine once or twice then it's randomly fine for 6+ months so I've left it alone. Have to drop the passenger tank to change it, which you really don't want to have to do
I've had it happen on mine once or twice then it's randomly fine for 6+ months so I've left it alone. Have to drop the passenger tank to change it, which you really don't want to have to do
Last edited by schpenxel; 09-28-2016 at 01:05 PM.
09-28-2016, 01:09 PM
#12
Racer
Thread Starter
That's the vent valve I mentioned earlier then more than likely. That isn't pressure from hot fuel or anything like that, it's just the air not having anywhere to go as you add more fuel.
I've had it happen on mine once or twice then it's randomly fine for 6+ months so I've left it alone. Have to drop the passenger tank to change it, which you really don't want to have to do
I've had it happen on mine once or twice then it's randomly fine for 6+ months so I've left it alone. Have to drop the passenger tank to change it, which you really don't want to have to do
If I were to drop the tanks that would be a great time to do the Fore setup
09-28-2016, 01:46 PM
#13
Drifting
I back primed everything with an air pistol when my car was doing it after the Eliminator pump install. I also unplugged the solenoid vent in the tunnel. No issues since.
Last edited by chpmnsws6; 09-28-2016 at 01:46 PM.
09-28-2016, 02:24 PM
#14
Team Owner
Ever overfilled the car? Ever "topped off" after pump clicked? If so that is a common symptom. You land up filling the charcoal canister and vent tubes with gas, so they can't vent properly and then can't fill tanks properly.
09-28-2016, 04:21 PM
#15
Long shot (also if I understand your concern properly too)
Has this occurred only once? Have you tried another gas pump? As the tank is filling the fuel delivery system should remove the vapors from YOUR tank, putting them in the gas stations tank, to prevent *fumes* from escaping to the atmos. If that system is not operating properly, slight pressure could theoretically build up in your tank.
Has this occurred only once? Have you tried another gas pump? As the tank is filling the fuel delivery system should remove the vapors from YOUR tank, putting them in the gas stations tank, to prevent *fumes* from escaping to the atmos. If that system is not operating properly, slight pressure could theoretically build up in your tank.
09-28-2016, 07:54 PM
#16
Pro
If I remember correctly, there is a vent canister on the pass side on the frame rail above where the exhaust goes up over the axle. If that is damaged or not working, it will not relieve pressure. I remember dealing with issues like this 2 or 10 fuel systems ago.
09-28-2016, 08:12 PM
#17
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St. Jude Donor '15
On the right side, the sender module contains a secondary fuel pressure regulator ( G ) and a siphon jet pump ( H ). There is also a fill limiting vent valve (FLVV) ( J ).
Operation
When the fuel tanks are filled, fuel first fills the left tank. As the fuel rises to the level of the crossover ( K ), fuel flows into the right tank. As fuel occupies the interconnected tanks, air is forced to vent from the tanks, through the FLVV in the right tank. When both tanks are full, the FLVV float in the right tank closes, preventing fuel from entering the vent system. This also causes fuel to back up in the fill hose, causing the gas pump nozzle to shut off.
Operation
When the fuel tanks are filled, fuel first fills the left tank. As the fuel rises to the level of the crossover ( K ), fuel flows into the right tank. As fuel occupies the interconnected tanks, air is forced to vent from the tanks, through the FLVV in the right tank. When both tanks are full, the FLVV float in the right tank closes, preventing fuel from entering the vent system. This also causes fuel to back up in the fill hose, causing the gas pump nozzle to shut off.
Last edited by schpenxel; 09-28-2016 at 08:12 PM.
09-29-2016, 06:44 AM
#18
Racer
Thread Starter
I had a few minutes to look over the system, just as I thought it was the evap purge solenoid. The harness was disconnected, plugged it back in and back to normal. Thanks for everyone's reply.
09-29-2016, 08:13 AM
#19
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St. Jude Donor '15
That isn't how it works--evap solenoid is closed when the engine is off regardless.
09-29-2016, 08:16 AM
#20
Racer
Thread Starter