Vacuum in the fuel tank

**rion** · August 4th, 2008 01:12 PM

guys, what is the best way to relieve fuel tank pressure? the pressure is great that the cap cannot be remove if you close the cap tight. even when not tight, when I remove the fuel tank breather pipe, I will hear vacuum.

Both ends of the breather hose seems NOT blocked. because when I tried to blow air to it. I hear air passing either ways in or out.

I already switch the cap from another same ride, but same problem. the other ride seems working fine with the suspected cap.

any solutions?

I read that one solution is to drill hole in the cap. but is it really safe? a fuel singaw from the fuel cap hole seems dangerous.

**fourtheboys96** · August 4th, 2008 03:37 PM

i think your talking about fuel pressure and not vacuum. if that is the case, you don't need to worry because its normal. gasoline is a volatile substance and tends to evaporate resulting to build up of pressure inside the tank.

if i am not mistaken, this pressure helps deliver fuel to the engine.

**rion** · August 4th, 2008 09:49 PM

it's vacuum, its giving me hard time opening the fuel cap once closed shut.

**bambino** · August 4th, 2008 10:33 PM

what's the year model you have?

most OBDII SYSTEMS are equipped with computerized EVAP SYSTEMS and that can only be corrected by using a scanner to properly diagnose it with the aid of smoke machine.

**rion** · August 4th, 2008 11:34 PM

it's old 95'. and it doesn't have OBDII slot unfortunately.

**v6dreamer** · August 5th, 2008 01:57 AM

The breather system is probably plugged. There is a tube from the gas tank to the evap emission canister to control the emmission of VOC (fuel fumes), the canister absorbs the fumes, hydrocarbon and sends liquid gas back to the tank. Check for any plug lines. It also vents excess pressure with greatly reduced VOCs. Somewhere along the line, some thing is blocked.

Warning - the old canister is highly flammable.....so be very careful.

**rion** · August 5th, 2008 05:43 AM

I didn't see or maybe didn't notice a canister. but Both ends of the breather hose seems not blocked. because when I tried to blow air to both ends. I can hear good air flow either ways in or out.

illustrated in this wonderful drawing. "blowed" are colored blue.

10kb

but will do try to look again if there is a canister hidden somewhere. thanks.

**v6dreamer** · August 5th, 2008 07:42 AM

Open hood, usually (sorry dont know what kind of car and model of your car) it will be on the right side of the car (passenger) and at the front in the area to the right side of the radiator. It is an oblong shaped box that has a round cap on it.

To easily identify this, the black round cap on it has 2 lines coming to it, one is the vacuum line and the other is the bleed line. This box is fairly easy to see naka-bolt sa tabi. Palitan mo na baka sira na, check also your "evap bypass soleniod valve" and the "vent control valve" are located under the vehicle, roughly below the left rear seat area. They short out due to corrosion/contamination from water seeping into the valves.