OT - Anyone here know cars really well?

**wickedsolo** · 07-23-2012, 10:49 AM

Just curious...I don't drive too often and am able to walk to work, but I recently went to fill up my car and noticed that the automatic stop on the pump kept occurring even though the tank was obviously not full. It looks like there is a clog or something and I've noticed that some of the fuel seems to push back up into the insertion area and there seems to be a little bit of a drip underneath where the tank is suggesting that there is some sort of an issue with backflow or something...

Any ideas? I just dropped some major coin on the car to get some things replaced (radiator, etc) and I'd rather not have to spend a bunch of money on fixing something else. It's not impacting the drive at all and once the fuel is in the tank it's fine. It is more just a head-scratcher and a pain in the ass at the pump.

**JAB1985** · 07-23-2012, 11:03 AM

just curious but is this a gas cap that you can access without being in the car, meaning anybody could open it? Sounds to me like maybe somebody stuffed something into it, especially if you can see a clog. The only other thing i can think of is a clogged or jammed vent which would be an easy fix.

**wickedsolo** · 07-23-2012, 11:04 AM

No, you have to actually unlock it via a button on the dash.

Doing some research on my own and it could be a problem with the evap or the hose that travels from the exterior of the car down into the tank.

**Shas** · 07-23-2012, 01:11 PM

Originally Posted by wickedsolo

it could be a problem with the evap or the hose that travels from the exterior of the car down into the tank.

There is a canister filled with charcoal that allows gas tank vapors to be vented (and this prevents pressure from building up inside the tank as you fill it) without allowing the gassy vapors to flow into the atmosphere. The charcoal traps the vapor and then later allows the fuel to return to the system.

The charcoal can get too soaked and swollen with wet fuel and this prevents the vapors from escaping. That leads to pressure in the tank, which triggers the shut-off as you try to pump fuel into the tank, or causes you to nurse a little fuel at a time to avoid the shut off.

I've heard that if you are constantly topping off the tank after the dispenser shuts off it can lead to soaking/clogging the canister. The part is cheap...not sure about labor. I think it depends on your vehicle and where its located.

It's also possible for the canister to be normal, but the pressure sensor solenoid to go bad.

**JustaslowZ06** · 07-23-2012, 01:12 PM

Originally Posted by wickedsolo

No, you have to actually unlock it via a button on the dash.

Doing some research on my own and it could be a problem with the evap or the hose that travels from the exterior of the car down into the tank.

If its a older car these get clogged sometimes. Other than that drop the tank, and pull the filler tube off. Afternoon of work.

**wickedsolo** · 07-23-2012, 01:19 PM

It's an 05 Volvo S60-R.

**wickedsolo** · 07-23-2012, 01:20 PM

Originally Posted by Shas

There is a canister filled with charcoal that allows gas tank vapors to be vented (and this prevents pressure from building up inside the tank as you fill it) without allowing the gassy vapors to flow into the atmosphere. The charcoal traps the vapor and then later allows the fuel to return to the system.

The charcoal can get too soaked and swollen with wet fuel and this prevents the vapors from escaping. That leads to pressure in the tank, which triggers the shut-off as you try to pump fuel into the tank, or causes you to nurse a little fuel at a time to avoid the shut off.

I've heard that if you are constantly topping off the tank after the dispenser shuts off it can lead to soaking/clogging the canister. The part is cheap...not sure about labor. I think it depends on your vehicle and where its located.

It's also possible for the canister to be normal, but the pressure sensor solenoid to go bad.

I had read that as well.

My mechanic will take a look at it and diagnose the issue without charging me for it, so that's not too bad.

Frankly, I just like working on my cars myself and if it is something simple, which JustaslowZ06 says it could be, then I'd rather try and fix it myself.

I need to get some jacks, haha.