Recently, I've experienced two gas spewage out of my filler neck when I opened the gas cap. It was approx a gallon worth of gas.

The gas tank was not full. First occasion, I had about 80 miles on the gas which would be about 4-5 gallons already gone. Second occasion, filled up tank (stopped when the pump clicked off), it spewed gas out when I opened the gas cap TWO hours AFTER I last drove it.

I asked a few people and they're absolutely mystified. What causes this?

(I think htis is more of a general chat than mechincal)

ive heard of the caps not pressure venting, and causing pressure to build up, but not like that. a gallon!!! idk thats i head scratcher.

my first impression would be that it would have to be something with the evap system letting pressure build up.

could it be evap/vacuum related with the FPR?

i would replace the gas cap to start off if i was you...

Cody, I think that this probably is a mechanical issue and related to your previous mechanical thread where we suggested that you had an evap line problem. It seems obvious to me that one or more of the lines from your gas tank to the evap system is clogged or pinched. You need to find out which one and repair or replace it.

Cody, until you get a new cap, dont just open it right away. Loosen it, let it simmer down, then take the cap off that way you dont lose you highly expensive gasoline.

I know, I asked a moderator where I should put it, it was suggested to put it in Gen. Chat so i did.

And I have replaced the gas cap twice.

If your tank is pressurizing, you have an evap issue. Judging by your other topic, I think it fits.

I suspect your evap solenoid is bad.

The one above the valve cover or the one on the canister?