I need to know if the charcoal canister for my gas tank is bad. when i run my truck for a while and then unscrew the gas cap i get a loud suction sound, is there supposed to be presure in the tank when the gas cap is unscrewed, i replaced the gas cap and it didn`t make any difference. I removed the large hose thats on top of the charcoal canister and tried to blow air into the canister and it was very very hard to blow air through the canister, does that mean its plugged ?, if so, were can i get a new one ?, any idea how much ?.

 

pressure in the tank is normal, thats why it says on gas caps: unscrew slowly because there may be pressure.

 

I never noticed that the gas cap said that, but is the charcoal canister supposed to be very hard if not impossible to blow air through ?.

 

Technicians use an air hose to test the flow of the c. canister. I'm guessing it must be pretty hard to blow through with your mouth. Just a guess though.

 

The Factory Service Manual has testing and cleaning procedures for the cannister.