91 YJ Fuel Pump Noise

[DuneRunnersDad]

Hey guys- I need some help.

After driving on freeway for 30 minutes I hear a loud humming coming from fuel tank. I remove gas tank cap and hear that humming is coming from inside fuel tank. I drive another 30 minutes and check again. This time a HUGE amount of compressed air comes out of the filler neckwhen I remove the cap. It's so much air that I had to depress the trap door in the filler neck to let all the air out.

New fuel pump?
Is there supposed to be a vented fuel cap?
Is there a smog canister that might be plugged?

Thanks, DuneRunnersDad

[gokartergo]

This one might be better answered on pirate.. There is a newbie jeep forum there.. Sorry couldn't help.. Mine is carbed.. So no fuel pump in tank..
http://www.pirate4x4.com/forum/forumdisplay.php?f=67

[DuneRunnersDad]

Thanks Dan. I gave them a try last night on their (Hardcore Tech) area and got one response. Said air pressure was normal. I don't think so. I'll keep trying with the newbie area.

[4X4HIGH]

It is normal to have a vacuum in the tank on hot days but it might be time to replace your gas cap. They are vented and it might be bad not allowing the tank to vent properly causing the excessive amount of vacuum. As far as the load pump goes, might be getting ready to go out on you. Depending on how old it is you might run the tank down low and replace it as preventative maintenence.

[DuneRunnersDad]

Scott- It's original 1991. I've talked to some guys on Pirate who recommend the same. I'm going to change the filter tomorrow and blow out the smog line to the cannister. Jeep sells the pump as a package with the float, sock,wires. Guess I'll get the cap tomorrow and look into pumps when I get back down the hill. Thanks