Preasure building up in my Gas tank (72)

[72 Super]

My gas tank in my 72 4x4 keeps building up pressure. Everyday I remove the cap to relieve the pressure. It also has a pretty strong fuel smell when you open the door. I would assume this is venting issue. It has the correct 72 vented tank in it. It doesn't have the original gas cap, Is there a way to tell if the cap is vented versus non-vented?


Thanks,
Ray

[hugger6933]

Sounds like the purge can is plugged up or the vent tube [line is stopped up and it will do that. Is the can not over by the battery box over on the right hand fender or under it ? I just junked out a 71 and remember a purge can over there . That would be a place to start. Or that what I would do since I have had that happen on later trucks and it ended up being related to the purge canister. On the newer ones say the 03 and newer they put the can under the bed at the back and on the 4x4's over here in the mud on the farms they are forced to live in the purge valves get stuck easily and then the truck is very hard to fill with gas as it takes it really slow. I mean slow like an hour to fil up you can tell the ones with the problems at the gas stations cause they are the ones all mad looking!

[cdowns]

that tank should vent thru the charcoal cannister to the carb// meny guys remove them and plug up the lines causing that problem with the venting and pressure buildup

check that u have the vent line from the tank and it runs into a highloop in the passenger side door pillar then down and thru the floor

the 72 trucks came with nonvented gascaps

[68gmsee]

If the vent in yours has been plugged as mentioned above or maybe changed to one without the vent tube, then you need a vented cap.

Here's a pic of mine. The hole in the middle has a spring loaded vent valve. If you have the vent type cap, you can use a small object to test it to make sure it moves up and down.

[DjS71]

I popped a seam in the gas tank because some genius before me put some plugs in the canister lines and left everything connected for smog appearance. I bought the right gas cap because I didn't have a key to the one that was on there. Pressure.... pop. Gas in the cab. Its something I'll always check for in the future. So either go through the system, or get a vented cap. Just do either one soon, you don't want to have to pull your seat-> tank and get it repaired and soak up gas from the interior... I was fortunate enough just to have bare floors at the time.