Fuel tank cap

[smalltruckbigcid]

Is it supposed to vent pressure. My 95 K2500 with a 6.5td builds pressure in the tank. I bought this truck about 2 weeks ago and filled the tank for the first time tonight. I don't drive it much I know. Started the truck from cold (sat for a week) and drove it to the station about 4 miles. When I removed the cap the tank was under pressure. The cap looks like a vented cap. So is the tank supposed to be pressureized during normal operations?
George

 

[joez]

Your tanks not building presure, its creating vacuum. The valves often get stuck, and people like to put gasser caps on them since the partsmonkeys tell them that they are the same. You have a couple options. You can gut the valving out of yours, go buy the correct cap, or simply remove the big O-ring from the cap. Either way take care of it as soon as you can, as that vacuum is putting extra strain on your already problematic lift pump.

 

[smalltruckbigcid]

No its building pressure, as I unscrewed it it popped out into my hand. But by your post I will check on the right fuel cap. I mean just get a new one, thanks
George