Fuel System Question

[1972BlueC20]

I have a 1972 3/4 ton C20. There is no charcoal canister. The gas tank has only 1 main solid filler neck. The sending unit has one large hose and one smaller hose both running to the fuel pump and each hose goes into the pump at their own seperate inlets.

I recently replaced my fuel cap with the one the stant website called for #10623. It was identical to the one that was already on the truck when I bought it.

My question is, did my truck come from the factory with a charcoal cannister? Should I have a vented cap or not? Searching posts on this forum, has people saying mostly that a vented cap is needed. But there are a handful of people saying I should use a non vented. I went with the majority and what stant said on their site and got the 10623 vented cap. Is this correct or not???

[1972BlueC20]

Here is pics of my gas cap

[1972BlueC20]

Anyone?

[CST10]

I thought the 71-72's were vented but not sure. You should be able to see if there is a vent in the inside of the cab. It would be off of the filler neck area and go to the underside outside the cab.

[Lattimer]

C-20's and C-30's were exempt from the emissions stuff, so no charcoal canister. So you need the vented cap.

[davepl]

I can't say for sure about 72, but in 70 they are non vented and no cannister IFF they're a heavy duty unit (3/4 ton or better).