Gas tank venting

[Jarvis-69 GMC 1500CK]

New to old vehichles (oldest before this is a 91 Cadi).

When ever I open up the gas cap (cab mounted behind the seat) Allotof pressure is released, and I notice it seems to affect my gas gauge unless I vent it every day. Is this a normal thing to happen?

[leftybass209]

Originally Posted by Jarvis-69 GMC 1500CK

New to old vehichles (oldest before this is a 91 Cadi).

When ever I open up the gas cap (cab mounted behind the seat) Allotof pressure is released, and I notice it seems to affect my gas gauge unless I vent it every day. Is this a normal thing to happen?

No, that shouldn't happen. It happens because of 2 reasons....

A. You don't have a vented fuel cap

B. You have a new vented fuel cap, and the spring pressure inside the cap is too strong for the tank pressure to overcome.

I had the second issue. New cap, but still wouldn't vent. Actually, it caused fuel to leak from the fuel line where it meets the sender. Had I, a full interior, everything would have been saturated with fuel smell, because it took me 2 days to figure it out. The cab smelled for 2 weeks afterward.

If you don't have a new vented fuel cap, you'll need to get one. Most likely if it doesn't fix your problem, you'll need to disassemble the fuel cap, and clip a little bit of the spring, much like the low budget way of cutting coils to lower a vehicle. Reassemble, and it should be fine.

Best of luck!

[Jarvis-69 GMC 1500CK]

I will probably just get a new locking one. The one I have now does not lock which is....stupid to say the least.

Any recommendations on vented/locking cap?

I dont really care about the looks at this poin, its a rough around the edges daily driver (for now).

[cdowns]

vented or non vented cap depends on the year you have cause they are different

[Jarvis-69 GMC 1500CK]

Its in the name, 69 GMC 1500, and IDK if the cap is factory, not much in this truck is anymore from prev owners. Tranny and engine and interior paint (even seats) are all from other years.

[71threequarterton]

I just noticed the same thing on my 71 C20. I just filled it up Saturday and got in Monday morning to drive to work and the cab smells like a molotov cocktail I've never noticed this before today.

[AnotherWs6]

Good point about the spring leftybass209. I have a new vented cap but it still builds some pressure. Nothing like the NON vented cap I put on a few months ago. I am going to take a look at and see if I can get the spring a little softer.

[dmjlambert]

This is the one I purchased with and was recommended to go with my new tank from Classic Industries, Stant 10491:
http://www.classicindustries.com/pro...s/st10491.html

I wanted a locking gas cap because the filler neck is at the perfect height and plainly visible to entice any 10-year-old kid to mess with.

This one appears to be adequately vented. There was another thread a while back where somebody said when the tank is filled up all the way, some gas will dribble out during turns. This happens with mine. I wonder if there is a better locking and vented cap.

[Jarvis-69 GMC 1500CK]

Originally Posted by dmjlambert

There was another thread a while back where somebody said when the tank is filled up all the way, some gas will dribble out during turns. This happens with mine. I wonder if there is a better locking and vented cap.

My tank is never full enough to worry about it

[AnotherWs6]

I used this one. Looks pretty good, cheap and is vented. It allows some pressure to build up but is minimal and I think normal. Been running for a couple of months through a hot summer, no issues. Just a small amount of pressure release when I go to fill up.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1