Gas spilling out filler neck while driving! 1977 C-10

[Vintage_Phinds]

I've had this 1977 C-10 that spills gas, while driving, from the filler neck even when 3/4 tank full. Is this common on the 1977? I had a 1979 and a 1981 with no issues. Any recommendations?

 

[ASPEC]

If fuel is getting past the fuel cap then you need to replace it with a proper new cap. That year should have a vapor recovery system and the fuel cap should only be vented into the tank when under vacuum, not to atmosphere.

 

[Ricko1966]

Make sure your charcoal cannister under the hood is hooked up correctly.

 

[84-C20]

I'd say both of those things. Both check the fuel cap and the charcoal canister for correct operation.