GAS CAP

[texasmike]

i have finally got my truck running fairly well and am now waiting my turn at the body/paint shop of my choice. I am not driving the truck very much but I noticed that when I filled up the gas tank, there was a lot of pressure released when I removed the cap. It has the original cap and has had all of the pollution junk removed, including the canister. The gas vapor line to the fuel tank is capped off.

Should it be building up pressure like this and would that hurt anything? It doesn't seem to affect the trucks performance. Everything else under the hood is stock and original.

 

[Frankenchevy]

Get a vented cap. The stuff you removed was vented to the atmosphere.

I’m sure as the weather heats up more, it’ll become more pressurized. May or may not be an issue for your carb.

Your fuel tank is still vented right?

 

[texasmike]

Thanks for the reply Jeremy. The cap is original but I had bought another cap which has a locking feature for my model and it also builds up pressure.

There are three lines at the tank, one is the feed line, one is a return line from the bottom of the fuel pump and the last one was from the removed canister back to the tank. This line now has a rubber cap over the end so maybe the tank is not vented?? If I remove the cap, would it be dangerous for fuel vapors to be released into the engine bay?

 

[Dutch Rutter]

When the charcoal can is removed from these trucks its best to leave the house connected to the tanks but put a one way valve on the end of the hose which would have plugged into the can. Letting things vent into the engine bay is the normal practice.

However, with yours capped there is an easier solution, which wont vent the fumes into the engine bay. Most gas caps say they are vented but, just like a radiator cap, they hold a certain amount of pressure. On older cars and trucks, especially hot rods, with evap things removed, people will drill a very small hole in the center of their gas cap internal plastic (not the through the whole thing just the first layer) to vent the tank pressure.

 

[texasmike]

I pulled the rubber cap off of the end of the steel line in the engine bay with the intention of leaving it off until the paint work is complete and then put the canister back and reconnect the line. However, the fuel smell was so strong that I replaced the cap. It just doesn't seem like a good idea to have those raw vapors in the engine compartment and risk the chance of a fire. Maybe I'm being overly cautious.