Fuel cap question

When open my fuel cap it’s under a lot of pressure; would drilling an 1/8” hole in the cap make any sense or bad idea?

 

What kind of car and set up
California emissions?
Is all the factory stuff connected?

 

Yes do it, it makes plenty of sense, that's actually vacuum you are experiencing, not pressure. It due to the tank not being vented properly.

 

Whatever your car uses as a vent, whether its in the tank or the cap itself, isn't functioning. It's actually air rushing in when you pull the cap off. Your engine sucks the gas, which causes a vacuum to form in the tank. If you go on a long trip, "vapor lock" can happen if you don't remedy it.

 

I have a vented cap, I have the two hose at the top of the fuel tank with the plastic filter however it leaked fuel, I can suck air in through the vented cap it just doesn’t go out

 

The vented caps are one way. Air in, not out. (allow the vacuum in the tank from fuel demand by the pump to be equalized).

The in tank pressure is relieved to atmosphere via vent line(s) typically at the wheel well area. (or line to canister/engine emissions intake).

Drilling a hole may cause spillage issues when you accelerate or if you park on an incline.

Need to make sure the vent lines are not plugged. Mud daubers love to make nurseries in open, round, tubes.

 

They weren’t plugged new tank and original did the same thing

 

My money is you have wrong cap

 

I had the original cap which is nonvented; earlier today I put the plastic filter back on I’ll see if it leaks when I drive back home

 

Think about it. You have the original cap which is non vented, that is the style you need, non vented. When the cap is on air needs to move in and out of the tank, as fuel is used it needs air. When the car is not in use the temperature change means the vent is still needed to move air in and out of the tank. But the volume of air moving is very low. The white plastic vent came with a foam filter material, when that goes away it allows fuel to slosh out. The foam keeps air moving slowly which normally prevents fuel from leaking. I use a foam lawn mower filter to cut pieces from and insert that into the plastic vent, this works for me. Allows air to move in and out, but slow enough to prevent fuel sloshing out.