Thread: Little pcv valve thing on fuel tank

Hey guys. Cleaned my tank in my n14 and replaced all hoses and broke the little pcv valve looking thing on the tank.

A). What is its function?
B). Where does its second side connect to? Mine wasn't connected to anything when I pulled the tank but I saw a little nipple on the chassis that looks like it is for the valve. But why would anything vent into the boot/cabin??

water seperator? not sure.... wait that kinda looks like the piece off my charcoal canister on the g20t... not positive

Found it on ebay. Called a fuel tank check valve. Apparently it lets air escape as you fill fuel, and vice versa.


Brand New Fuel Tank Check Valve 1986 1990 Nissan Sentra 1986 1989 Pulsar NX | eBay

This is the little nipple (top corner) on the chassis that the other hose on the valve connects to. I have no idea where it leads.

probably just a place for it to secure to, it just vents into the open space inside the frame.

That is a one-way check valve which serves one purpose. It lets excess pressure in the fuel tank escape. This is fuel vapor which is covered by emissions regulations, so it is piped directly to the charcoal canister in the engine bay. This is exactly why the charcoal canister is there... To act as a sponge for this fuel vapor, which eventually gets fed back into the intake when conditions are favorable.

When I removed my charcoal canister, I left this little thing in place, so effectively it vents to atmosphere now. It is a good idea to keep this valve, so the tank can vent and nothing inadvertently enters the tank.

And on cars with no charcoal canister? Our local cars never had them. Also does your tube run from the tank to the engine bay?

The plan is definitely to keep it yes. I found one off a b12 at a junkyard. It's identical even with the part number on it. (Btw, this b12 looks a bit rough but if I had time I'd have loved to bing it back to life and build it!)

It will either feed a hardline to the engine bay with the charcoal canister missing, or I guess it could just feed to atmosphere back by the tank.

Yes, the valve has two, short plastic tubes on it. One goes to the tank, the other goes to a fuel hardline right next to the other two fuel hardlines and the hard brake lines too I think. This hardline goes to the engine bay along with the other fuel lines and terminates way down low in the engine bay by the front sub-frame.

On a side note, wondering if its a terrible idea safety wise to weld a nut onto the tank to create a drain hole? Might make it possible to run and drain some more exotic fuel mixtures when its track time.