The pressure relief valve keeps the pressure inside of the fuel tank below a specified maximum. If the fuel tank becomes over-pressurized, the pressure relief valve opens and allows the excess pressure to exit the fuel tank. The pressure relief valve is attached to the vapor hose, located between the fuel tank nipple and the fuel tank rollover valve. The vapor hose leads the over-pressurized air/fuel vapor mixture to the charcoal canister, which stores the vapors for later use.
REMOVAL & INSTALLATION
See Figure 1
The 2.4L, 3.0L and 3.5L Pick-up trucks and Monteros have similar pressure relief valve locations and use the same procedures for removal and installation.
Access to the pressure relief valve is much easier with the fuel tank removed; refer to the procedures for fuel tank removal, found later in this section. However, access to the pressure relief valve may be possible on some models without removing the fuel tank.
- Compress the spring retaining clips holding the vapor return hose and the pressure relief valve-to-fuel tank hose onto the relief valve with a pair of pliers and slide them to the side.
- Work the valve free of both hoses. Make certain to not allow any contaminants (dirt, rust, etc.) into either hose.
- Insert the new pressure relief valve into the hoses, making certain that it is installed in the correct direction (the pressure relief valve will only flow in one direction-refer to the illustration). The inlet side goes toward the fuel tank and the outlet side goes toward the rollover check valve.
- Slide the spring retaining clips up past the nipple bulge of the relief valve and clamp the hoses in place.
See Figure 2
- Attach a clean rubber hose to both sides of the pressure relief valve.
- Blow lightly from the inlet side of the valve and the air should pass through after a slight resistance is felt.
- Blow lightly from the outlet side and the air should not pass through.
- If the valve fails either of these tests, replace it with a new unit.