Gates 31778 Fuel Tank Cap

Gates 31778 Regular Locking Fuel Cap

The Gates 31778 locking fuel cap is a regular threaded fuel tank cap built to meet OEM specifications and emission requirements. It adds a secure, lockable closure for the fuel filler neck while maintaining proper tank breathing through a two-way pressure relief and vacuum relief valve.

Key Features

• Lockable design for added fuel cap security
• Regular fuel cap style with threaded cam type
• Emission control venting to support fuel system sealing
• Two-way pressure relief and vacuum relief valve
• Thread diameter: 1.77 in; shell diameter: 2.91 in; depth: 2.61 in
• Built to Gates fuel cap specifications for direct replacement use

Product Details

This Gates Regular Locking Fuel Cap is a direct replacement for a wide range of vehicles that use a threaded filler neck, including Chevrolet Silverado 2500 HD, GMC Sierra 3500 HD, and Ford F-250 Super Duty applications. The cap is engineered to help maintain the fuel system seal while allowing the tank to breathe as pressure changes, which supports proper evaporative emissions control and consistent fuel delivery system operation. Part number 31778 is also referenced in aftermarket catalogs under cross-reference numbers such as Wix 46340 and Dorman - First Stop 46350 for the same application.

Compatible With 1992-2015 Chevrolet Silverado, GMC Sierra, Ford Super Duty, Jeep Wrangler, Nissan Pickup, and many other listed applications, this fuel tank cap is a practical replacement when the original cap is worn, damaged, or no longer sealing correctly. The Gates 31778 is a straightforward option for drivers servicing older and newer trucks, vans, and passenger vehicles that require a regular locking fuel cap.

Common Problems This Part Can Address

• Fuel cap warning light caused by a poor seal
• Fuel vapor odor from a leaking or loose cap
• Damaged or missing locking fuel cap
• Evaporative emissions system faults related to cap sealing
• Difficulty maintaining proper tank pressure or vacuum balance

Installation Notes and Tips

Verify the filler neck style, thread diameter, and vehicle application before installation. This cap is for threaded filler neck designs and should be checked against the original cap’s dimensions and locking style. After installation, tighten the cap until it seats securely and confirm that the locking function engages properly.

Quality Assurance

Gates states that this locking fuel tank cap meets OEM specifications and Federal and State emission requirements. The integrated two-way relief valve is designed to help the fuel tank breathe while limiting fuel vapor escape.