If your gas cap won’t click or tighten, it means the cap is not sealing properly against the fuel filler neck. This can cause fuel vapours to escape, reduce fuel efficiency, and trigger the Check Engine Light or EVAP system warning. A faulty or damaged gas cap should be inspected and replaced promptly to maintain fuel system integrity.

What does it mean if the gas cap won’t click or tighten?

Gas caps are designed to click when tightened to ensure a proper seal. If yours doesn’t, it may be worn, damaged, or the filler neck may be faulty. Without a secure seal, the fuel system cannot hold the correct pressure.

Common causes of a gas cap not clicking or tightening

• Worn or damaged gas cap threads
• Cracked or hardened rubber sealing gasket
• Cross-threaded or misaligned cap
• Damaged or corroded fuel filler neck
• Aftermarket cap that doesn’t fit correctly

Why do you need to fix this problem quickly?

A gas cap that won’t tighten properly allows fuel vapours to escape, which reduces efficiency, increases emissions, and can cause the Check Engine Light to turn on. It may also lead to fuel contamination and failed safety or emissions inspections.

How do you know when to get it checked?

You should book an inspection if:

• The gas cap spins but never clicks
• The cap feels loose even when fully tightened
• The Check Engine Light or gas cap warning light is on
• You smell fuel around the car after refuelling
• The gas cap or filler neck shows visible damage

What happens during an assessment?

A mechanic will:

1. Inspect the gas cap for damage to threads, seal, or gasket
2. Check the filler neck for corrosion, cracks, or misalignment
3. Test the seal to confirm if vapours are escaping
4. Replace the gas cap if worn or damaged
5. Recommend filler neck replacement if necessary

How much does it cost to fix?

Gas cap replacement typically costs $50–$120. If the filler neck is damaged and requires replacement, costs may range from $250–$600+ depending on the vehicle.

Is it unsafe to drive with a gas cap that won’t tighten?

While not immediately unsafe, driving with a loose or faulty gas cap can trigger warning lights, reduce fuel efficiency, and increase emissions. It should be repaired or replaced promptly.