🔧 MX-5 Miata - Fuel Cap Replacement

Replacing the fuel cap is a quick job that helps keep fuel vapors sealed in the tank. A worn or incorrect cap can trigger an EVAP leak and turn on the check engine light.

Difficulty Level: Beginner | Estimated Time: 0.1-0.2 hours

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⚠️ Safety & Precautions

• 🚫 No smoking or open flames near the fuel door.
• ⛽ Do this with the engine OFF and away from hot exhaust components.
• 🧤 Wear gloves; fuel can irritate skin.
• 🔋 Battery disconnect is not required.

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🔧 Required Tools

You'll need the following tools for this repair:

• Nitrile gloves
• Safety glasses
• Clean shop towel
• Plastic trim tool

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Fuel cap (sealed/EVAP-rated) - Qty: 1
• Fuel cap tether/retainer clip - Qty: 1 (only if damaged)

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📋 Before You Begin

• Park on level ground and shift to Park, then set the parking brake.
• Let the car sit 5 minutes if you just drove it.
• Wipe dirt around the fuel filler area with a clean shop towel so debris doesn’t fall into the filler neck.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Open the fuel door

• Use your hand to open the fuel door.

Step 2: Remove the old fuel cap

• Turn the cap counterclockwise by hand until it comes off.
• If it’s tethered (a small strap that keeps it from getting lost), let it hang.

Step 3: Inspect and clean the sealing surfaces

• Use a clean shop towel to wipe the filler neck sealing surface (the smooth ring the cap seals against).
• Check the old cap’s rubber seal for cracks, flattening, or dirt buildup.
• Tip: Dirt on the seal can cause an EVAP leak.

Step 4: Transfer the tether (if needed)

• If the new cap does not include the tether, gently release the tether/clip using a plastic trim tool.
• Install the tether onto the new cap the same way it was on the old one.
• A plastic trim tool is a non-metal prying tool that helps avoid scratching plastic.

Step 5: Install the new fuel cap

• Thread the cap on by hand clockwise until it seats.
• Keep turning until you feel/hear it click.
• Make sure it’s snug and fully seated; don’t force it past the normal clicking.

Step 6: Close the fuel door

• Close the fuel door securely by hand.

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✅ After Repair

• Start the engine and confirm there’s no fuel smell around the fuel door.
• If you had a check engine light for an EVAP cap issue, it may take a few drive cycles to clear on its own.
• If the light does not clear after a few days of normal driving, the code may need to be cleared with a scan tool and the EVAP system may need further diagnosis.

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💰 DIY vs Shop Cost

Shop Cost: $50-$140 (parts + labor)

DIY Cost: $15-$45 (parts only)

You Save: $35-$95 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.2-0.4 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.