How to Replace the Fuel Cap on a 2018 GMC Yukon (Fix EVAP Leak & Check Engine Light)
Step-by-step fuel cap replacement with required tools/parts, safety tips, and EVAP sealing checks
How to Replace the Fuel Cap on a 2018 GMC Yukon (Fix EVAP Leak & Check Engine Light)
Step-by-step fuel cap replacement with required tools/parts, safety tips, and EVAP sealing checks
đź”§ Yukon - Fuel Cap Replacement
Replacing the fuel cap on your Yukon is a quick job that helps the EVAP system seal the fuel tank. A bad cap can cause a fuel smell and can also trigger a check-engine light (often for an EVAP leak).
Difficulty Level: Beginner | Estimated Time: 0.1-0.3 hours
⚠️ Safety & Precautions
- â›˝ Turn the engine OFF and keep sparks/flames away from the fuel door area.
- 🛑 Don’t replace the cap right after driving if the area is hot; let it cool a few minutes.
- 🧤 Wear gloves to avoid fuel residue on your skin.
đź”§ Required Tools
You'll need the following tools for this repair:
- Nitrile gloves
- Shop towel
- Flashlight
🔩 Required Parts
HowToo sells all the parts you need for this repair:
- Fuel cap (EVAP-sealing type) - Qty: 1
đź“‹ Before You Begin
- Park on level ground and shift to Park.
- Turn the engine off and remove the key/fob from the vehicle.
- Wipe dirt away from the fuel filler area using a shop towel so debris doesn’t fall in.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Open the fuel door
- Press/open the fuel door on the rear quarter panel.
- Use a flashlight if it’s dark so you can see the sealing area.
Step 2: Remove the old fuel cap
- Put on nitrile gloves.
- Turn the cap counterclockwise until it releases, then remove it.
- If your cap is tethered (attached with a small strap), let it hang.
- Listen for cracking or stiff turning.
Step 3: Inspect and clean the sealing surfaces
- Use a shop towel to wipe the filler neck rim (the round surface the cap seals against).
- Check for dirt, rust, or damage that could prevent sealing.
Step 4: Install the new fuel cap
- Place the new cap onto the filler neck.
- Turn it clockwise until it clicks several times and feels fully seated.
- If the new cap includes a tether, attach it the same way as the original (if applicable).
- Clicks = sealed; don’t overtighten beyond that.
Step 5: Close the fuel door
- Close the fuel door firmly until it latches flush.
âś… After Repair
- Start your Yukon and verify there’s no fuel smell near the fuel door.
- If you had a check-engine light from a loose/bad cap, it may take a few normal drive cycles to turn off on its own.
- If the light stays on after a few days of driving, the EVAP issue may be something else (purge valve, vent valve, or a leak).
đź’° DIY vs Shop Cost
Shop Cost: $40-$120 (parts + labor)
DIY Cost: $15-$45 (parts only)
You Save: $25-$75 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.
🎯 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.
















