How to Replace the Fuel Cap on a 2018 GMC Acadia (Fix EVAP Leak & Check Engine Light)
Step-by-step instructions for screw-on vs capless systems, plus tools, parts, and safety tips
How to Replace the Fuel Cap on a 2018 GMC Acadia (Fix EVAP Leak & Check Engine Light)
Step-by-step instructions for screw-on vs capless systems, plus tools, parts, and safety tips
đź”§ Acadia - Fuel Cap Replacement
Replacing the fuel cap is a quick job, but it’s important because a loose or faulty cap can trigger an EVAP leak fault (often a check engine light) and let fuel vapor escape.
Before we start: does your Acadia have a screw-on fuel cap, or a capless filler neck (only a spring-loaded door/flap, no removable cap)?
Difficulty Level: Beginner | Estimated Time: 0.1-0.3 hours
⚠️ Safety & Precautions
- ⚠️ Work outside or in a well-ventilated area; fuel vapors are flammable.
- ⚠️ No smoking, sparks, or open flames near the fuel door.
- ⚠️ Turn the engine OFF and keep the key/fob away from the vehicle while the fuel door is open.
- ⚠️ If fuel was just dispensed, avoid touching any wet fuel; wipe spills immediately.
- Battery disconnect is not required.
đź”§ Required Tools
You'll need the following tools for this repair:
- Nitrile gloves
- Safety glasses
- Clean shop towel
🔩 Required Parts
HowToo sells all the parts you need for this repair:
- Fuel cap (correct type for your Acadia) - Qty: 1
- Fuel cap tether (if damaged) - Qty: 1
đź“‹ Before You Begin
- Park on level ground, shift to Park, and set the parking brake.
- Turn the engine OFF and remove the key/fob from the vehicle area.
- Open the fuel door and use a clean shop towel to wipe dirt from the filler area so nothing falls into the tank.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Open the fuel door
- Open the fuel door by hand.
- Put on nitrile gloves and safety glasses.
Step 2: Identify your filler style (cap vs capless)
- If you see a round cap you can twist off, follow the Screw-on Cap steps below.
- If there is no removable cap and only a spring-loaded flap/door, follow the Capless steps below.
Step 3A: Screw-on Cap — remove the old cap
- Use your hand to turn the cap counterclockwise until it comes off.
- If there’s a tether (a small strap that holds the cap), keep it from twisting up.
- Tip: Don’t drop dirt into the filler neck.
Step 4A: Screw-on Cap — install the new cap
- Use a clean shop towel to wipe the sealing surface around the filler neck.
- Thread the new cap on by hand, turning clockwise until it’s fully seated.
- Keep tightening until you feel/hear the cap click (if your replacement cap is a “click” type).
- Tip: Hand-tight only—no tools.
Step 3B: Capless — what “fuel cap replacement” means
- On a capless system, there usually isn’t a replaceable outer cap; the “cap” function is built into the filler neck (the spring-loaded seal/valve).
- Use a clean shop towel to wipe the area around the flap.
- If your check engine light is on for an EVAP leak, a capless system may need the filler neck seal/valve serviced rather than a cap.
Step 4: Close the fuel door
- Close the fuel door securely by hand.
- Use a clean shop towel to wipe any fingerprints or residue.
âś… After Repair
- Start your Acadia and confirm there’s no “tighten gas cap” style message (if equipped).
- If you were chasing a check engine light, it may take a few normal drive cycles to clear on its own; otherwise, use a scan tool to clear codes and confirm the EVAP monitor passes.
- If you smell fuel after driving, stop and re-check that the cap is fully seated and the sealing area is clean.
đź’° DIY vs Shop Cost
Shop Cost: $60-$150 (parts + labor/diagnostic)
DIY Cost: $15-$45 (parts only)
You Save: $45-$105 by doing it yourself!
Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.2-0.5 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.
















