How to Replace the Fuel Cap on a 2016 Kia Optima (Fix EVAP Leak & Check Engine Light)
Step-by-step instructions with tools, part tips, safety precautions, and what to expect after installation
How to Replace the Fuel Cap on a 2016 Kia Optima (Fix EVAP Leak & Check Engine Light)
Step-by-step instructions with tools, part tips, safety precautions, and what to expect after installation
đź”§ Optima - Fuel Cap Replacement
Replacing the fuel cap on your Optima is a quick job that helps prevent fuel vapor leaks and can fix an EVAP leak issue that may trigger a check engine light. You’ll remove the old cap from the filler neck and install a new cap that seals correctly.
Difficulty Level: Beginner | Estimated Time: 0.1-0.2 hours
⚠️ Safety & Precautions
- ⚠️ Work in a well-ventilated area and keep flames/sparks away from the fuel door.
- ⚠️ Don’t top off the tank after the pump clicks off; it can cause EVAP issues.
- ⚠️ If the engine was just running, avoid touching hot areas near the rear quarter panel.
- 🔋 Battery disconnect is not required for this repair.
đź”§ Required Tools
You'll need the following tools for this repair:
- Nitrile gloves
- Safety glasses
- Flashlight
- Clean shop towel
🔩 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 P.
- Turn the vehicle OFF and remove the key/fob from the cabin area.
- Use a flashlight to look at the fuel filler area so you don’t cross-thread the new cap.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Open the fuel door
- Put on nitrile gloves and safety glasses.
- Open the fuel door (the small exterior door covering the fuel filler neck).
Step 2: Remove the old fuel cap
- Turn the cap counterclockwise by hand until it releases.
- If your cap is attached to a tether (a small strap/cable), let it hang so it doesn’t scratch paint.
- Use a flashlight to inspect the cap’s rubber seal; cracks or flattening are common failure points.
Step 3: Clean the sealing surface
- Use a clean shop towel to wipe the rim of the filler neck where the cap seals.
- Tip: Don’t use oily cleaners here.
Step 4: Install the new fuel cap
- Align the new cap with the threads on the filler neck.
- Turn clockwise by hand until snug.
- Keep turning until you hear/feel it click (the click means the cap is tight enough to seal).
Step 5: Close the fuel door
- Close the fuel door fully and confirm it sits flush.
âś… After Repair
- Start your Optima and confirm there’s no fuel smell around the fuel door.
- If you had a check engine light for an EVAP leak, it may take a few normal drive cycles for the light to turn off on its own after installing a good cap.
- If the light stays on after several trips, the issue may be another EVAP leak (hose, purge valve, or vent valve).
đź’° DIY vs Shop Cost
Shop Cost: $40-$120 (parts + labor/diagnostic)
DIY Cost: $15-$40 (parts only)
You Save: $25-$80 by doing it yourself!
Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.1-0.2 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.

















