How to Check the Fuel Cap Indicator on a 2002 Mercury Mountaineer

The 2002 Mercury Mountaineer came with a 4.0-liter six-cylinder engine and a five-speed automatic transmission. The on-board computer system hidden within your Mountaineer is constantly performing various routine checks on engine sensors, engine components and emissions components to verify everything is working correctly. Your vehicles computer has illuminated your gas cap light because there is a small evaporative or EVAP leak detected somewhere in the fuel system. Checking for a leak in the EVAP system is tedious and is generally left to dealerships and other repair shops who have special equipment for testing; however, there are several things that can be inspected without specialized equipment that may solve the problem.

Instructions

1

Open the fuel cap door and remove the fuel cap. Inspect the cap o-ring for any tears, rips or other damage and replace the cap if any of these conditions exist.

2

Install the cap to the vehicle and tighten it, it should click three times to ensure it is properly tightened and sealed. Drive the vehicle routinely for a day; if the light turns off, the cap wasn't properly tightened and the problem has been solved. If the light remained illuminated and the gas cap hasn't been replaced recently, purchase a new gas cap and properly install it. Monitor the gas cap light while driving the vehicle routinely, if the problem persists continue to the next step.

3

Lift the rear of the vehicle into the air and place jack stands under the rear frame rails. Lower the vehicle until it rests securely on the jack stands. Inspect the fuel fill hose for any damage or holes and inspect the fuel tank for any signs of a potential leak; even a small hole in the gas tank or fill tube will set the gas cap and/or check engine light. Inspect the evaporative vent lines running from the fuel tank to the EVAP cannister for any cracks or other damage and replace as necessary.

4

Check the electrical connector for the EVAP canister vent valve along with the wiring for any damage and repair as necessary. Remove the jack stands and lower the vehicle to the ground. After any repair to the evaporative system you need to drive the vehicle for a period of 30 minutes for the malfunction indicator to reset.

5

Anytime the PCM detects a problem in the evaporative system you will likely strain to find the exact source because even the smallest leak will be detected. If all else fails and you cannot locate the source of the leak, your only option is to connect a special smoke machine to the EVAP test port to find the exact source. Unfortunately the specialized equipment is expensive and you will likely have to take your mountaineer to a repair shop to be properly diagnosed.