Replacing The Fuel Filler Neck In Your 03 Mustang

If you're looking to replace the fuel filler neck on your 2003 Mustang, you've come to the right place. This job can be done in a few hours with the right tools and some patience. Before starting, make sure your gas tank is as empty as possible, and disconnect the battery for safety. You'll need to raise the rear of the car, remove the right rear wheel, and place a jack under the fuel tank to support it. From there, you can remove the bolts holding the filler tube in place and carefully work it out of the tank. Be sure to clean the area around the filler tube gasket and remove the old gasket from the tank. With a new gasket and some grease or motor oil, you can then install the new filler neck, making sure to lubricate the new seal and filler tube. Finally, button everything back up and reconnect the battery. And there you have it! You've successfully replaced the fuel filler neck on your 2003 Mustang.

How to remove the filler neck

To remove the filler neck of a 1996-2004 Mustang, follow these steps:

• Ensure your fuel tank is not more than a quarter full.
• Disconnect the battery.
• Raise the car and support it with jack stands.
• Clean the filler tube and the area around the filler tube gasket.
• Remove the right rear wheel.
• Remove the 8mm bolt holding the filler tube in place.
• Remove the four 8mm bolts holding the upper end of the fuel tube to the fuel door cavity.
• Remove the two T15 screws and set the fuel door aside.
• Remove the two T15 screws with rubber stops.
• Remove the three 8mm screws inside the fuel door cavity.
• Inside the trunk, remove the passenger-side trunk liner.
• Separate the rubber vent tube from the plastic housing.
• Wiggle the plastic housing away from the filler tube.
• Work the fuel filler tube out of the fuel tank. You may need to jerk the tank and tube away from each other to separate them.
• Carefully remove the rubber gasket from the fuel tank.

Note: Some steps may vary depending on the year and model of your Mustang. Always refer to a qualified mechanic or an official repair guide for specific instructions for your vehicle.

How to install a new filler neck

This guide will take you through the process of installing a new filler neck on a 1996-2004 Mustang. Please note that this guide assumes you have a basic understanding of car mechanics and tools.

Step 1: Prepare the Car

• Ensure that your fuel tank is as empty as possible.
• Disconnect the battery.
• Raise the rear of the car using lifting ramps.
• Place a floor jack in the middle of the tank to support it.

Step 2: Remove the Old Filler Neck

• Unbolt the small loop attached to the filler neck from the tank.
• Slide off the plug from the plastic bracket that holds two wire harnesses together.
• Loosen and undo the tank straps, keeping the jack in place to support the tank.
• Drop the tank down and to the left, pulling the filler neck out at the same time.
• Remove the old filler neck carefully, as it will require some force but be careful not to break it.

Step 3: Prepare the New Filler Neck

Grease or lubricate the new filler neck grommet with Vaseline or motor oil. This will make it easier to install.

Step 4: Install the New Filler Neck

• Carefully insert the new filler neck into the tank, ensuring it is securely in place.
• Reattach the small loop to the filler neck and tank using a bolt.
• Reattach the plug to the plastic bracket holding the wire harnesses.
• Tighten the tank straps to secure the tank in place.
• Lower the car and reconnect the battery.

Step 5: Final Checks

• Check that the filler neck is secure and all connections are tightened.
• Refill your fuel tank and check for any leaks around the filler neck or tank.

Please note that this guide provides general instructions and your specific Mustang model may have unique requirements. Always refer to your vehicle's repair manual for detailed instructions specific to your car.

How to remove the old gasket

To remove the old gasket from your 2003 Mustang, you will first need to raise the car and support it with jack stands. Next, clean the filler tube and the area around the filler tube gasket.

Then, remove the right rear wheel. Remove the 8mm bolt holding the filler tube in place, followed by the four 8mm bolts holding the upper end of the fuel tube to the fuel door cavity. Remove the two T15 screws and set the fuel door aside. Also, remove the two T15 screws with rubber stops.

Now, you need to access the inside of the trunk. Remove the passenger-side trunk liner, and separate the rubber vent tube from the plastic housing. Wiggle the plastic housing away from the filler tube.

Work the filler tube out of the fuel tank, and carefully remove the rubber gasket from the fuel tank.

You can now proceed to install the new gasket.

How to install a new gasket

To install a new gasket on your 2003 Mustang, you will first need to purchase a new fuel filler neck gasket. You can find these online or at a Ford dealer. Once you have the new gasket, follow these steps:

• Disconnect the negative battery terminal.
• Loosen the lugs on the passenger rear tire.
• Raise the car and put it on jack stands, then remove the rear tire.
• Clean the filler tube and the area around the filler tube gasket.
• Remove the 8mm bolt holding the filler tube in place.
• Remove the 4 8mm bolts holding the upper end of the fuel tube to the fuel door cavity.
• Remove the 2 T15 screws and set the fuel door aside.
• Remove the 2 T15 screws with rubber stops.
• Remove the 3 8mm screws inside the fuel door cavity.
• Inside the trunk, remove the passenger-side trunk liner.
• Separate the rubber vent tube from the plastic housing.
• Wiggle the plastic housing away from the filler tube.
• Work the fuel filler tube out of the fuel tank and carefully remove the old rubber gasket from the fuel tank.
• Take the new gasket and rub a small amount of motor oil or petroleum jelly on it to ease installation.
• Place the new gasket on the fuel tank and rub a little oil on the inner part of the gasket to ease installation of the filler tube.
• Reinstall the filler tube, being careful to line up the gasket properly.
• Reinstall the fuel door and trunk liner.
• Reconnect the negative battery terminal.

This process should take around 30 minutes if you are working in a driveway. Be careful not to let any of the old gasket fall into the fuel tank, and make sure to support the fuel tank with jack stands during the process.

How to modify the filler neck to prevent overfilling

To modify the filler neck to prevent overfilling, you can try the following:

First, locate the filler neck by opening the fuel door. Check for any exterior damage and ensure all mounting screws are in place inside the fuel door area. Verify that the rubber hose and clamp are visible and undamaged. Some vehicles may have a cover protecting the fuel hose, which will need to be removed for inspection.

If you have an older vehicle, the fuel neck may have a short neck and a metal tube inside the fuel tank, connected by a long rubber hose with two clamps. In this case, you can try modifying the stock filler neck by adding a vent line to allow pressure to escape during filling. Here's how:

• Punch out the center of the filler neck to make room for the fuel flow.
• Add an external vent line to release pressure from the top of the filler neck when filling.
• Braze a fitting for a 3/4" hose into the filler neck. Ensure that the vent hose is positioned high enough so that vapour and air escape above the end of the pump nozzle.

Alternatively, you can purchase a filler neck kit, which will include a larger fill tube. This option may be more expensive, but it will ensure a proper fit and correct mounting. It is recommended to buy a filler neck from the dealership as an OEM product. Aftermarket products may not fit correctly.

When modifying or replacing the filler neck, always exercise extreme caution as fuel vapours are highly flammable. Do not smoke, and ensure the area is well-ventilated.

Frequently asked questions