Switching Engine Fuel: A Step-By-Step Guide For Beginners

Changing the fuel in an engine is a complex process that requires careful consideration and planning. It involves a range of tasks, from relieving pressure in the fuel system to disconnecting batteries and fuel lines. The process may vary depending on the type of engine and vehicle, but the basic steps remain consistent. It is important to refer to the vehicle's service manual for specific instructions and to take all necessary safety precautions when performing any fuel-related work.

How to relieve pressure in the fuel system

To relieve pressure in the fuel system, you can try the following methods:

Relieving Pressure with the Fuel Pressure Regulator

• Disconnect the negative battery cable using a wrench to prevent sparks that could ignite fuel and fuel vapors.
• Locate the fuel pressure regulator on the fuel rail, which is mounted along the top area of the engine. Ensure that the regulator is vacuum operated.
• Remove the vacuum hose from the top of the fuel pressure regulator by hand.
• Connect a hand-operated vacuum pump to the top of the pressure regulator.
• Apply about 16 inches Hg of vacuum to the regulator to push the fuel in the lines back into the fuel tank.

Relieving Pressure with the Fuel Pump Connector

• Access the sending unit/fuel pump assembly on top of the fuel tank. Some vehicle models provide an access door to the fuel tank through the floor underneath the rear seat or under the trim in the trunk. For other models, you may need to raise the rear of your vehicle using a floor jack and support it on two jack stands to access the sending unit/pump assembly.
• If your model has an access door above the tank, remove the rear seat by pulling the retaining strap on the back of the seat and lifting it, or remove the trim on the floor of the trunk. Remove the mounting screws on the fuel tank access door using a Phillips screwdriver or by pulling the butyl tape around the door.
• If the fuel pump is accessed from underneath, ensure that the vehicle is secured on the jack stands before locating the fuel pump assembly.
• Unplug the fuel pump electrical connector on the sending unit/pump assembly.
• Start the engine and let it idle until it stalls. Then, turn off the ignition switch.

Relieving Pressure with the Fuel Pump Fuse and Relay

• Locate the fuel pump fuse under the dashboard or in the engine compartment, usually on the driver's side of the vehicle. It is typically marked for easy identification and can also be found in your owner's manual.
• Remove the fuse with your hand, a pair of pliers, or remove the fuel pump relay by hand.
• Start the engine and let it idle until it stalls.
• Disconnect the negative battery cable using a wrench.

Relieving Pressure with the Ford Inertia Switch

• Search for the inertia switch around the trunk, rear compartment, or under the dashboard. Many Ford models use this shut-off switch to cut off fuel to the system in case of an accident. You can consult your owner's manual for reference.
• Unplug the inertia switch's electrical connector.
• Start the engine and let it run until it stalls.
• Disconnect the negative battery cable.

Relieving Pressure with the Test-Port Valve

• Disconnect the negative battery cable.
• Search for the Schrader valve on the fuel rail around the top of the engine if your vehicle is equipped with a fuel injection system. Some models use this valve for test purposes, and it resembles the air valve on a bicycle tire.
• Unscrew the valve cap if there is one.
• Wrap one or more shop rags around the port valve to catch any fuel that may squirt out as you depressurize the system.
• Push the valve in using a small screwdriver until fuel stops pouring through.
• Replace the test-port valve cap.

Additionally, always loosen or remove the fuel filler cap on your vehicle when working on the fuel tank to relieve pressure build-up. Always disconnect the negative battery cable when working on the fuel system of a car.

How to remove the old fuel filter

Before you begin, relieve the pressure in your vehicle's fuel system and disconnect the battery. You should also jack up your vehicle if the filter is underneath it rather than in the engine bay.

Now, locate the fuel filter. There are two common locations that fuel filters are mounted in vehicles. The most common location for modern vehicles is along the fuel line on the bottom of the car, just past the fuel pump. In some vehicles, the fuel filter is located in the engine bay on the line that leads to the fuel rail. You may need to access the fuel filter from inside the cabin of some vehicles, so refer to your vehicle's service manual to help you determine which place to look.

Place a bowl or bucket beneath the fuel filter to catch any fuel that drips or pours out when you disconnect the fuel lines. Be careful of using plastic containers to hold gas, as it may eat through some kinds of plastic and cause a leak.

Most fuel filters are held in place by two plastic clips. Locate the clips on either side of the cylindrical fuel filter, then use a flat-head screwdriver to pop them out. These clips may break as you remove them, so purchasing replacement clips along with your new fuel filter is advised.

With the clips removed, slide the fuel lines away from the filter to pop them off the nozzles at either end. Make sure to tip the fuel lines toward the bowl or bucket to catch any spilled gasoline. You should wear eye protection and gloves during this portion of the project to protect you from fuel splatter.

The fuel filter is likely held in place by a metal bracket that wraps around its outer housing. With the fuel lines disconnected, you can slide the fuel filter out of the bracket by pushing it toward the front of the car. The fuel filter will have a slight bell shape, allowing it to slide out in only one direction. If your filter sits in the bracket differently, you may need to slide it toward the back of the car to remove it. Some fuel filters under the hood may be held in the bracket with a bolt that will need to be removed to slide the filter out.

How to install a new fuel filter

Step 1: Compare the new filter to the old one

Before installing the new fuel filter, compare it with the old one to ensure they are the same. Check that they have the same outside diameter, nozzle size, and bracket fit. If they don't match, you will need to return the new one for the correct replacement. Do not attempt to use a fuel filter designed for a different vehicle.

Step 2: Slide the new fuel filter into the bracket

The new fuel filter should easily slide into its bracket. If you have to force it, it is likely that it is not the correct size. Be careful not to damage the housing of the fuel filter, as this may cause a leak.

Step 3: Fasten the fuel filter to the fuel line

Slide the fuel lines onto the front and back of the new filter in the same way they were attached to the old one. With the fuel line in place, secure it by sliding the plastic clips through the holes on the fuel line nozzle. Ensure the fuel lines are snug on the nozzles before sliding the clips into place.

Step 4: Lower the vehicle

If you have jacked up your vehicle, you will now need to lower it. Jack up the car to relieve the weight on the jack stands, then slide them out from beneath the vehicle. Once the jack stands are clear, lower the vehicle to the ground. Be sure the jack stands are completely out of the way, otherwise, they may damage the vehicle.

Step 5: Reconnect the battery

Once the vehicle is safely on the ground, reconnect the battery to complete the installation.

How to disconnect the battery

Disconnecting a car battery is a relatively simple process that can be done without taking your car to a mechanic or auto shop. Here is a step-by-step guide on how to disconnect your car battery:

Step 1: Turn Off the Engine

Begin by turning off your engine and removing the keys from the ignition. It is unsafe to disconnect the battery with the engine running as it could cause bodily injury and vehicle damage.

Step 2: Locate the Battery and Terminals

The battery is typically located in the engine compartment, but some cars have batteries in the trunk or under the rear seat. Consult your vehicle's manual to determine the battery's exact location. The negative terminal should display a negative symbol (-) and usually has a black cable, while the positive terminal should have a positive symbol (+) and usually has a red cable.

Step 3: Disconnect the Negative Terminal

It is important to disconnect the negative terminal first to prevent any electrical shorts. Use a wrench to loosen the nut or bolt securing the terminal. After it is loose, carefully lift the cable off the battery post and set it aside.

Step 4: Disconnect the Positive Terminal

Repeat the same process for the positive terminal, but make sure that the positive and negative terminals do not touch each other or any metal surface. Isolate the positive cable end by wrapping it in a non-conductive material such as a towel.

Step 5: Loosen and Remove the Battery Hold-Down

The battery hold-down holds the battery in place while driving the vehicle. Locate the fasteners and loosen or remove them as necessary with your wrench, then remove the battery hold-down.

Step 6: Remove the Battery

Carefully remove the battery, ensuring it remains level as you pull it out from the vehicle to prevent battery acid from spilling. Be mindful of its weight. Car batteries can weigh 40 pounds or more, so lift with your legs to avoid back injury. After removing the battery, set it on a dry, flat surface.

Safety Precautions

When disconnecting a car battery, it is important to prioritise safety. If done incorrectly, it can cause physical injury, permanently ruin your battery, destroy your vehicle's onboard computers, and/or blow fuses. Wear protective gloves, aprons, and goggles to shield yourself from potential hazards. Additionally, remove any metal jewellery to prevent accidental short circuits.

How to locate the fuel filter

Locating the fuel filter is the first step in changing your engine fuel. It is positioned between the car's fuel pump and the fuel injectors. The fuel filter is designed to filter out rust, dirt, and other impurities from the fuel, protecting the fuel pump and injectors from contamination.

There are two common locations for fuel filters in vehicles. The most common location for modern vehicles is along the fuel line on the bottom of the car, just past the fuel pump. In some vehicles, the fuel filter is located in the engine bay on the line that leads to the fuel rail. Some vehicles may have the fuel filter in a different location, so it is important to refer to your vehicle's service manual to determine the exact placement.

If your vehicle has fuel injection, the fuel filter will be located in the high-pressure fuel line, either under the vehicle near the fuel tank or under the hood in the fuel line near the engine. Some vehicles also have a fuel filter in the fuel pump itself, as well as a filter screen inside the fuel tank. If these get blocked, it is recommended to have a professional address them.

Before attempting to locate the fuel filter, it is important to relieve the pressure in the fuel system. This can be done by locating and removing the fuel pump fuse or relay in the fuse box, then starting the engine and letting it run until it stalls. This will depressurize the fuel system and make it safer to work on.

Once the pressure is relieved, you can proceed to locate the fuel filter. Refer to your vehicle's service manual for specific instructions on accessing and replacing the fuel filter. This process may vary depending on the vehicle's make, model, and year.

Frequently asked questions