Repriming Your Vehicle: Post Fuel Pump Change

Changing your vehicle's fuel pump is a big job, and there are several common problems that can occur after installation. These include electrical problems, fuel leaks, and issues with fuel pressure. If something goes wrong, it can cause your car to die or not start at all. To reprime your vehicle after changing the fuel pump, you'll need to add 5 to 10 gallons of fuel to the vehicle's tank, open the hood and operate the fuel lift pump by hand, and then start the engine using the normal procedure.

Relieve the fuel system pressure

Relieving the fuel system pressure is an important step when working on the fuel pump, fuel injectors, lines, and other related components. This is because the system operates under high pressure, which can be dangerous. Here is a step-by-step guide on how to relieve the fuel system pressure after changing the fuel pump:

• Disconnect the negative battery cable: Use a wrench to disconnect the negative battery cable. This will prevent sparks, which could ignite fuel and fuel vapors. Ensure you always do this when working on the fuel system of a car.
• Locate the fuel pressure regulator: The fuel pressure regulator is located on the fuel rail, which is mounted along the top area of the engine. Make sure that the regulator is vacuum-operated.
• Remove the vacuum hose: With your hand, carefully remove the vacuum hose from the top of the fuel pressure regulator. Be cautious, as there may still be fuel or fuel vapors present.
• Connect a hand-operated vacuum pump: Attach a hand-operated vacuum pump to the top of the pressure regulator. This will help draw out any remaining fuel in the lines.
• Apply vacuum pressure: Apply approximately 16 inches of Hg (mercury) vacuum pressure to the regulator. This will push the fuel in the lines back into the fuel tank, relieving the pressure in the system.
• Access the fuel pump assembly: Depending on your vehicle model, you may need to access the fuel pump assembly from the top of the fuel tank or from underneath the vehicle. Some models provide an access door to the fuel tank through the floor underneath the rear seat or in the trunk. If there is no access door, you will need to raise the rear of your vehicle using a floor jack and support it on jack stands to access the fuel pump assembly.
• Remove any necessary components to access the fuel pump: If your vehicle has an access door, you may need to remove the rear seat or the trim on the floor of the trunk. Use a Phillips screwdriver or carefully pull the butyl tape around the door to remove the mounting screws on the fuel tank access door.
• Ensure vehicle stability: If you are accessing the fuel pump from underneath, make sure the vehicle is securely supported on jack stands before crawling underneath.
• Unplug the fuel pump electrical connector: Locate the sending unit/fuel pump assembly and unplug the electrical connector.
• Start the engine and let it idle until it stalls: After unplugging the fuel pump connector, start the engine and let it run until it stalls.
• Turn off the ignition switch: Once the engine has stalled, turn off the ignition switch.
• Reinstall the fuel pump or perform other necessary repairs: At this point, you can reinstall a new fuel pump or perform any other necessary repairs or maintenance on the fuel system.
• Re-prime the fuel system: After completing your repairs, you will need to re-prime the fuel system. This may involve adding fuel to the vehicle's tank, bleeding air from the injection lines, and attempting to start the engine. Refer to your vehicle's repair manual or seek assistance from a qualified mechanic if you are unsure about the specific steps for your vehicle.

It is important to note that different vehicle manufacturers may have slightly different methods for relieving fuel system pressure. Always refer to your vehicle's repair manual or seek advice from a qualified mechanic if you are unsure about any steps. Working on a fuel system can be dangerous, so ensure you take the necessary precautions to avoid injury or damage to your vehicle.

Locate and remove the fuel tank

To locate and remove the fuel tank, you will need to follow a few steps. Firstly, it is important to note that the fuel tank's location can vary depending on the car model. In most cars, the fuel tank is located at the rear, underneath the vehicle. However, in some models, it may be positioned in the front or even inside the vehicle's cabin. Once you have identified the location, you can proceed to the next steps:

Step 1: Prepare the Vehicle

Park your car on a level surface and engage the parking brake. Ensure the engine is cool before beginning any work. Place wheel chocks or blocks behind the driving wheels for added safety.

Step 2: Locate the Fuel Tank

Crawl under the vehicle and look for the fuel tank. It is usually a large, rectangular or oval-shaped metal container. In some vehicles, it may be covered by a protective shield or panel, which you will need to remove to access the tank.

Step 3: Identify the Fuel Lines and Connections

Before removing the fuel tank, you must identify and disconnect all the connected fuel lines. These lines supply fuel to the engine and return the unused portion back to the tank. There may also be electrical connections or sensors attached to the tank, so take note of these and disconnect them carefully.

Step 4: Drain the Fuel

You will need to drain the fuel from the tank before removal. This can be done by using a fuel transfer pump or siphoning the fuel into an approved container. Ensure you work in a well-ventilated area and take the necessary precautions to avoid any sparks or open flames.

Step 5: Support the Tank

Place a jack or jack stands under the fuel tank to support its weight. This will prevent damage to the tank and any attached components during removal.

Step 6: Remove the Fuel Tank

Once all connections have been disconnected and the tank is supported, you can begin to remove it. Carefully lift the tank away from the vehicle, using the jack or jack stands to assist you. Slowly lower the tank to the ground, ensuring it does not come into contact with any hot engine components.

Remember to dispose of or recycle the old fuel tank responsibly, and always refer to your vehicle's repair manual for model-specific instructions and safety precautions.

Take note of fuel line connections and wiring

Taking note of the fuel line connections and wiring is a crucial step when reprimming your vehicle after changing the fuel pump. This is because the fuel pump is connected to various components, such as the fuel tank, engine, and fuel injectors, and improper connections can lead to fuel leaks and other issues.

Firstly, it is important to identify the fuel line connections. These are the points where the fuel lines connect to the fuel pump, engine, and fuel injectors. Make sure to take note of the routing of the fuel lines and any clamps or fasteners that secure them in place. When removing the old fuel pump, pay attention to how the fuel lines are connected and routed to ensure proper installation of the new fuel pump.

Next, take note of the wiring connected to the fuel pump. The fuel pump is an electrical component that receives power from the vehicle's electrical system. Identify the wires connected to the fuel pump and their routing to the vehicle's electrical system. Ensure that the wiring connections are secure and free from any damage or corrosion. A damaged or corroded wiring connector can cause resistance, limiting the power supplied to the fuel pump and affecting its performance.

Additionally, be cautious of the fuel pump relay and fuse. The relay controls the electricity supplied to the fuel pump, and a faulty relay may not provide enough voltage for the fuel pump to function correctly. The fuse protects the electrical circuit of the fuel pump, and a blown fuse will cause the fuel pump to malfunction. Therefore, it is essential to check and replace the fuse if necessary.

Furthermore, pay attention to the harness connector of the fuel pump. This connector provides the electrical connection between the fuel pump and the vehicle's electrical system. Ensure that the connector is clean and free from corrosion or damage. As previously mentioned, any issues with the wiring or connections can impact the performance of the fuel pump, leading to potential hard starting, rough idling, or even damage to the fuel pump.

Lastly, be mindful of the fuel pressure regulator and fuel filter. The fuel pressure regulator ensures that the fuel pump provides the correct fuel pressure to the engine. If the fuel pressure is too low, it can affect the engine's performance and fuel efficiency. The fuel filter, on the other hand, keeps dirt and debris out of the fuel system. A clogged fuel filter can restrict fuel flow and cause similar issues. Replacing the fuel filter when changing the fuel pump is recommended to ensure optimal performance.

Reassemble the fuel system

Reassembling the fuel system is the final step in changing your vehicle's fuel pump. Here is a detailed, step-by-step guide to ensure a safe and proper reassembly:

Firstly, it is crucial to take note of the fuel line connections and wiring before removing the old pump. Ensure you are familiar with the specific instructions for your vehicle's make and model, as the process can vary greatly. Once you have removed the old pump, you can begin the reassembly process.

Start by attaching the mounting brackets to the new fuel pump. Securely install the new pump in the same position as the old one, using the correct locking method for your vehicle. Some vehicles use a cam locking ring, while others have a metal cover tightened with nuts and fasteners.

Next, reconnect all the fuel line connections and wiring. Ensure that the fuel hoses are properly clamped and free of any cracks or damage. Lubricate the fuel hose connections with a small amount of petroleum jelly for a secure fit.

At this point, you should also replace the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket, if applicable. These components play an essential role in maintaining the fuel system's efficiency and longevity.

Before lowering the fuel tank back into the vehicle, clean the area around the fuel pump to prevent any dirt or debris from falling into the tank. Use a jack to support and lower the tank carefully.

Finally, fill the fuel tank and test for leaks. Start the engine and check for any signs of fuel leaks. Ensure that the new fuel pump is functioning properly and that there are no issues with fuel pressure or flow.

By following these steps carefully, you can safely and effectively reassemble your vehicle's fuel system after changing the fuel pump. Remember to refer to your vehicle's service manual or seek professional assistance if needed.

Test the new fuel pump

To test your new fuel pump, you should begin by checking if the problem is fuel-related. Check the fuel pump fuse in the fuse box. If the fuse is blown, it will be broken or burned. If the fuse looks good, check the rest of the fuses related to the fuel system. If no fuses are blown, listen for the fuel pump relay clicking on when turning the key.

If the fuse is blown, try replacing it and attempting to start the vehicle. If the fuse blows again, this indicates a direct short, which will need to be diagnosed by a mechanic.

Next, check the voltage at the pump itself. Consult your vehicle's service manual to find out where to check and the procedure for checking it. Test for source voltage to determine whether the charge leaving the fuse is reaching the pump. If no power is getting to the fuel pump, check the fuel pump relay circuit. You may have a bad relay.

You can also perform a drop test using a voltmeter. Check that the power wire shows the full voltage and the grounding wire is properly grounded. If this electrical test doesn't reveal any issues, it's likely that the fuel pump is the problem.

You can also perform a fuel pressure test. Remove the filter from the vehicle and drain any excess fuel. Use a short piece of rubber hose on the filter inlet and blow through, paying attention to the resistance. Inspect the screen for debris and replace the filter if necessary.

Get a fuel pressure gauge and hook it up to the fuel pump test point, which is usually located near the fuel injectors. Have an assistant rev the engine and check the pressure at idle speed and at the rated speed listed in your pump specifications. If you have a serious problem, the needle won't move or will drop below specifications, indicating that the fuel pump needs to be replaced.

Frequently asked questions