How to Detect and Replace a Faulty Fuel Pump

January 27, 2012

Your car's fuel pump is responsible for pushing fuel into the engine of your car. When the fuel pump is defective or not operating at normal efficiency, your vehicle will not run smoothly or not at all. There are several tell tale signs of a faulty fuel pump, and your will be able to notice all of them without much effort.

Common Symptoms of a Bad Fuel Pump

  • The engine is hard to start or does not start. This is one of the most common symptoms of a faulty fuel pump. If you're having trouble starting your vehicle, or the vehicle does not start at all, you should first check the fuse for the field pump. If that doesn't do the trick, have the vehicle inspected by qualified mechanic
  • The engine stalls. If the flow of gasoline fluctuates, your engine may stall and this may be a sign that you need to replace the fuel pump
  • The engine surges. Just as too little gasoline being supplied to your engine will call it cause it to stall, too much gasoline will cause engine surges or surges in speed while driving. This also is a good indicator that you should check the fuel pump

How to Replace a Faulty Fuel Pump

Before replacing your faulty fuel pump you'll need to determine how the fuel pump is accessed in your vehicle. Some vehicles have a convenient fuel tank access point, usually located underneath the trunk liner or beneath the rear seat. Other vehicles are more complicated, and require removing the fuel tank to access the pump. It's best to acquire a service manual for your specific vehicle.

Tools and Materials

  • A floor jack
  • Jack stands
  • A socket wrench set
  • A replacement fuel pump
  • A siphon pump (optional)

Check Your Tank
Check your fuel gauge to determine the amount of fuel in your tank (if you have to remove it). Make sure the tank is no more than 1/8 full or you will have to siphon the gas out.

Relieve the Fuel System Pressure
The first thing you'll need to do on every vehicle is relieve the fuel system pressure. The fuel pressure can be relieved in most vehicles by removing the fuel pump relay, usually located in the engine bay fuse box, and removing the gas cap. Once these items are removed, crank your engine and let it run until it stalls and shuts off. This will starve your fuel lines of fuel and relieve pressure. Always disconnect the negative battery cable after you have relieved fuel system pressure.

Access the Fuel Tank
Next, you'll need to access the fuel tank. If your vehicle has a convenient access point, all you need to do is remove the screws and lift the cover off to access the fuel pump. If your vehicle does not, you'll need to begin removing the entire tank from beneath the vehicle. Lift your vehicle using a hydraulic floor jack and support it with jack stands. Make sure you lift and support the vehicle using only the manufacturer's recommended jacking points.

Remove Fuel Tank (If Necessary)
Removing the fuel tank is much easier with two people. Support the tank in its center with the floor jack and disconnect the tubes and hoses attached to the tank. Once they are disconnected, remove the fuel tank mounting braces. Once the braces are off, the fuel tank is ready to be lowered. Make sure you support the fuel tank while an assistant uses the jack to lower it to the ground. Be careful not to spill fuel—even if your tank is showing empty there is still a small amount of fuel in it.

Remove the Old Pump and Install the New Pump
Disconnect any electrical connections attached to the fuel tank and label the fuel lines for their location. You'll need to label or mark them to avoid crisscrossing them when installing the new pump. Pay close attention to the assembly of the old pump and then remove it. Attach the new fuel pump in the same manner and reattach the lines and connections.

Reinstall the Fuel Tank (If Necessary)
Lift the fuel tank back in position and keep it supported with the jack while you replace the mounting brackets or bolts. Reconnect the hoses and tubes. Once everything is put together, you can lower the vehicle and prepare the fuel pump for operation.

Repressurize the Fuel System
To repressurize a fuel system (this must be done before cranking), replace the negative battery cable, fuel pump relay and the gas cap. Turn your ignition key to the "On" position for a few seconds, but don't crank the engine. Repeat this procedure a few times and you're done.

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