Electric Fuel Pump


Externally-Mounted Fuel Pump

When replacing an electric pump, be sure that the new or rebuilt replacement unit meets the minimum requirements of pressure and volume for that particular vehicle. This information can be found in the service manual. If the fuel pump is mounted in the fuel tank, the procedure for replacement is different than if the unit is external to the tank.

The in-tank pump can usually be taken out of the tank by removing the fuel sending unit retaining or lock ring. however, it may be necessary to remove the fuel tank to get at the retaining ring.

The following procedure pertains to an externally mounted fuel pump.

  • Before beginning to remove the fuel pump, disconnect the negative battery cable.
  • Then disconnect the electrical connectors on the electric fuel pump.
  • Label the wires to aid in connecting it to the new pump. Reversing polarity on most pumps destroys the unit.
  • Now disconnect the fuel and vapor lines at the pump. These lines should also be labeled to ensure that they are installed correctly on the new pump.
  • Loosen and remove the bolts holding the pump in place.
Fuel pump retaining bolts. Coutesy of American Honda Motor Company, Inc.
  • Remove the pump by pushing the pump up until the bottom is clear of the bracket.
  • Swing the pump out to the side and pull it down to free it from the rubber fuel line coupler.
  • The rubber sound insulator between the bottom of the pump and bracket and the rubber coupler on the fuel line are normally discarded because new ones are included with the replacement pump.
  • Some pumps have a rubber jacket around them to quiet the pump. If this is the case, slip off the jacket and put it on the new pump.
Avoid the temptation to test the new pump before reinstalling the fuel tank by energizing the pump with a couple of jumper wires. Running the pump dry can damage it, because the pump relies on fuel for lubrication and cooling.
  • Compare the replacement pump with the old one. If necessary, transfer any fuel line fittings from the old pump to the new one.
  • When inserting the new pump back into its bracket, be careful not to bend the bracket.
  • Make sure the rubber sound insulator under the bottom of the pump is in place.
  • Install a new filter sock (if so equipped) on the pump inlet and reconnect the pump wires. Be absolutely certain you have correct polarity.
  • If the fuel was removed from the vehicle, replace it.
  • Make sure all electrical connections are reconnected and that all fuel lines and hoses are properly fastened and tightened.
  • Then reconnect the ground terminal at the battery.
  • Start the engine and check all connections for fuel leaks.

Replacing an In-Tank Electric Fuel Pump

Never turn on the ignition switch or crank the engine with a fuel line disconnected. This action will result in gasoline discharge from the disconnected line, which may result in a fire, causing personal injury and/or property damage.

On many vehicles, the fuel tank must be removed to replace the fuel pump and/or fuel gauge sending unit. On other vehicles, the unit can be serviced through an opening in the vehicle's floor.

Some fuel pumps can be serviced through an access hole in the car's floor. Reprinted with permission.

Some vehicles have a separate fuel pump and gauge sending unit, while others have both contained in a single unit. Once the fuel tank is out of the vehicle, if necessary, remove the unit from the tank. Always follow the manufacturer's recommended procedure to remove the fuel pump and gauge sending unit from the fuel tank.

These units are often held in the tank by either a retaining ring or screws. The easiest way to remove a retaining ring is to use a special tool designed for this purpose.

Typical tool used to loosen and tighten the retaining ring for an in-tank fuel pump and/or fuel gauge sending unit. Courtesy of DaimlerChrysler Corporation.

This tool fits over the metal tabs on the retaining ring, and after about a quarter turn, the ring comes loose and the unit can be removed. If the special tool is not available, a brass drift punch and ball peen hammer will usually do the job.

Using a brass drift punch and ball peen hammer to loosen the retaining ring.

When removing the unit from the tank, be very careful not to damage the float arm, the float, or the fuel gauge sender. Check the unit carefully for any damaged components. Shake the float, and if fuel can be heard inside it, replace it. Make sure the float arm is not bent. It is usually wise to replace the filter and O-ring before replacing the unit. Check the fuel gauge and sender unit as described in the service manual. When reinstalling the pick-up pipe-sending unit, be very careful not to damage any of the components.

  • Once the unit is removed, check the filter on the fuel pump inlet. If the filter is contaminated or damaged, replace the filter. Inspect the fuel pump inlet for dirt and debris.
  • Replace the fuel pump if these foreign particles are found in the pump inlet.
  • If the pump inlet filter is contaminated, flush the tank with hot water for at least 5 minutes.
  • Dump all the water out of the tank through the pump opening in the tank.
  • Shake the tank to be sure all the water is removed. Allow the tank to sit and air dry before reinstalling it or adding fuel to it.
  • Remember, gasoline fumes are extremely ignitable so keep all open flames and sparks away from the tank while it is drying.
  • Check all fuel hoses and tubing on the fuel pump assembly.
  • Replace fuel hoses that are cracked, deteriorated, or kinked.
  • When fuel tubing on the pump assembly is damaged, replace the tubing or the pump.
  • Make sure the sound insulator sleeve is in place on the electric fuel pump, and check the position of the sound insulator on the bottom of the pump.
  • Clean the pump and sending unit mounting area in the fuel tank with a shop towel, and install a new gasket or O-ring on the pump and sending unit.
  • Install the fuel pump and gauge sending unit assembly in the fuel tank, and secure this assembly in the tank using the vehicle manufacturer's recommended procedure.