How to Start a Fuel Pump Without Going Through the Ignition

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When the electric fuel pump in your gas tank fails to operate, it does not mean that the pump motor or pump circuit has failed. The ignition switch wire loom might be defective, causing a short to one or several wires. The relay or in-line fuse to the pump could be shorted or melted, cutting off the voltage to the pump motor. To bypass the ignition switch and check the fuse box condition, a repair person will need several feet of jumper wire and some small spade connectors. With the aid of a few tools and simple steps, he can restore power to the fuel pump with a simple bypass method.

Things You'll Need

  • Owner's repair manual
  • Socket set
  • Ratchet wrench
  • Felt pen
  • Jumper wire
  • Spade connectors
  • Wire strippers
  • Screwdrivers
  • Set the vehicle shift selector in park or neutral, for either an automatic or manual transmission. Raise the hood. Disconnect the negative battery cable with a socket and wrench. Refer to your owner's manual for the location of your main fuse box. Some fuse boxes sit inside the engine compartment next to the fire wall, while others can be located underneath the driver's side kick panel or inside the glove box. Unsnap the clasps on the fuse box lid and pull it off.

  • Look at the schematic on the inside of the fuse box for the location of the fuel pump relay. The relay looks like a small plastic box, and it plugs into the fuse box chassis. Pull out the relay. Look at the pin connector numbers on the underside of the relay. They will have numbers such as 31, 30 87 and 31b. The numbers represent the different components the wires lead to. Open up your repair manual and find the schematic wiring diagram for the fuel pump relay.

  • Locate the pin location for the 12-volt chassis ground and the 12-volt fuel pump pin. Match the relay pins on the fuse box slots. Use a felt pen to write "FP" next to the fuel pump slot and write "G" next to the chassis ground slot. Use wire strippers to cut a length of wire that will reach from the positive post on your battery to the relay. Cut another length of wire that will reach from the relay to any screw that fastens to bare metal on the underside of the dashboard frame.

  • Strips the ends of both wires with wire strippers. Place two spade connectors on each wire end and crimp them closed with the wire strippers. Plug the spade of the short wire into the 12-volt ground slot in the fuse box. Strip the other end of the ground wire and twist the strand. Use a screwdriver to loosen a screw from the dashboard and slip the ground wire around its threads. Tighten the screw. Plug the 12-volt spade connector into the 12-volt fuel pump slot.

  • Take the long fuel pump wire to the your battery. Strip the end of the wire, leaving about 2 inches of bare wire. Use a socket to remove the battery clamp nut on the positive side of the battery. Wrap the wire around the battery clamp bolt and tighten the clamp with a socket. Reconnect the negative battery cable with a socket. Slip under the rear part of the vehicle and hold a long screwdriver between your ear and the fuel tank. The fuel pump motor will begin running.

References

  • Photo Credit woman trying to fix car while husband relaxes image by David Smith from Fotolia.com
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