How to Prime a Fuel Filter

by Grace Mclain

The fuel filter is the main component in the fuel system that keeps any and all fuel impurities from getting into the fuel injectors. Most fuel filters are made with fibers inside designed to trap and hold any impurities from the fuel. Impurities can include small particles of trash and debris. As the fuel circulates through the fuel filter, the fibers trap the impurities while allowing the cleansed fuel to travel to the fuel injectors and into the engine.

Priming a Gas Fuel Filter

Turn the ignition key to the accessory position for about five seconds and then back off again. Repeat this three times to prime the new fuel filter with gas.

Crank the engine on the fourth turn of the engine, and let it run for about 15 to 20 seconds.

Turn the engine off, and inspect the fuel filter for any signs of gas leaking from the fuel filter.

Priming a Diesel Fuel Filter

Place the diesel fuel filter in an upright position. Completely fill the diesel filter of fresh diesel.

Wait for the fibers inside the fuel filter to absorb the diesel. Finish filling the new fuel filter with diesel.

Screw the fuel filter tightly onto the fuel filter base. If the top of the fuel filter housing has a priming bulb, press in and out on the priming bulb with your hand until the bulb no longer will push in.

Turn the ignition to the accessory position for about 10 seconds. Crank the engine, and let it run for about 15 seconds.

Turn the engine off, and check the fuel filter for any leaks.


  • The purpose of turning the ignition on and off three times for the gas filter is to fill the new filter with gas and remove air from the fuel system.
  • The purpose of filling the diesel fuel filter with diesel and priming with the priming bulb and the ignition key is to also make sure the fuel filter is full of diesel and to remove all air from the fuel system.


  • If the fuel filters or fuel lines have any air inside them, it can cause vapor lock and prevent the engine from cranking.
  • Do not smoke or have open flames around gas.
  • Never dispose of fuel by dumping it onto the ground.

Items you will need

About the Author

Grace Mclain has been writing professionally since 1998. Her articles have appeared on eHow.com, Answerbag.com and LIVESTRONG.COM, and she specializes in automotive and business topics. McIain has a professional writing certificate from JB Hunt in Little Rock, Ark.

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