How to Prime an Onan Generator


The Onan HDKAL is a 7.5 kilowatt commercial generator manufactured by Cummins Diesel. It is driven by a four-cycle, 3-cylinder Kubota D1105 engine and delivers 62.5 amps of 120V or 240V AC power. The electronic fuel injection system in the HDKAL is a Bosch K mini. The fuel system consists of a low-pressure side operated by the fuel lift pump and a high-pressure side operated by the fuel injection pump. Onan recommends a procedure to prime the low-pressure side for a number of troubleshooting scenarios such as the engine failing to start, or after the fuel tank has been run dry or the engine has been in storage. Onan recommends that only qualified diesel mechanics prime the high-pressure side.

Things You'll Need

  • 36-inch electrical jumper wire

Priming The Low-Pressure Side

  • Crank the engine for two 15-second periods, separated by a two-minute rest between crankings. If the engine does not start, proceed to prime the low-pressure side of the fuel system.

  • Remove the red positive (+) wire from its terminal on the fuel lift pump. The fuel lift pump is located on the left side of the engine block, toward the bottom, next to the fuel filter housing.

  • Connect a jumper wire directly from the positive(+) terminal of the generator's 12-volt cranking battery to the fuel lift pump positive terminal.

  • Allow the fuel lift pump to run for several minutes to purge air out of the fuel lines, fuel filter and injection pump.

  • Remove the jumper wire from the fuel lift pump terminal and replace the red power wire. Remove the other end of jumper from the 12-volt cranking battery pole.

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