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  • Repriming a Bosch VP44 Cummins Injection System

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    Mopar1973Man

    Reprime Bosch VP44 Injection Pump The Fuel System Cummins

    This is an article on how to reprime the Bosch VP44 Injection fuel system on a 24V Dodge Ram Turbo Cummins.

    A certain amount of air becomes trapped in the fuel system when fuel system components on the supply and/or high-pressure side are serviced or replaced. Primary air bleeding is accomplished using the electric fuel transfer (lift) pump. If the vehicle has been allowed to run completely out of fuel, the fuel injectors must also be bled as the fuel injection pump is not self-bleeding (priming). Servicing or replacing components on the fuel return side will not require air bleeding.

    DANGER! DO NOT BLEED AIR FROM THE FUEL SYSTEM OF A HOT ENGINE.

    1. Loosen, but do not remove, banjo bolt (test port fitting) holding low-pressure fuel supply line to the side of Bosch VP44 injection pump. Place a shop towel around banjo fitting to catch the excess fuel. The fuel transfer (lift) pump is self-priming: When the key is first turned on (without cranking engine), the pump operates for approximately 2 seconds and then shuts off. The pump will also operate for up to 25 seconds after the starter is quickly engaged, and then disengaged without allowing the engine to start. The pump shuts off immediately if the key is on and the engine stops running.
    2. Turn the key to CRANK position and quickly release the key to ON position before engine starts. This will operate fuel transfer pump for approximately 25 seconds.
    3. If fuel is not present at fuel supply line after 25 seconds, turn key OFF. Repeat previous step until fuel is exiting at fuel supply line.
    4. Tighten banjo bolt at fuel supply line to 24 N·m (18 ft. lbs.) torque. Primary air bleeding is now completed.
    5. Attempt to start the engine. If the engine will not start, proceed to following steps. If the engine does start, it may run erratically and be very noisy for a few minutes. This is a normal condition.

    Continue to next step if:

    • The vehicle fuel tank has been allowed to run empty
    • The Bosch VP44 fuel injection pump has been replaced
    • High-pressure fuel lines have been replaced
    • Vehicle has not been operated after an extended period

    WARNING! Do not engage the starter motor for more than 30 seconds at a time. Allow two minutes between cranking intervals.

    1. Perform previous air bleeding procedure steps using fuel transfer pump. Be sure fuel is present at fuel supply line before proceeding.
    2. Crank the engine for 30 seconds at a time to allow air trapped in the injection pump to vent out the drain manifold.

    DANGER! THE FUEL INJECTION PUMP SUPPLIES EXTREMELY HIGH FUEL PRESSURE TO EACH INDIVIDUAL INJECTOR THROUGH THE HIGH-PRESSURE LINES. FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE THE SKIN AND CAUSE PERSONAL INJURY. WEAR SAFETY GOGGLES AND ADEQUATE PROTECTIVE CLOTHING AND AVOID CONTACT WITH FUEL SPRAY WHEN BLEEDING HIGH-PRESSURE FUEL LINES. WARNING: ENGINE MAY START WHILE CRANKING STARTER MOTOR.

    DANGER! ENGINE MAY START WHILE CRANKING STARTER MOTOR.

    The engine may start, may run erratically and be very noisy for a few minutes. This is a normal condition.

    1. Thoroughly clean area around injector fittings where they join injector connector tubes.
    2. Bleed air by loosening high-pressure fuel line fittings at cylinders number 3, 4 and 5.
    3. Continue bleeding injectors until engine runs smoothly. It may take a few minutes for the engine to run smooth.
    4. Tighten fuel line(s) at injector(s) to 38 N·m (28 ft. lbs.) torque.


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