1. The main components of the injection pump are as follows.

      Components Function
      HAC (High-Altitude Compensator) The low atmospheric pressure and thin air density at high altitudes would cause the air-fuel mixture to become over-rich and the density of the exhaust smoke to rise. To prevent this from occurring, the HAC automatically reduces fuel injection volume in accordance with the vehicle's present altitude.
      ACSD (Automatic Cold Start Device) To improve startability, this device both advances the injection timing and maintains a fast idle condition when the coolant temperature is low.
      TCV (Timing Control Valve) TCV which control the injection timing, install between high pressure room and low pressure room.

    1. HAC (High-Altitude Compensator)

      1. The HAC is composed of a vacuum bellows, push rod, connecting pin, control arm, etc.

        Text in Illustration
        *1 Atmosphere Chamber *2 Vacuum Bellows
        *3 Connecting Pin *4 Push Rod
        *5 Control Arm *6 Tension Lever
        *7 Guide Lever - -
    2. Injection Nozzle

      1. As in the 3L engine, a compact and lightweight injection nozzle is used.


    1. HAC (High-Altitude Compensator)

      1. Under high atmospheric pressure, the bellows are contracted and the push rod is pulled upward by the spring. Conversely, under low atmospheric pressures, there is less pressure on the bellows, so they expand, causing the pushrod to move downward.

        Text in Illustration
        *1 Bellows *2 Control Arm
        *3 Tension Lever *4 Spill Ring
        *a Expand *b Fuel Decrease
    2. ACSD (Automatic Cold Start Device)

      1. When the coolant temperature is low, the thermowax is contracted, allowing lever A to be pushed to the right by the force of the return spring. The cam rotates the roller ring and moves the timer piston in the advance direction in order to achieve the amount of advance that suits the coolant temperature. Furthermore, lever B moves the adjusting lever in order to automatically adjust the idle speed.

        Text in Illustration (Cold Engine:)
        *1 Adjusting Lever *2 Lever A
        *3 Lever B *4 Coolant
        *5 Thermo Wax *6 Cam
        *7 Automatic Timer - -
        *a Advance *b A-A Cross Section
      2. When the coolant temperature increases, the thermowax expands, overcomes the tension of the return spring, and moves lever A to the left in order to reduce the amount of advance. Furthermore, lever B decreases the idle speed in an effort to reduce the fuel consumption rate.

        Text in Illustration (Warm Engine:)
        *a Retard *b A-A Cross Section
    3. TCV (Timing Control Valve)

      1. At high altitude, low coolant temperature or high load (sensed by engine speed and throttle position sensor), the emission control ECU sends signals to TCV. Then, the path is shut off and the injection timing is advanced.