BCDD Operation

1. Place gear shift lever in neutral position and connect rubber hose between vacuum gauge and intake manifold.
2. With engine at operating temperature, adjust idle to specification.
3. With engine under no load, increase engine speed to 1500-2000 RPM, then quickly close throttle valve.
4. Manifold vacuum pressure should abruptly rise to 23.62 inches Hg or above, then gradually decrease to a certain level and stay there for a while. This is the operating pressure. In most cases it will drop to idle pressure.
5. Check that bypass air control valve pressure is within specified range which should be (at sea level) 22.83-24.41 inches Hg.
6. If it is lower than specified level, turn adjusting screw counterclockwise until correct adjustment is made. If it is higher turn adjusting screw clockwise.
7. Race the engine and check for adjustment.
8. If engine speed cannot be reduced to idle when checking BCDD operating pressure, turn adjusting screw counterclockwise until BCDD operating pressure is on high vacuum side, .98 inch Hg from specified pressure, then turn adjusting screw 1/4 turn clockwise so that BCDD operating pressure drops .98 inch Hg.
9. If BCDD operating pressure is still not accurately determined, turn adjusting screw counterclockwise so that BCDD operating pressure is on high vacuum side, 1.97 inches Hg from specified pressure, then turn adjusting screw 1/2 turn clockwise.
10. Boost control unit operating pressure should be correctly set within specified range even if engine speed cannot be decreased to idle.