HOW IT WORKS
1979 M2ME ALL (EXCEPT 3.3L V6)
In addition to vacuum enrichment, this carburetor has a mechanical enrighment system which starts to operate from a specified throttle valve opening to wide open throttle. This provides accurate control of fuel mixtures at high engine speeds and load and yet allows the use of vacuum enrichment for improved fuel control during medium engine loads.
The mechanical enrichment is controlled by a stem pressed into the base of the power piston which extends into the throttle body. The stem is operated by a lever which is hinged to the throttle body casting and a cam on the center of the throttle shaft. When the throttle valves are opened to a pre-determined point, the cam on the throttle shaft forces the lever upward until it contacts the stem on the power piston and pushes the complete piston assembly upward against engine vacuum. This, in turn, lifts the metering rods, placing the smaller diameter of the metering rods in the man metering jets for positive mixture enrichment at great throttle valve openings.
The power piston has a "trapped" spring which limites the travel of the piston during vacuum operation. The spring is retained between the piston and a fluted washer on the power piston stem. The washer is retained with a "c" clip located in a groove on the power piston stem.
During high engine vacuum, the power piston spring is compressed and the fluted washer and piston are seated at the bottom of the power piston cavity. As engine load increases, vacuum drops and the power piston moves upward against spring tension until the "c" clip seats against the fluted washer. No more enrichment will take place until the pin in the power piston is contacted by the mechanical enrichment lever. As the throttle valves are opened further, the complete power piston assembly is forced upward placing the smaller diameter of the metering rods in the jets for maximum enrichment at higher engine speeds and loads.
When engine load and speed is decreased, the power piston will return to the down position, seating the fluted washer and piston in the bottom of the power piston cavity as high engine vacuum compresses the power piston spring. This returns the metering system to leaner mixtures for light engine loads.
1979 M2ME POWER SYSTEM 3.3L 200" V6
The combination vacuum-mechanical power enrighment system is no long used on the M2ME carburetor for the 3.3L engine. The fully vacuum operated power enrichment system is used for improved performance in the intermediate range of engine operation.
