This system applies to diesel engines only.
The high altitude emission control system is designed to control the formation of HC and CO emissions and to improve the driveability of the car in high altitude areas. In order to ensure decreased exhaust emissions, the injection timing and EGR tube have to be changed/replaced.
There is an altitude compensator located on top of the injection pump. The altitude shaft is in contact with a pin which is connected to the control lever which is in contact with the governor lever. The higher the altitude, the lower the atmospheric pressure. Due to this fact, the pressure inside the aneroid is higher than that of the atmosphere at high altitudes, which causes the aneroid to expand like a balloon. When this happens, the aneroid shaft is pushed down, changing the contact surface with the pin, thus decreasing the fuel. Hence, the system controls the amount of fuel supplied in direct proportion to the altitude.