Replacing the air filter element

The air filter element is located in the air filter housing, or on the carburetor, or on the CFI unit, or on the left front side of the engine compartment. Unscrew the mounting screws, or disconnect the brackets, and remove the air filter cover (see fig. 1 22-1.27).













Remove the air filter cover and remove the filter element.


When performing normal maintenance, the filter element must be replaced regardless of condition.

Warning. Do not run the engine even for a short time without a filter element, as dirt that has entered the cylinders will lead to intensive engine wear.

Checking the supply air temperature control system (fuel system with carburetor)

For efficient operation of the engine, it is necessary that the temperature of the air entering the system is within certain limits.

Air enters the air filter in two ways, the first directly from the engine compartment, and the other from the shroud on the exhaust manifold. On HCS engines, the wax controlled thermostat valve operates a flap inside the air filter inlet. When the ambient air temperature is below a predetermined level, the flap allows air heated from the exhaust manifold shroud to pass through; when the temperature rises, the flap opens and allows cooler air from the engine compartment to pass through.

A similar system is used on CVH engines. except that the vacuum actuator changes any opening or closing action of the temperature sensor on the flapper valve, according to the intake manifold vacuum level.

HCS engines

The check is made on a cold engine. Remove the air filter. Examine the position of the control valve within the duct. When the air temperature is below 28°C, the valve must be opened to allow hot air to enter the filter (see fig. 1.28).



Connect the inlet with a pipe. Start the engine and warm it up to normal operating temperature, then stop the engine, remove the pipe from the inlet and check that the valve closes the warm air supply and opens the cold air supply directly from the engine compartment.


If the flap does not work, check that it is not jammed. In case of any defect, the valve must be replaced.

CVH engines.
The check is made on a cold engine. Disconnect the inlet fitting and check that the flap is open to let in cold air.

Start the engine and warm it up to normal operating temperature, the valve should open to allow warm air to flow from the exhaust manifold area (see fig. 1.29).



If the flap does not work, check that it is not jammed, and also check the condition of the vacuum pipe and the operation of the flap valve.