MAINTENANCE ITEMS Air Pump Drive Belt	It is important that the air pump drive belt be correctly tensioned to ensure efficient operation of the air injection system. When the belt is correctly adjusted, a total deflection of 1/2 in (13 mm) should be possible under normal finger pressure at the midway point of the belt run between the two pulleys. If adjustment is necessary, slacken the pump securing bolts and the adjusting link bolt and move the pump to the required position to achieve the correct tension . Avoid over-tightening the belt. Recheck the tension after tightening the adjusting link and pump mounting bolts. The condition of the pump drive belt should also be checked periodically and the belt replaced if nicked, cut, excessively worn or otherwise damaged. To replace the belt, proceed as for adjusting but press the pump fully in towards the engine and detach the belt from the air pump and water pump pulleys. Feed the belt between the tips of the fan blades and the radiator cowling at the top as the blades are rotated, then pull the belt out from between the fan and radiator. It may be necessary to detach the radiator top mounting bracket and top hose and pull the radiator away from the engine to obtain sufficient clearance for the old belt to be removed and the new one fitted. Adjust the tension of the new belt as described above. It should be noted that the tension of a new belt should be checked after approximately 100 miles (160 km) use.
Gulp Valve	To check the operation of the gulp valve, first disconnect the air supply hose at the air pump. Connect a 'T' adaptor and vacuum gauge to the gulp valve hose, as shown in . Start the engine and run it at idle speed; the engine must remain at idle during this test. Seal the open end of the 'T' adaptor with the finger and check that the vacuum gauge reads zero for approximately 15 seconds. If a vacuum reading is obtained, the gulp valve must be renewed. Repeat the test, but open the throttle rapidly; the gauge should register a vacuum reading. Remove the finger from the 'T' piece to release the vacuum. Repeat this test several times. If a vacuum is not registered, renew the gulp valve. When the test is completed remove the gauge and 'T' adaptor and reconnect the air supply hose. Tighten the hose clips securely.
Diverter Valve	The air diverter valve which controls the air supply to the injection manifold is actuated by the operation of the carburettor choke mechanism and may be either cable operated, or vacuum operated on early models. In either case the general condition of the diverter valve should be checked before attempting to check its operation. Also ensure that the air silencer is in place. To check the operation of the cable-operated type valve, first pull out the choke control knob sufficiently to obtain a clearance of 0.010 . 0.015 in (0.25 - 0.38 mm) between the jet housing and the adjusting nut at the carburettor. Check the clearance between the operating lever and the valve stem at the diverter valve. This should be 0.0015 - 0.003 in (0.04 - 0.08 mm). If necessary, slacken the trunnion at the operating cable and adjust the position of the operating lever to obtain the correct setting. Retighten the trunnion. Disconnect the air supply hose from the exhaust check valve. Start the engine and run it at idle speed. Air pressure should be felt at the air supply hose end. Pull out the choke control knob and check that the air supply is now completely cut off. If air pressure is still felt at the hose end, the diverter valve is defective and must be renewed. The checking operation is similar for the vacuum operated type diverter valve, but obviously the cable adjustment procedure given above will not apply in this case.
Exhaust Check Valve	The exhaust check valve can be easily tested once removed from its location in the pump supply line. When disconnecting the valve from the air manifold, hold the manifold union to prevent it twisting while unscrewing the valve. Using the mouth, blow into the valve from each end in turn. Air should only pass through the valve from the air supply end (hose connection end). If air passes through from the threaded (air manifold) end, the valve is defective and must be renewed.
Air Temperature Control Valve	The air temperature control valve is incorporated in the air intake to the air cleaner and its operation can be checked by depressing the valve flap, then releasing it The valve should return easily to its original position. The valve seat should also be inspected for any signs of damage or deterioration. When the engine is cold, the valve should be in the closed position, so that only hot air from around the exhaust manifold is drawn into the cleaner intake.
Fuel Line Filter	An inline fuel filter is incorporated in the fuel supply line at the carburettor, and should be renewed as an assembly at the recommended intervals. Ensure that the new filter is fitted with the flow arrow pointing towards the carburettor. On some types of filter the filter inlet con connection may be marked 'IN' instead, and the inlet hose should be connected to this side.
Absorption Canister	The absorption canister for the Fuel Evaporative Loss Control system must be renewed at t e recommended intervals to ensure proper and efficient operation of the system. The canister is easily replaced in the following way: After disconnecting the hoses, remove the retaining screw and open the bracket sufficiently to withdraw the canister. Ensure that the hoses are properly and securely reconnected to the canister. At the same time, disconnect the purge hose from the rocker cover elbow and examine the restrictor orifice for any signs of dirt or deposits. Clean, if necessary, using a length of soft wire. Reconnect the purge hose.
Carburettor Throttle Damper	Where a throttle damper is fitted at the carburettor, its setting should be checked and adjusted if necessary. The air cleaner and air temperature control valve assembly must first be removed to allow access. The engine idle speed must also be correctly set before carrying out this check. Insert a 0.080 in (2.03 mm) feeler gauge between the lever pad and the damper plunger and depress the lever The idle adjusting screw should contact and the damper plunger should be fully depressed. If not, the damper lever should be adjusted as follows. Slacken the lever clamp. Insert the feeler gauge between the lever pad and the damper plunger. Depress the lever and hold the plunger at the bottom of its stroke. Ensure the throttle is closed and that a clearance exists between the lever clamp and the carburettor body. Retighten the clamp nut and check the action of the throttle linkage. Finally, refit the air cleaner and temperature control valve.
Carburettor Tuning	The use of an Exhaust Gas Analyser (Co meter) is essential to check the carburettor mixture setting and, as it is unlikely that the normal ownerdriver will possess such expensive equipment, it is therefore advised that the checking and adjustment of the carburettor settings be left to an Authorised Dealer or Specialist. On models fitted with Emission Control equipment, additional maintenance items must be carried out at specified intervals to ensure that the systems operate at their correct level of efficiency (see Technical Data). The efficient operation of the systems is also dependent on the general state of tune of the engine and great care must be taken to ensure that the engine and its associated components (valve clearances, ignition and spark plug settings, carburettor setting etc.) are in good condition and/or correctly adjusted in accordance with the specifications given in 'Technical Data'.