0343020 JOHNSON SPRING, Pressure relief

If the valve lash requires adjustment several times in a short period of time, excessive wear exists in a different part of the engine. Repair the problem in order to prevent more damage to the engine.Not enough valve lash can be the cause of rapid wear of the camshaft and valve lifters. Not enough valve lash can indicate that the seats for the valves are worn.Valves become worn due to the following causes:
Incorrect operation of fuel injection nozzles
Excessive dirt and oil are present on the filters for the inlet air.
Incorrect fuel settings on the fuel injection pump.
The load capacity of the engine is frequently exceeded.Too much valve lash can cause broken valve stems, springs, and spring retainers. Too much valve lash can be an indication of the following problems:
Worn camshaft and valve lifters
Worn rocker arms
Bent pushrods
Broken socket on the upper end of a pushrod
Loose adjustment screw for the valve lashIf the camshaft and valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.Valve Lash Check
An adjustment is NOT NECESSARY if the measurement of the valve lash is in the acceptable range. Check the valve lash while the engine is stopped. The clearance is specified in Table 1.
Table 1
Valve Lash    
Valves    Acceptable Clearance for Valve Lash    
Inlet    
0.20 mm (0.008 inch)    
Exhaust    
0.20 mm (0.008 inch)    If the measurement is not within the acceptable clearance, adjustment is necessary. Refer to the Systems Operation, Testing and Adjusting Module, "Valve Lash Adjustment" topic.Valve Lash Adjustment
The valve lash is measured between the top of the valve stem and the rocker arm lever. Refer to the Specifications Module, "Engine Design" topic for the correct valve lash.Note: No. 1 cylinder is at the front of the engine.Note: When these procedures are performed, the front housing must be installed.Perform the following procedures in order to adjust the valve lash:
Illustration 1 g00473333
Setting The Valve Lash (9) Set the valve lash with a screwdriver and with a wrench. (10) Measure the valve lash with a thickness gauge.
Illustration 2 g00396857
Sequence for setting the valve lash (typical example)Valve Lash for Three Cylinder Engines
Put the No. 1 piston in the top center position on the compression stroke. Refer to the Systems Operation, Testing and Adjusting Module, "Finding Top Center Position for No. 1 Piston" topic for the procedure to determine the top center position for the No. 1 piston on the compression stroke.
Use a thickness gauge (10) to measure the valve lash between the rocker arm and valve cap. If the valve lash must be increased, turn the adjusting screw on the rocker arm in a counterclockwise direction. If the valve lash must be decreased, turn the adjusting screw on the rocker arm in a clockwise direction.
Adjust the valve lash of the following valves:
Inlet valve of No. 1 cylinder (1)
Exhaust valve of No. 1 cylinder (2)
Exhaust valve of No. 2 cylinder (4)
Turn the crankshaft pulley for 240 degrees in a counterclockwise direction. Adjust the valve lash of the following valves:
Inlet valve of No. 2 cylinder (3)
Inlet valve of No. 3 cylinder (5)
Exhaust valve of No. 3 cylinder (6) Valve Lash for Four Cylinder Engines
Put the No. 1 piston in the top center position on the compression stroke. Refer to the Systems Operation, Testing and Adjusting Module, "Finding Top Center Position for No. 1 Piston" topic for the procedure to determine the top center position of the No. 1 piston on the compression stroke.
Use a thickness gauge (10) to measure the valve lash between the rocker arm and valve cap. If the valve lash must be increased, turn the adjusting screw on the rocker arm in a counterclockwise direction. If the valve lash must be decreased, turn the adjusting screw on the rocker arm in a clockwise direction.
Adjust the valve lash of the following valves:
Inlet valve of No. 1 cylinder (1)
Exhaust valve of No. 1 cylinder (2)
Inlet valve of No. 2 cylinder (3)
Exhaust valve of No. 3 cylinder (6)
Rotate the crankshaft pulley for 360 degrees in a clockwise direction. Adjust the valve lash of the following valves:
Exhaust valve of No. 2 cylinder (4)
Inlet valve of No. 3 cylinder (5)
Inlet valve of No. 4 cylinder (7)
Exhaust valve of No. 4 cylinder (8)