C4.4 (Mech) Industrial Engine Engine Valve Lash

If the valve lash requires adjustment several times in a short period of time, excessive wear exists in a different part of the engine. Find the problem and make necessary repairs 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:

Fuel injectors that operate incorrectly
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 lash

If the camshaft and the valve lifters show rapid wear, look for fuel in the lubrication oil or dirty lubrication oil as a possible cause.

The valve lash is measured between the top of the valve stem and the rocker arm lever.

Note: An adjustment is not necessary if the measurement of the valve lash is in the acceptable range. Inspect the valve lash while the engine is stopped and when the engine is cold.

Note: When the following procedures are performed, the front housing must be installed.

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Illustration 1	g00323903
Setting the valve lash (1) Adjustment screw (2) Feeler gauge

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Accidental engine starting can cause injury or death to personnel.

To prevent accidental engine starting, turn the ignition switch to the OFF position, place a do not operate tag at the ignition switch location and disconnect and tape the electrical connection to the stop solenoid that is located on the fuel injection pump.

Remove the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove and Install".
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 4 cylinder has opened and the exhaust valve of the No. 4 cylinder has not completely closed measure the valve lash of the inlet valve and the exhaust valve of the No. 1 cylinder. If necessary, make adjustment.
Lightly tap the rocker arm at the top of the adjustment screw with a soft mallet. This will ensure that the lifters are seated against the camshaft.
1. Loosen the valve adjustment screw locknut that is on adjustment screw (1).
2. Place the appropriate feeler gauge (2) between the rocker arm and the valve. Turn adjustment screw (1) while the valve adjustment screw locknut is being held from turning. Adjust the valve lash until the correct specification is achieved.
3. After each adjustment, tighten the valve adjustment screw locknut to a torque of 27 N·m (19.9 lb ft) while adjustment screw (1) is being held.
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 2 cylinder has opened and the exhaust valve of the No. 2 cylinder has not completely closed measure the valve lash of the inlet valve and the exhaust valve of the No. 3 cylinder.
If adjustment is necessary, refer to Steps 2.a, 2.b, and 2.c above.
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 1 cylinder has opened and the exhaust valve of the No. 1 cylinder has not completely closed measure the valve lash of the inlet valve and the exhaust valve of the No. 4 cylinder.
If adjustment is necessary, refer to Steps 2.a, 2.b, and 2.c above.
Rotate the crankshaft in a clockwise direction that is viewed from the front of the engine. When the inlet valve of the No. 3 cylinder has opened and the exhaust valve of the No. 3 cylinder has not completely closed measure the valve lash of the inlet valve and the exhaust valve of the No. 2 cylinder.
If adjustment is necessary, refer to Steps 2.a, 2.b, and 2.c above.
Install the valve mechanism cover. Refer to Disassembly and Assembly, "Valve Mechanism Cover - Remove and Install".