VALVE 4667877 - Caterpillar

Table 1
Tools Needed Quantity
193-5859 Cylinder Pressure Gauge Gp (Gas Engine) 1 Cylinder pressure can be measured during inspection of the spark plugs. The condition of the following items can be tested by checking the cylinder pressure: valves, valve seats, pistons, piston rings and cylinder liners.A loss of cylinder pressure or a change of pressure in one or more cylinders may indicate the following conditions. These conditions may indicate a problem with lubrication:
Excessive deposits
Guttering of valves
A broken valve
A piston ring that sticks
A broken piston ring
Worn piston rings
Worn cylinder linersMeasure the cylinder pressure of an engine after approximately 250 hours of operation. Record the data. Continue to periodically measure the cylinder pressure. Comparing the recorded data to the new data provides information about the condition of the engine.Note: Cylinder pressure is one of the three factors that help to determine the in-frame overhaul interval. Refer to Operation and Maintenance Manual, "Overhaul (In-Frame)".If the cylinder pressure has risen by one or more compression ratios, the engine needs a top end overhaul in order to remove deposits. Failure to remove the deposits will increase the chance for detonation. Severe guttering of the valves will occur.To measure the cylinder pressure, use the 193-5859 Cylinder Pressure Gauge Gp (Gas Engine). Use the Special Instruction, NEHS0798 that is included with the gauge. Use the following guidelines:
Remove all of the spark plugs.
Fully open the throttle plate.
Minimize the cranking time. This will enable a maximum consistent cranking speed for the check. Also, the battery power will be conserved.Illustration 1 is a graph of typical cylinder pressures for engines with different compression ratios.
Illustration 1 g00828960
(Y) Cylinder pressure in kPa
(X) Compression ratio
(1) Normal range for cylinder pressure