ENGINE AR-PRIMARY 3305456 - Caterpillar

Table 1
Tools Needed
Part Number Description 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 that there is a problem with lubrication:
Excessive carbon deposits
Failed or broken valves
Stuck or broken piston rings
Worn piston rings
Worn cylinder linersMeasure the cylinder pressure of an engine after approximately 250 hours of operation. Record the data. Continue to measure the cylinder pressures periodically. Comparing the recorded data to the new data provides information about the condition of the engine.Note: Cylinder pressure is one of the factors that help to determine the overhaul interval. Refer to the Operation and Maintenance Manual for your engine for details.If the cylinder pressure has risen by one or more compression ratios, the engine needs a top end overhaul in order to remove carbon 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 strategy will enable a maximum consistent cranking speed for the check. Also, the battery power will be conserved.Illustration 1 is a graph of approximate cylinder pressures for engines with different compression ratios. Use this chart for reference.
Illustration 1 g02417877
Chart of approximate cylinder pressures for gas engines