3. Troubleshooting1203.4 Troubleshooting bymeasuring compressionpressureCompression pressure drop is one of major causesof increasing blowby gas (lubricating oil contamina-tion or increased lubricating oil consumption as aresultant phenomenon) or starting failure. The com-pression pressure is affected by the following factors:1) Degree of clearance between piston andcylinder.2) Degree of clearance at intake/exhaust valveseat.3) Gas leak from nozzle gasket or cylinder headgasket.In other words, the pressure drops due toincreased parts wear and reduced durabilityresulting from long use of the engine.A pressure drop may also be caused by scratchedcylinder or piston by dust entrance from the dirtyair cleaner element or worn or broken piston ring.Measure the compression pressure to diagnosepresence of any abnormality in the engine.(1) Compression pressure measurementmethod1) After warming up the engine, remove the fuelinjection pipe and valves from the cylinder tobe measured.2) Crank the engine before installing thecompression gage adapter.a) Perform cranking with the stop handle at thestop position (no injection state).b) See 4.2.3(2) in Chapter 4 for thecompression gage and compression gageadapter.3) Install the compression gage andcompression gage adapter at the cylinder tobe measured.a) Never forget to install a gasket at the tip endof the adapter.4) With the engine set to the same state as in2)a), crank the engine by the starter motoruntil the compression gage reading isstabilized.(2) Standard compression pressureEngine compression pressure list (reference value)ModelCompression pressure at 250 min-1MPa (kgf/cm 2 ) Deviation among cylindersMPa (kgf/cm 2 )Standard3JH4E/ 4JH4E/ 4JH4-TE 3.4 ± 0.1 (35 ± 1) 0.2 to 0.3 (2 to 3)4JH4-HTE 3.2 ± 0.1 (32 ± 1)Compressiongage010638-00SE
