DETERMINING ENGINE CONDITION

COMBUSTION CHAMBER EFFICIENCY B AFFECTED BY: AIR/FUEL MOVEMENTAIR/FUEL MOVEMENT COMBUSTION TURBULENCECOMBUSTION TURBULENCE INTAKE DESIGNINTAKE DESIGN EGREGR COMBUSTION CHAMBER DESIGNCOMBUSTION CHAMBER DESIGN

MANUAL COMPRESSION TESTING (CYL. SEALING) B EASIEST MANUAL TEST IS A VACUUM TEST B EACH CYLINDER IS A INDIVIDUAL AIR PUMP B THERE MUST BE A GOOD CYLINDER SEAL TO HAVE GOOD VACUUM B ANY CYLINDER LEAK WILL SHOW ON VACUUM GAUGE

VACUUM B Measured in Inches of Mercury (Hg) B A Reduction of 1 inch of vacuum per 1000 feet increase in altitude B Pounds Per Square Inch Absolute (PSIA) B Air moves rapidly from a High pressure to a low pressure C24-25

VACUUM TESTING PROCEDURES B CRANKING VACUUM B IDLE VACUUM B IDLE THROTTLE ANGLE CHECK B 2500 RPM VACUUM B PISTON RING TEST B IDLE/DRIVE TEST B CRUISE TEST B VAC AT W.O.T. AND AFTER W.O.T. L138

TYPICAL VACUUM READINGS B CRANKING VACUUM 3-5” B IDLE VACUUM 18” B IDLE THROTTLE ANGLE 0” B 2500 RPM VACUUM 20” B VAC TEST PROCEDURE CAN IDENTIFY POTENTIAL PROBLEMS B COMPRESSION TEST CAN PINPOINT

COMPRESSION TESTING

READING COMPRESSION GAUGE B 1ST PUFF - SHOULD BE 50% OF FINAL PUFF (INDICATOR OF CYLINDER WALL AND RINGS) B ALL READINGS UNIFORM B IF REAL HIGH - CARBON BUILD-UP B IF CHANGE ON ONE CYL - POSSIBLE STICKING VALVE

COMPRESSION AND VACUUM B BOTH REQUIRE GOOD CYLINDER SEAL B LACK OF CYLINDER SEAL WILL PREVENT PRESSURE TO RISE HIGH ENOUGH TO IGNITE THE MIXTURE B COMPRESSION & VAC TEST INDICATES CYLINDER SEAL, RUNNING COMPRESSION TEST INDICATES VOLUMETRIC EFFICIENCY

CYLINDER BALANCE

MANUAL CYLINDER BALANCE B SHORTING PLUG ONE BY ONE B TIME CONSUMING B DON’T OPEN CIRCUIT SECONDARY CIRCUIT B WILL PINPOINT LOW POWER OUTPUT OF A CYLINDER

OTHER CYLINDER BALANCE TESTS B ELECTRONICALLY PERFORMED BY ENGINE ANALYZER CRANKING TESTCRANKING TEST AMPS PER CYLINDERAMPS PER CYLINDER RELATIVE COMPRESSIONRELATIVE COMPRESSION

CYLINDER CONTRIBUTION B FUEL DISTRIBUTION B DUAL PLANE B SINGLE PLANE B LOW RISE B HIGH RISE

COMPUTER CONTROLLED ENGINE POWER BALANCE B DISCONNECT O2 SENSOR B INITIAL TIMING MODE B DISCONNECT EGR B STABILIZE MAP IF APPLICABLE B STABILIZE FUEL PRESSURE B STABILIZE IDLE CONTROL B PREFERRED TEST RPM RPM

VOLUMETRIC EFFICIENCY

MANUAL TEST OF VOLUMETRIC EFFICIENCY B CAN TEST AT: CRANKINGCRANKING IDLEIDLE SNAP ACCELERATIONSNAP ACCELERATION

CRANKING COMPRESSION TEST B SLOW CRANKSHAFT SPEED/CYLINDER COMPLETELY FILLS/ HIGH COMPRESSION B CHECK OVERALL MECHANICAL CONDITION B CHECKS FOR LEAKS

IDLING COMPRESSION B AIR RESTRICTED BY THROTTLE PLATE B CRANKSHAFT SPEED 4 TO 5 TIMES CRANKING SPEED B LESS AIR ENTERING CYL PER ENGINE CYCLE B TYPICALLY 50 TO 60 PSI CON’T NEXT SLIDE

IDLE TEST, CONT’D B MUST “BURP” GAUGE B IF RPM BROUGHT UP SLOWLY TO 1500 RPM, PRESSURE GOES DOWN TO ABOUT 40 PSI. B NO MANUFACTURER’S SPEC COMPARE WITH OTHER CYLINDERS

SNAP ACCELERATION B QUICKLY SNAP-OPEN THROTTLE, THIS REMOVES THROTTLE PLATE RESTRICTION B READINGS SHOULD INCREASE TO 80% OF CRANKING COMPRESSION B HIGH READING:RESTRICTION IN EXHAUST OR VALVE TRAIN B LOW READINGS: RESTRICTED INTAKE OR CARBON ON VALVE

LAB EXERCISE B VACUUM TESTS B CYLINDER BALANCE SEVERAL METHODSSEVERAL METHODS B RUNNING COMPRESSION TEST