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DETERMINING ENGINE CONDITION

DETERMINING ENGINE CONDITION. COMBUSTION CHAMBER EFFICIENCY . AFFECTED BY: AIR/FUEL MOVEMENT COMBUSTION TURBULENCE INTAKE DESIGN EGR COMBUSTION CHAMBER DESIGN. MANUAL COMPRESSION TESTING (CYL. SEALING). EASIEST MANUAL TEST IS A VACUUM TEST EACH CYLINDER IS A INDIVIDUAL AIR PUMP

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DETERMINING ENGINE CONDITION

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  1. DETERMININGENGINE CONDITION

  2. COMBUSTION CHAMBER EFFICIENCY • AFFECTED BY: • AIR/FUEL MOVEMENT • COMBUSTION TURBULENCE • INTAKE DESIGN • EGR • COMBUSTION CHAMBER DESIGN

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

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

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

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

  7. COMPRESSION TESTING

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

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

  10. CYLINDER BALANCE

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

  12. OTHER CYLINDER BALANCE TESTS • ELECTRONICALLY PERFORMED BY ENGINE ANALYZER • CRANKING TEST • AMPS PER CYLINDER • RELATIVE COMPRESSION

  13. CYLINDER CONTRIBUTION • FUEL DISTRIBUTION • DUAL PLANE • SINGLE PLANE • LOW RISE • HIGH RISE

  14. COMPUTER CONTROLLED ENGINE POWER BALANCE • DISCONNECT O2 SENSOR • INITIAL TIMING MODE • DISCONNECT EGR • STABILIZE MAP IF APPLICABLE • STABILIZE FUEL PRESSURE • STABILIZE IDLE CONTROL • PREFERRED TEST RPM 800-1200 RPM

  15. VOLUMETRIC EFFICIENCY

  16. MANUAL TEST OF VOLUMETRIC EFFICIENCY • CAN TEST AT: • CRANKING • IDLE • SNAP ACCELERATION

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

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

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

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

  21. LAB EXERCISE • VACUUM TESTS • CYLINDER BALANCE • SEVERAL METHODS • RUNNING COMPRESSION TEST

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