Section 2 DIAGNOSTIC ANALYSIS - DEFINITION - Diagnostic   analysis   involved   certain   checks   that   are simple   and   easily   performed.      These   checks   usually reveal  the  most  frequently  encountered  causes  of  faulty operation.    The  data  obtained  must  be  related  to  the complaint.  A failure may be due to a chain of conditions that  no  one  thought  important  enough  to  report.    The repair must include the discovery of the true cause of the complaint   and   the   corrective   measures   necessary   to correct the condition. The  key  to  successful  diagnostic  analysis  is  the  mental matching   of   the   information   of   the   condition   with   a complete   knowledge    of    how    the    engine    and    all    its components operate and their inter-relationship. DIAGNOSTIC ANALYSIS PROCEDURES FOR .  .  .  OIL CONSUMPTION When analyzing a lube oil consumption problem proceed as follows: 1. Visually inspect for external leaks and correct. 2. Check   for   air   cleaner   restriction,   air   induction system leaks and excessive crankcase pressure as specified in Section 5. NOTE  :    On  turbocharged  engines,  change  oil  filter elements   and   inspect   for   turbocharger   damage   if lube oil is drawn into the engine. If items 1 and 2 are NOT the cause, continue analysis. 3. Verify the Problem - a. Change   the   oil   (using   the   recommended API Specification and viscosity for the ambient temperature).  See NOTE. b. Determine  initial  oil  consumption  rate  and trend at 1000 miles/50 hours or 5000 miles/250 hours c. Record   the   amount   of   make   up   lube   oil added during the test period. NOTE:    Verify  engine  is  equipped  with  proper  dip- stick.        Wrong    dipstick    may    result    in    erroneous reading. 4. If oil consumption was excessive, determine the cause of the problem. a. Abnormally    heavy    loads    pulled    by     the vehicle.  (Above the specified GVW). b. Improper operation (i.e.  allowing the engine to lug in the incorrect gear range) resulting in oil consumption. c. Plugged air cleaner element causes high in- take vacuum which will pull over oil through the crankcase breather tube. (Clean element). d. Plugged crankcase breather element. (Clean element) . e. Faulty air compressor.(If compressor piston  rings  are  worn,  oil  can  leak  into  the air system). f. Worn engine valve guides.  (Clean, inspect and replace if required). g. Worn rings and/or bores due to dirt passing air cleaner. .  .  .  FUEL CONSUMPTION 1. When excessive fuel consumption is suspected, verify the problem. a. Compare  the  actual  rate  of  consumption  in gallons per hour or miles per gallon against normal    expected    fuel    usage    in    subject vehicle. b. If  excessive  fuel  consumption  is  confirmed determine the cause of the problem. 2. Check entire fuel system (tank to injection pump) for leaks. 3. Investigate possibility that engine is not in proper specs for the application by conducting diagnostic tests indicated in text. 4. Review   driver’s   habits   to   be   sure   he   is   not lugging or overspeeding engine. 5. Inspect engine per the "PERFORMANCE DATA GUIDELINES"    in    the    rear    of    each    Engine Section for the particular application. CGES-2404 Printed in United States of America Page 1