TM   5-4930-227-14 Table   5-2.   Repair   and   Replacement   Standards-Continued Manufacturer’s dimensions Desired Component and  tolerances clearance in  inches Min Max Min Max Cylinder to skirt clearance 0.006 0.0065 0.0065 Pin to connecting rod clearance 0.0002 0.0003 0.0008 Tappet to valve clearance (cold) Intake 0.008 Exhaust 0.014 Valve stem to guide clearance 0.003 0,005 0.007 Section Ill. REPAIR PARTS, SPECIAL TOOLS AND 5-5. Special Tools and Equipment repair parts are No special tools or equipment are. required by 4930-227-24P. direct  support  and  general  support  maintenance EQUIPMENT listed and illustrated in TM 5- personnel  for  performing  maintenance  on  the 5-7. Specially Designed (Fabricated) Tools tank  and  pump  unit. and Equipment 5-6. Direct Support and General Support No specially  designed  tools  or  equipment  are  re- Maintenance Repair Parts quired  for  direct  support  and  general  support Direct  support  and  general  support  maintenance maintenance  of  the  tank  and  pump  unit. Section IV. TROUBLESHOOTING 5-8.  General The  corrective  action  recommended  is  described This  section  provides  information  useful  in  diag- opposite  the  probable  cause. nosing  and  correcting  unsatisfactory  operation  or failure  of  the  tank  and  pump  units,  or  any  of 5-9. Direct Support and General Support their components. Each malfunction stated is fol- Maintenance Troubleshooting lowed by a list of probable causes of the trouble. Refer  to  table  5-3. Table   5-3.   Toubleshooting. Malfunction 1. Engine fails to start 2.  Excessive  oil  consumption 3. Knock in engine 4. Engine  smokes  excessively Probable   cause a. b. a. b. c. d. a. b. a. b. Valves or valve seat defective Compression weak Piston rings worn or broken Cylinder wall worn or scored Oil pump not operating effectively Main or connecting rod bearing faulty hose or burned out connecting rod bearing Loose or worn piston pin Piston or rings worn or damaged Cylinder walls scored or worn Corrective    action m. b. a. b. c. d. a. b. a. b. Repair or replace valves or valve seat (para 6-4). Replace piston rings (para 6-6). Replace piston rings (para 6-6). Replace crankcase (para 6-4). Replace damaged oil pump parts (para  6-5). Replace damaged bearings (para 6-4). Overhaul  engine. Replace piston, piston pin and con- necting rod as necessary (para 6–6) . Replace piston or rings (para 6-6). Replace crankcase (para 6-4). 5-2