MISFIRING OR RUNNING ROUGH

ENGINE CRANKSHAFT WILL NOT TURN WHEN START SWITCH IS ON

TM-5-3805-263-14P-2 Grader Heavy Road Motorized Type I Nonsectionalized Type II Sectionalized Manual
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TROUBLESHOOTING TESTING AND ADJUSTING TM 5-3805-263-14&P-2 3. MISFIRING OR RUNNING ROUGH Cause Air In The Fuel System Fuel Pressure is Low Leak or Break in Fuel Line Between Injection Pump and Injection Valve Defect in Fuel Injection Valve(s) or Injection Pump(s) Fuel System Not Timed Correctly to Engine Run engine at rpm that gives maximum misfiring or rough running. Then loosen a fuel line nut on the injection valve for each cylinder, one at a time. Find the cylinder where loosening the fuel line nut does not change the way the engine runs. Test the injection pump and injection valve for that cylinder. Install ‘new parts where needed. Make adjustment to timing if necessary. Wrong Valve Clearance Make adjustment, See the Subject VALVE CLEARANCE in Test- ing and Adjusting. Bent or Broken Push Rod Replacement of push rod is necessary. Worn Valve Seat or Face of Valve Reconditioning of cylinder head is needed. Correction Find air leak in the fuel system and correct. Remove air from fuel system. See FUEL SYSTEM in Testing and Adjusting. Make sure there is fuel in the fuel tank. Look for leaks or bad bends in the fuel line between fuel tank and fuel transfer pump. Look for air in the fuel system. Check fuel pressure at the fuel injection pump housing. If fuel pressure at high idle is lower than 105 kPa (15 psi), install a new filter element. If fuel pressure is still low, check the fuel bypass valve and the check valves in the fuel transfer pump. Install a new fuel line. 4. STALL AT LOW RPM Cause Idle rpm Too Low Correction Make adjustment to governor so idle rpm is the same as given in FUEL SYSTEM, Testing and Adjusting. Defect in Fuel Injection Valve(s) or Fuel Injection Pump(s) Run engine at rpm that gives maximum misfiring or rough running. Then loosen a fuel line nut on the injection pump for each cylinder, one at a time. Find the cylinder where loosening the fuel line nut does not change the way the engine runs. Test the injection pump and injection valve for that cylinder. Install new parts where needed. 1-27

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