SUDDEN CHANGES IN ENGINE SPEED (rpm)

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 5. SUDDEN CHANGES IN ENGINE SPEED (rpm) Cause Failure of Governor or Fuel Injection Pump Correction Look for damaged or broken springs, linkage or other parts. Remove the governor. Check for free travel of the fuel rack. Be sure fuel injection pumps are installed correctly. Check for correct governor spring. Install new parts for those that have damage or defects. Cause Air In The Fuel System Fuel Pressure Is Low Bad Quality Fuel Constant Bleed Valve Stays Open or Closed Leaks in Air Inlet System Governor Linkage Wrong Valve Clearance Defect in Fuel Injection Valve(s) or Fuel Injection Pump(s) Wrong Fuel Injection Timing Rack Setting Too Low Turbocharger Has Carbon Deposits or Other Causes of Friction 6. NOT ENOUGH POWER 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 fuel filter element. If fuel pressure is still low, check the fuel bypass valve and the check valves in the fuel transfer pump. Remove the fuel from the fuel tank. Install a new fuel filter element. Put a good grade of clean fuel in the fuel tank. Install new parts if needed. Check the pressure in the air inlet manifold. Look for restrictions in the air cleaner. Make adjustment to get full travel of linkage. Install new parts for those that have damage or defects. Make adjustment, See the Subject VALVE CLEARANCE in Test- ing and Adjusting. 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. Make adjustment to timing. Make reference to FUEL SYSTEM in Testing and Adjusting. Make inspection and repair of turbocharger as necessary. 1-28

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