. OPERATION TROUBLES AND ACTIONS Problem Main causes Remedy Abnormal noise generated (combustion or mechanical) Low grade fuel being used Overheating Change to specified fuel See "Red range of engine coolant temperature gauge lights up" Replace muffler ( Adjust valve clearance) Damage inside muffler Excessive valve clearance Engine stops while in work Clogging feed pump pre-filter Defective engine and fuel line Replace filter cartridge ( Check, repair) 3 - 140