42979 Mercury NUT, FLYWHEEL

Engine Will Not Start Step 1
Install the Electronic Control Analyzer and Programmer (ECAP) or the Digital Diagnostic Service Tool (DDT). See Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.Step 2
Electronic Self Check. Check the electronics diagnostic lamp on the dash to determine if there are any faults in the engine electronics system. Repair or replace parts as needed. Refer to Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.Step 3
Check Cranking Speed Of Crankshaft. Using the ECAP or DDT, check the speed of the crankshaft while the starter is cranking. If the crankshaft speed is below 250 rpm, then proceed to item 4. If the crankshaft speed is above 250 rpm, then proceed to item 5.Step 4
Possible Causes Of Low Cranking Speed:1. Low Battery VoltageCheck battery voltage. If the voltage is less than 8 volts for a 12 volt system, or 16 volts for a 24 volt system, put a charge to the battery. If the battery will not hold a charge, load test the battery. Use the 6V4930 Battery Load Tester and make reference to Special Instruction, Form No. SEHS8268 for complete information on use of the 6V4930 Battery Load Tester.2. Defective Cable, Battery To Starter, Or Defective ConnectionWith ignition switch in the START position, check the voltage at the connection of the battery cable to the starter. If there is no voltage, or if the voltage is low at this connection and there is good voltage at the battery, check for a defective cable or connection between the battery and the starter.3. Oil Too Thick For Free Crankshaft RotationRefer to the 3176 Truck Engine Operation And Maintenance Manual, Form No. SEBU6163 for the correct SAE grade oils for the ambient temperatures at which the engine is being operated. At temperatures below -23° C (-10° F), it may be necessary to warm the oil for free crankshaft rotation.4. Defective Starter MotorRemove and test. Make repairs as necessary or install a new starter motor.5. Extra Outside Loads.Damage to the power take-off equipment (if so equipped) and/or transmission can put extra load on the engine and prevent free rotation of the crankshaft. To check, disconnect the transmission and power takeoff, and start the engine.6. Transmission Or Power Take-off ProblemSee the Truck Manufacturer's Service Manual.7. Internal Engine ProblemDisassemble the engine and check all components for damage. See 3176 Diesel Truck Engine Disassembly And Assembly, Form No. SENR3914.Step 5
Can Exhaust Smoke Be Seen While Starting?If exhaust smoke can be seen while starting the engine, then proceed to item 6. If exhaust cannot be seen while starting the engine, then proceed to item 7.Step 6
A. Possible Causes-Engine Will Not StartCold Outside TemperaturesIt may be necessary to use starting aids, or to heat engine oil or coolant at temperatures below 0° C (32° F).B. Air In Fuel SystemWith air in the fuel system, the engine will normally be difficult to start, run rough, and release a large amount of white smoke. If the engine will not start, loosen the highest drain plug on the front end of the fuel manifold. Operate the fuel priming pump until the flow of fuel from the loosened drain plug is free of air. Tighten the drain plug. If the air cannot be removed in this way, put 35 kPa (5 psi) of air pressure to the fuel tank.
Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.
Check for leaks at the connections between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the lines. If there are no visual leaks, remove the fuel supply line from the tank and connect it to an outside fuel supply. If this corrects the problem, the suction line (standpipe) inside the fuel tank has a leak.C. Poor Quality FuelRemove a small amount of fuel from the tank and check for water or other contamination in the fuel. See Special Instruction, Form No. SEHS7067 for complete information on fuel recommendations for Caterpillar diesel engines. If there is water in the fuel, remove the fuel until it is free of water. Fill with good quality fuel. Change the fuel filter and prime the system using the fuel priming pump. If there is water in the fuel, use an outside source of good quality fuel, prime and start the engine. If the engine starts easily, remove all the fuel from the fuel tank and fill with good quality fuel. Prime the fuel system if necessary.D. Low Fuel PressureChange the fuel filter. If the pressure remains low, check the by-pass valve in the fuel transfer pump and the fuel pressure regulating valve in the fuel manifold adapter. Debris in the system can cause the valves to remain in the open position.E. Fuel Injection Timing Out Of CalibrationCheck the fuel injection timing calibration and make necessary adjustments. See the topics, Engine Test Procedure Number P-402, [Checking Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)], and Engine Test Procedure Number P-403, [Calibrating Electronic Injection Timing With The Timing Adapter Tool Group And The ECAP (Electronic Control Analyzer and Programmer)], in Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913.F. Valve Adjustment Not CorrectCheck and make necessary adjustments. See the topic, Valve Clearance Setting, in 3176 Diesel Truck Engine Systems Operation And Testing and Adjusting, Form No. SENR3909. Intake valve clearance is 0.38 mm (.015 in), and exhaust valve clearance is 0.64 mm (.025 in). Also check for bent or broken push rod or other valve train parts.G. Defective Unit Injector(s)Find a defective unit injector by running the engine at the rpm where it runs rough. Use the Electronic Control Analyzer and Programmer (ECAP) service tool single cylinder cutout procedure (see Electronic Troubleshooting, 3176 Diesel Truck Engine, Form No. SENR3913) to stop the fuel supply to each cylinder. If a cylinder is found where the cutout makes no difference on the rough running, drain the fuel supply