812650016 Mercury MAIN NOZZLE

1. Poor Quality Fuel If poor or low quality fuel is suspected, use a source of known good quality fuel, prime and start the engine. If the problem is resolved, drain the complete fuel system, replace the fuel filter, and add fuel recommended by Caterpillar.2. Low Fuel Pressure Measure the fuel transfer pump pressure at rated engine rpm. The 1U5470 Engine Pressure Group can be used to measure the fuel transfer pump pressure. The 1U5470 Engine Pressure Group has a gauge to read fuel pressure to the fuel supply manifold. Special Instruction, Form No. SEHS8907 is with the tool group and gives information for its use. The ECAP or the DDT can also be used to check the fuel transfer pump pressure.If the fuel transfer pump pressure is below 445 kPa (65 psi) at rated rpm, check for: * Restrictions in the low pressure fuel system (plugged fuel filter, collapsed hoses, etc).* Air in the fuel.* Fuel transfer pump wear or damage. Refer to Specifications, 3176 Vehicular Diesel Engine, Form No. SENR4965.* Excessive fuel return to the tank due to a malfunction of the fuel pressure regulating valve in the siphon block.3. Air In Fuel System Disconnect the fuel return line at the tank. Place this end of the line in a container of fuel to see if air bubbles are present while the engine is running. If air bubbles are observed, check for loose fittings or line leaks between the fuel tank and the fuel transfer pump. If leaks are found, tighten the connections or replace the line(s).To remove air from the engine fuel system: With the engine off, loosen the fuel return line fitting at the fuel manifold. Operate the fuel priming pump until the flow of fuel is free of air. Tighten the return line fitting, fasten the priming pump, and start the engine. If the engine still does not run smooth or produces a lot of white smoke, apply 35 kPa (5 psi) of air pressure to the fuel tank to force fuel through the system.
Do not use more than 55 kPa (8 psi) of air pressure in the fuel tank or damage to the tank may result.
Check the fuel return line for restriction. Replace if it is plugged.4. Injector Not Seated Properly Leakage due to a loose injector or inadequate injector/sleeve sealing can cause combustion gas to enter the fuel supply manifold. Inspect and repair as necessary the sealing surface (seat) of the injector sleeve. The injector sealing surface (seat) must be free of scratches or evidence of a combustion leak (carbon). If it is necessary to rework (ream) or replace the sleeve use 4C4054 Tool Group and refer to Special Instruction, Form No. SEHS9246, Using The 4C4054 Unit Injector Sleeve Replacement Tool Group. Torque the fuel injector hold down bolt to 30 7 N m (22 5 lb ft).5. Defective Unit Injectors A defective unit injector can be found using the Electronic Control Analyzer and Programmer (ECAP) and the timing adapter tool group. Run the engine at the rpm where the problem exists. Use the Interactive Diagnostics feature (single cylinder cutout) to stop the fuel supply to each cylinder in turn (see Electronic Troubleshooting, 3176 Vehicular Diesel Engine, Form No. SENR5137). If a cylinder is found where the cutout makes no difference on the engine performance or does not increase the length of the injection duration bars for the other cylinders, that injector should be removed and tested. Drain the fuel supply manifold and remove the injector(s) (see 3176 Vehicular Diesel Engine Disassembly and Assembly, Form No. SENR4965).Testing of the injectors must be done off of the engine. Use the 1U6661 Pop (Injector) Tester Group with a 1U6663 Injector Holding Block, and a 1U6665 Power Supply, to test the injectors. For the test procedure refer to Special Instruction, Form No. SEHS8867, Using The 1U6661 Pop (Injector) Tester. For test specifications refer to Special Instruction, Form No. SEHS8804, Unit Injector Test Specifications for 1.7 Liter Engines. Inspect and repair as necessary the sealing surface (seat) of the injector sleeve in the cylinder head when removing and installing an injector. The injector sealing surface (seat) must be free of scratches or evidence of combustion products. If it is necessary to rework (ream) or replace the sleeve use 4C4054 Tool Group and refer to Special Instruction, Form No. SEHS9246, Using The 4C4054 Unit Injector Sleeve Replacement Tool Group.The diagnostic lamp on the dash can be used to determine if there are any electronic system faults relating to the injectors. Fault codes 72, 73 and 74 relate to the injector operation and wiring. See Electronic Troubleshooting, 3176 Vehicular Diesel Engine, Form No. SENR5137.6. Fuel Injection Timing Not Correct Check the fuel injection timing calibration and make necessary calibrations. See Engine Test Procedure Number P-301 in Electronic Troubleshooting, 3176 Vehicular Diesel Engine, Form No. SENR5137.7. Valve Adjustment Not Correct Check and make necessary adjustments. See the topic, Valve Clearance Setting, in 3176 Vehicular Diesel Engine Systems Operation And Testing and Adjusting, Form No. SENR4964. 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.8. Electronic System Malfunction Use ECAP or DDT to determine if there are any fault codes. See Electronic Troubleshooting, 3176 Vehicular Diesel Engine, Form No. SENR5137. If faults are found, follow the procedures to identify and correct the faults. If no faults are found refer to Engine Test Procedure Number P-103 in Electronic Troubleshooting, 3176 Vehicular Diesel Engine, Form No. SENR5137.9. Cylinder Head Gasket Leakage A defective head gasket can allow combustion gases to leak to: * The exterior of the engine and can be visually detected.* A coolant passage resulting in combustion gas in the coolant. This could cause a coolant loss through the radiator overflow. Remove the radiator filler cap, with the engine running, and check for air bubbles in the coolant caused by exhaust gases.
Do not loosen the filler