101603-2341 ZEXEL 9 400 611 255 BOSCH INJECTION-PUMP ASSEMBLY 9400611255 1016032341 220204910a

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