Page 1 of 7 Shutdown SIS Previous Screen Welcome: sso064204 Product: TRUCK ENGINE Model: C7 TRUCK ENGINE WAX Configuration: C7 On-highway Engine WAX00001-UP Testing and Adjusting C7 On-highway Engine Media Number -RENR7572-06 Publication Date -01/07/2006 Date Updated -25/07/2006 i02917932 Fuel System Pressure - Test SMCS - 1250-081; 1256-081 Table 1 Required Tools Tool Part Number Part Name Qty A 1u-5470 or 198-4240 Engine Pressure Group or Digital Pressure Indicator 1 B 3Y-2888 Connector 1 C 3J-1907 O-Ring Seal 1 Use Tooling (A) in order to check the engine's fuel pressures. Note: It may be necessary to use Tooling (B) and (C) in order to adapt to the correct fitting size. Fuel leaked or spilled onto hot surfaces or electrical components can cause a fire. Clean up fuel spills immediately. NOTICE Keep all parts clean from contaminants.
Page 2 of 7 Contaminants may cause rapid wear and shortened component life. NOTICE Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. Illustration 1 g01450847 1U-5470 Engine Pressure Group (1) Pressure indicator (2) Zero adjustment screw (3) Pressure indicators (4) Pressure tap (5) Pressure indicator
Page 3 of 7 Tooling (A) contains several pressure gauges that are used for measuring engine pressures. ReferenceRefer to Special Instruction, SEHS8907 for information that relates to the operation and maintenance of the tool group. Low Fuel Pressure Low fuel pressure can cause low engine power. Low fuel pressure can also cause cavitation of the fuel which can damage the fuel injectors. The following conditions can cause low fuel pressure: Plugged fuel filters Debris in the check valves for the fuel priming pump (if equipped) Sticking or worn fuel pressure regulating valve in the fuel transfer pump Severe wear on return fuel pressure regulating valve at the rear of the cylinder head Worn gears in the fuel transfer pump Pinched fuel lines or undersized fuel lines Old fuel lines that have a reduced interior diameter that was caused by swelling Fuel lines with deteriorating interior surfaces Pinched fuel line fittings or undersized fuel line fittings Debris in the fuel tank, fuel lines, or fuel system components that create restrictions High Fuel Pressure Excessive fuel pressure can cause fuel filter gaskets to rupture. The following conditions can cause high fuel pressure: Plugged orifices in the fuel pressure regulating valve Stuck fuel pressure relief valve in the fuel transfer pump Restricted fuel return line Type I Fuel System
Page 4 of 7 Illustration 2 g01450864 Fuel lines group (typical example) (6) Tube assembly (fuel transfer pump to fuel filter) (7) Tube assembly (fuel filter to fuel supply passage) (8) Pressure regulator Illustration 3 g01450868 Pressure tap locations (typical example) (9) Fuel filter base (10) Tap for the unfiltered fuel pressure
Page 5 of 7 (11) Tap for the filtered fuel pressure Type II Fuel System Illustration 4 g01450882 Fuel lines group (typical example) (8) Pressure regulator (12) Fuel hose (fuel transfer pump to fuel filter) (13) Tube assembly (fuel filter to fuel supply passage)
Page 6 of 7 Illustration 5 g01450885 Pressure tap locations (typical example) (9) Fuel filter base (11) Tap for the filtered fuel pressure (14) Line for the unfiltered fuel pressure During normal operating conditions and load conditions, the fuel system should maintain the following pressure: 400 to 525 kpa (58 to 76 psi) At low idle, the fuel system should maintain the following pressure: 400 to 435 kpa (58 to 63 psi) The pressure differential is the difference between filtered fuel pressure and unfiltered fuel pressure. With a new filter, the pressure differential across the fuel filter will be the following amount: 35 kpa (5 psi) As abrasive particles collect in the fuel filter, the pressure differential across the filter will increase. When a filter becomes plugged, fuel supply pressure may drop as low as 69 kpa (10 psi) before a significant power loss is detected by the operator. Low fuel pressure will cause cavitation and internal damage to the unit injectors. The pressure differential across the fuel filter should not exceed 69 kpa (10 psi). Pressure regulator (8) is mounted directly in the rear of the cylinder head. The regulator is located at the fuel return port toward the rear end of the fuel supply passage. The orifice maintains fuel pressure at low engine rpm. The regulator contains a check valve that prevents fuel from draining out of the cylinder head and back to the tank during engine shutdown. In order to check the unfiltered fuel pressure (fuel transfer pump pressure), follow this procedure: 1. Install the pressure test group onto the engine. a. For type I fuel systems that contain a fuel pressure tap (10) that is installed in the inlet port of the fuel filter base, remove the plug from the pressure tap. Install Tooling (B) and Tooling (C) on the fuel pressure tap (10). Install Tooling (A) in order to measure the fuel pressure. b. For type II fuel systems without a pressure tap, install a t-fitting in the fuel line for the unfiltered fuel pressure (14). If necessary, install Tooling (B) and Tooling (C) on the t -fitting. Install Tooling (A) in order to measure the fuel pressure. 2. Start the engine and record the unfiltered fuel pressure. To check the filtered fuel pressure, follow these steps:
Page 7 of 7 1. Remove the plug from fuel pressure tap (11). 2. Install Tooling (B), and Tooling (C) to fuel pressure tap (11). Note: Install Tooling (A) in order to measure the fuel pressure. 3. Start the engine and record the unfiltered fuel pressure. Tests for the HEUI Fuel System Injection Actuation Pressure Control System ReferenceRefer to Troubleshooting, "Injection Actuation Pressure Control Valve Circuit - Test" in order to test for the correct operation of the injection actuation pressure control system. ReferenceRefer to Troubleshooting, "Injection Actuation Pressure Sensor - Test" in order to test for the correct operation of the injection actuation pressure sensor. Unit Injector Hydraulic Pump ReferenceRefer to Troubleshooting, "Injection Actuation Pressure - Test" in order to test the unit injector hydraulic pump for problems that relate to mechanical operation and hydraulic operation. Copyright 1993-2013 Caterpillar Inc. All Rights Reserved. Private Network For SIS Licensees. Tue Oct 8 19:35:34 PDT 2013 sso064204