0321283 JOHNSON O-RING,Trim cylinder

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.
Keep all parts clean from contaminants.Contaminants may cause rapid wear and shortened component life.
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 Tooling (A) contains several pressure gauges that are used for measuring engine pressures.Reference: Refer 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 restrictionsHigh 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 lineType I Fuel System
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
(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)
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 passa