HARNESS AS 6Y4522 - Caterpillar

Initial Inspection of the Fuel System
A problem with the components that send fuel to the engine can cause low fuel pressure. This can decrease engine performance.
Check the fuel level in the fuel tank. Inspect the cap for the fuel tank. Ensure that the vent in the fuel cap is not filled with dirt.
Check all fuel lines for fuel leakage. The fuel lines must be free from restrictions and faulty bends. Verify that the fuel return line is not collapsed.
Clean the screen inside the inlet fitting of the fuel transfer pump.
Operate the hand priming pump (if equipped). If excessive resistance is felt, inspect the fuel pressure regulating valve. Make sure that the pressure regulator is installed correctly, and make sure that the pressure regulator functions correctly.
Install a new fuel filter.
Cut the old filter open with the 175-7546 Oil Filter Cutter Gp. Inspect the filter for excess contamination. Determine the source of the contamination. Make the necessary repairs.
Service the primary fuel filter (if equipped).
Operate the hand priming pump (if equipped). If uneven resistance is felt, test for air in the fuel. Refer to Testing and Adjusting, "Air in Fuel - Test" for more information.
Remove any air that may be in the fuel system. Refer to Testing and Adjusting, "Fuel System - Prime".Inspection of the Fuel System during Engine Operation
Either too much fuel for combustion or not enough fuel for combustion can be the cause of a problem in the fuel system. Finding the source of the problem can be difficult, especially when you have smoke that rises from the exhaust. Therefore, work is often done on the fuel system when the problem is really with some other part of the engine.When noticeable smoke rises from the exhaust, this problem can be caused by a damaged unit injector. This unusual smoke can also be caused by one or more of the reasons that follow:
Not enough air for good combustion
An overload at high altitude
Oil leakage into combustion chamber
Altitude
Air inlet and exhaust leaksNote: Refer to Troubleshooting for more information on the fuel system.Checking The Operation Of Individual Cylinders
Low temperature at an exhaust manifold port is an indication of no fuel to the cylinder. This can possibly be an indication of an injector with a defect. An extra high temperature at an exhaust manifold port can be an indication of too much fuel to the cylinder. High temperatures may also be caused by an injector with a defect.Refer to Testing And Adjusting, "Exhaust Temperature - Test" for the procedure for checking the temperatures in the exhaust manifold port.