90883 Force SCREW (M5 X 16)-SPECIAL

Air in Fuel - Test
This procedure checks for air in the fuel. This procedure also assists in finding the source of the air.
Examine the fuel system for leaks. Ensure that the fuel line fittings are properly tightened. Check the fuel level in the fuel tank. Air can enter the fuel system on the suction side between the fuel transfer pump and the fuel tank.
Install a 2P-8278 Tube As (SIGHT GAUGE) in the fuel return line. When possible, install the sight gauge in a straight section of the fuel line that is at least 304.8 mm (12 inch) long. Do not install the sight gauge near the following devices that create turbulence:
Elbows
Relief valves
Check valvesObserve the fuel flow during engine cranking. Look for air bubbles in the fuel. If there is no fuel in the sight gauge, prime the fuel system. Refer to Operation and Maintenance Manual , "Fuel System - Prime" for more information. If the engine starts, check for air in the fuel at varying engine speeds. When possible, operate the engine under the conditions which have been suspect of air in the fuel.
Illustration 1 g01096678
2P-8278 Tube As (SIGHT GAUGE)
(1) A steady stream of small bubbles with a diameter of approximately 1.60 mm (0.063 inch) is an acceptable amount of air in the fuel.
(2) Bubbles with a diameter of approximately 6.35 mm (0.250 inch) are also acceptable if there is 2 to 3 seconds intervals between bubbles.
(3) Excessive air bubbles in the fuel are not acceptable.
If excessive air is seen in the sight gauge in the fuel return line, install a second sight gauge at the fuel transfer pump inlet. If a second sight gauge is not available, move the sight gauge from the fuel return line to the fuel transfer pump inlet. Observe the fuel flow during engine cranking. Look for air bubbles in the fuel. If the engine starts, check for air in the fuel at varying engine speeds. If excessive air is not seen at the inlet to the fuel transfer pump, the air is entering the system after the fuel transfer pump. Proceed to Step 6.If excessive air is seen at the inlet to the fuel transfer pump, air is entering through the suction side of the fuel system. Proceed to Step 4.
To avoid personal injury, always wear eye and face protection when using pressurized air.
To avoid damage, do not use more than 55 kPa (8 psi) to pressurize the fuel tank.
Pressurize the fuel tank to 35 kPa (5 psi). Do not use more than 55 kPa (8 psi) in order to avoid damage to the fuel tank. Check for leaks in the fuel lines between the fuel tank and the fuel transfer pump. Repair any leaks that are found.
If the source of the air is not found, disconnect the supply line from the fuel tank. Then, connect an external fuel supply to the fuel transfer pump inlet. If connecting an external fuel supply corrects the problem, repair the fuel tank or the stand pipe in the fuel tank.
If the injector sleeve is worn or damaged, combustion gases may be leaking into the fuel system. Also, if the O-rings on the injector sleeves are worn, missing, or damaged, combustion gases may leak into the fuel system. Fuel Quality - Test
This test checks for problems regarding fuel quality. Refer to Diesel Fuels and Your Engine, SEBD0717 for additional details. Use the following procedure to test for problems regarding fuel quality:
Determine if water and/or contaminants are present in the fuel. Check the water separator (if equipped). If a water separator is not present, proceed to Step 2. Drain the water separator, if necessary. A full fuel tank minimizes the potential for overnight condensation. Note: A water separator can appear to be full of fuel when the water separator is full of water.
Determine if contaminants are present in the fuel. Remove a sample of fuel from the bottom of the fuel tank. Visually inspect the fuel sample for contaminants. The color of the fuel is not necessarily an indication of fuel quality. However, fuel that is black, brown, and/or similar to sludge can be an indication of the growth of bacteria or oil contamination. In cold temperatures, cloudy fuel indicates that the fuel may not be suitable for operating conditions. The following methods can be used to prevent wax from clogging the fuel filter:
Fuel heaters
Blending fuel with additives
Utilizing fuel with a low cloud point such as keroseneRefer to Operation and Maintenance Manual, SEBU6251, "Caterpillar Commercial Diesel Engine Fluids Recommendations", "Fuel Recommendations" for more information.
Check fuel API with a 9U-7840 Fluid and Fuel Calibration Gp for low-power complaints. The acceptable range of the fuel API is 30 to 45 when the API is measured at 15 °C (60 °F), but there is a significant difference in energy within this range. Refer to Tool Operating Manual, NEHS0607, for API correction factors when a low-power problem is present and API is high.
If fuel quality is still suspected as a possible cause to problems regarding engine performance, disconnect the fuel inlet line, and temporarily operate the engine from a separate source of fuel that is known to be good. This procedure will determine if the problem is caused by fuel quality. If fuel quality is determined to be the problem, drain the fuel system and replace the fuel filters. Engine performance can be affected by the following characteristics:
Cetane number of the fuel
Air in the fuel
Other fuel characteristicsFuel System Inspection
A problem with the components that send fuel to the engine can cause low fuel pressure. This low fuel pressure can decrease engine performance.
Check the fuel level in the fuel tank. Check the vent in the cap for the fuel tank for dirt.
Check the fuel lines for fuel leakage. Check the fuel lines for a worn bend or a restriction. Check that the fuel return line has not collapsed within the sections that are exposed to heat.
Install a new fuel filter. Clean the primary fuel filter.
To remove air from the fuel system,