BOLT 4471721 - Caterpillar

Table 1
Required Tools
Part Number Part Description Qty
2P-8278 Fuel Flow Tube (Sight Gauge) 1 This procedure checks for air in the fuel system. This procedure also helps with 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.
Work carefully around an engine that is running. Engine parts that are hot, or parts that are moving, can cause personal injury.
Install a 2P-8278 Fuel Flow Tube (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 inches) 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 that is present in the sight gauge, prime the fuel system. Refer to Operation and Maintenance Manual, "Fuel System Priming Pump - Operate" 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.
Illustration 1 g00578151
2P-8278 Fuel Flow Tube (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 two seconds to three 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 inlet