FUEL SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
AIR IN FUEL TEST
Inspect fuel system for leaks. Replace or repair leaking fuel system components.
Check fuel level in fuel tank (TM 5-3805-291-10).
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Air can enter fuel system on suction sidebetween fuel transfer pump and fuel tank.
When possible, install sight gage in straight sectionof fuel line that is at least 12 in. (304.8 mm)
long. To avoid turbulence, DO NOT install sight gage near elbows, relief valves, and check valves.
Install fluid filter (sight gage tool) in fuel return line.
Observe fuel flow during engine cranking. Check for air bubbles in fuel. If there is no fuel in sight gage, prime fuel sys-
tem (TM 5-3805-291-10).
If engine starts, check for air in fuel at varying engine speeds. If possible, operate engine under conditions known to
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Steady stream of smallbubbles with diameter of approximately 0.063 in. (1.60 mm) is acceptable
amount of air in fuel.
Bubbles with diameter of approxmately 0.250 in. (6.35 mm) are also acceptable if there is a two-
to-three second interval between bubbles.
Excessive air bubbles in fuel are not acceptable.
Observe amount of air in fuel.