TIGHTENING HIGH PRESSURE FUEL PIPE NUTS

Fig. 11 (d) Later Fuel Pump - TM-55-1930-209-14P-9-4_625

TM-55-1930-209-14P-9-4 Water Purification Barges (NSN 1930-01-234-2165) Electric Power System Manual
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Bleeding the Thermostart: The Mark Ill device incorporates a heat sensitive bi-metallic element to open and close the fuel inlet valve. If the device is used "dry" (i.e., without fuel) the bi-metallic element will become distorted because of the excessive heat and thereafter will not function properly to shut off the fuel. The result of unmetered fuel entering the combustion chambers will be difficult starting, black exhaust smoke and additional engine noise. Also, it can cause hydraulic lockup, which can, in turn, cause the connecting rods to be bent. In consideration of the consequences described above, it is imperative that before attempting to start a new engine or an engine having any part of its low pressure fuel system dismantled, the fuel system and the fuel line to the Thermostart device must be "bled" to ensure fuel availability. To "bleed" the fuel system- 1. Loosen the air vent screw on the injection pump governor control housing. 2. Loosen the hydraulic head vent screw on the side of the injection pump body. 3. Loosen the vent plug on the top of the primary fuel filter. 4. Operate the fuel transfer pump priming lever until fuel free from air bubbles issues from each venting location. While continuing to operate the lever, tighten the screws in the following order. a) Primary fuel filter vent screw. b) Hydraulic head vent screw. c) Governor vent screw. 5. Loosen the fuel line connection at the inlet to the Thermostart device. 6. Operate the fuel lift pump priming lever until fuel free from air bubbles issues from the loosened connection. While continuing to operate the lever, tighten the connection. INJECTOR TESTING AND REPLACEMENT Normally, defective injectors can be isolated by loosening the pipe union nut on each injector in turn while the engine is running at approximately 800 rpm. As each nut is loosened, fuel will not be injected into the associated cylinder and, as a result, the engine rpm will decrease if the injector was previously functioning normally. If the engine rpm remains constant, the injector is probably defective. When installing a replacement injector remember to also include a new copper seating washer. These are special washers and ordinary washers can not be used for this purpose. The recess in the cylinder head, the faces of the washer and the corresponding face of the nozzle holder cap must be perfectly clean to ensure a leak proof seal. The importance of injectors being seated squarely and secured with the correct torque cannot be emphasized too strongly. Even a slight "canting" of the injector can result in fouling and distortion of the nozzle and needle valve. This canting can also result in leakage between injector and cylinder head, with a resultant engine mis-fire. TORQUE - To ensure squareness and free entry of the nozzle into its bore, the securing nuts must be tightened evenly until a torque of 12 Ibf ft (1.7 kgf m) is attained. Overtightening of these securing nuts can result in a fractured injector flange and/or a fouled nozzle needle valve. TIGHTENING HIGH PRESSURE FUEL PIPE NUTS Fuel leakage from high pressure pipe unions will result if the nuts are over-tightened. Excessive torque can cause the ferrule (olive) and/or the collar of the nut to be damaged. The correct torque is 12/15 Ibf ft. (1.7 - 2.0 kgf m) If a high pressure pipe union leaks fuel because the nut has not been tightened sufficiently, the nut should only be tightened enough to stop the leak. -53-

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