TM 5-3805-260-24Constant bleed valve (4) lets approximately 9 gallons offuel per hour go back to fuel tank (7). This fuel goesback to fuel tank (7) through return line for constantbleed valve (3). This flow of fuel removes air fromhousing (14) and also helps to cool the fuel injectionpump. Check valve (D) makes a restriction in this flow offuel until the pressure in housing (14) is 8 3 psi (55 20 kPa).OPERATION OF FUEL INJECTION PUMPSThe main components of a fuel injection pump in thesleeve metering fuel system are barrel (A), plunger (B),and sleeve (D). Plunger (B) moves up and down insidethe barrel (A) and sleeve (D). Barrel (A) is stationarywhile sleeve (D) is moved up and down on plunger (B) tomake a change in the amount of fuel for injection. Whenthe engine is running, fuel under pressure from the fueltransfer pump goes in the center of plunger (B) throughfuel inlet (C) during the down stroke of plunger (B). Fuelcan not go through fuel outlet (E) at this time because itis stopped by sleeve (D), (see position 1). Fuel injectionstarts (see position 2) when plunger (B) is lifted up inbarrel (A) enough to close fuel inlet (C). There is anincrease in fuel pressure above plunger (B), when theplunger is lifted by camshaft (4). The fuel above plunger(B) is injected in to the engine cylinder.FUEL INJECTION SEQUENCE1, 2, 3. Injection stroke (positions) of a fuelinjection pump. 4. Injection pump camshaft. A.Barrel. B. Plunger. C. Fuel inlet. D. Sleeve. E.Fuel outlet. F. Lifter.Injection will stop (see position 3) when fuel outlet (E) islifted above the top edge of sleeve (D) by camshaft (4).This movement lets the fuel that is above, and In,plunger (B) go through fuel outlet (E) and return to thefuel injection pump housing.When the sleeve (D) is raised on plunger (B), fuel outlet(E) is covered for a longer time, causing more fuel to beinjected in the engine cylinders. If sleeve (D) is low onplunger (B), fuel outlet (F.) is covered for a shorter time,causing less fuel to be injected.OPERATION OF FUEL INJECTION NOZZLEThe fuel inlet (6) and nozzle tip (13)re parts of the nozzlebody, (11). Valve (8) is held in position by spring forceForce of the spring is controlled by pressureadjustment screw (3). Locknut (4-) holds pressureadjustment screw (3) in position. The lift of value (8) iscontrolled 1b lift adjustment screw (2).Locknut (10)holds lift adjustment screw (2) in position. Compressionseal (7) goes on nozzle body (11). The compressionseal goes against inlet fitting (6) and prevents theleakage of compression from the cylinder. Carbon dam(12), at the lower end of nozzle body (11), prevents thedeposit of carbon in the bore in the cylinder head.FUEL INJECTION NOZZLE1. Cap. 2. Lift adjustment screw. 3. Pressureadjustment screw. 4. Locknut for pressureadjustment screw. 5. O-ring seal. 6. Fuel inlet. 7.Compression seal. 8. Valve. 9. Orifices (four). 10.Locknut for lift adjustment screw. 11. Nozzle body.12. Carbon dam. 13. Nozzle tip.Fuel, under high pressure from the fuel injection pumpgoes through the hole in fuel inlet (6). Tile fuel then goesaround valve (8), fills the inside of nozzle body (11) andpushes against the valve guide. When the force madeby the pressure of the fuel is more than the force of thespring, valve (8) will lift. When valve (8) lifts, fuel underlight pressure will go through the four .0128 in. (0.325mm) orifices (9) into the cylinder. When the fuel is sent2-10
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