0335768 JOHNSON PLATE, Rear, 115 models

Illustration 1 g06512544
Fuel injector
(1) Spring
(2) Plunger
(3) Barrel
(4) Solenoid connection to the Electronic Control Module (ECM)
(5) Seal
(6) Fuel supply
(7) Spill valve solenoid
(8) Direct operated check (DOC) solenoid
(9) Spring
(10) Check valve
(11) Spring
(12) Body
(13) Seal
(14) Tip assemblyFuel at low pressure from the fuel supply manifold enters the electronic unit injector at the fill port through drilled passages in the cylinder head.As the electronic unit injector mechanism transfers the force to the top of the electronic unit injector, spring (1) is compressed and plunger (2) is driven downward. This action displaces fuel through the valve in solenoid valve assembly (7), and into the return manifold to the fuel tank. As the plunger travels downward, the passage in barrel (3) is closed by the outside diameter of the plunger. The passages within body (12) and along check valve (10) to the injector tip already contain fuel for injection. After the passage in the plunger barrel is closed, the injector is ready for injection at any time. The start of injection relies on the software in the ECM.The ECM sends a signal to energize solenoid (7), which causes the valve to block the flow of fuel to the fuel return manifold. Fuel pressure is elevated in the injector tip. As the plunger continues to travel downward, the ECM also sends a signal to energize solenoid (9), which controls the direct operated check valve. The direct operated check valve delays the start of injection, and the direct operated check valve increases the valve opening pressure of the injector by equalizing the pressure on both sides of the injector's check valve. Injection begins at 34500 1900 kPa (5000 275 psi) as the direct operated check valve blocks the flow of pressurized fuel to the top side of the injector's check valve, and the force of spring (11) is overcome. The check valve begins to lift from the valve seat. The pressure continues to rise as the plunger continues to travel downward. After the correct amount of fuel has been discharged into the cylinder, the ECM removes the signal to the solenoid connection for the direct operated check valve. The direct operated check valve is returned to the open position. This allows the pressurized fuel and the spring force to overcome the pressurized fuel at the injector tip, which causes the injector's check valve to seat quickly. As the plunger continues through the full stroke, the solenoid valve assembly (7) is de-energized and the valve is returned to the open position by spring (9). The fuel is then dumped through the spill port and into the fuel return manifold. The fuel is then returned to the fuel tank.The duration of injection meters the fuel that is consumed during the fuel injection process. Injection duration is controlled by the governor logic that is programmed into the ECM.As the camshaft lobe rotates past the point of maximum lobe lift, the force on top of the electronic unit injector is removed and the spring for the injector mechanism is allowed to expand. The plunger returns to the original position. This uncovers the fuel supply passage into the plunger barrel to refill the injector pump body. The fuel at low pressure is again allowed to circulate through the fuel injector body. After circulating through the fuel injector body, the fuel flows out of the spill port. This continues until the solenoid valve assembly is re-energized for another injection cycle.