Fuel Injection Pump

The Bosch VE type single plunger mechanical pump consists of a low-pressure, vane-type fuel pump, a high-pressure distributor-type plunger injection pump, a centrifugal governor, and an injection timing advance mechanism. Pumps are equipped with an electrical fuel shut-off solenoid. See Figure .

As the vane type pump rotor turns, centrifugal force holds the vanes against the walls of the pump's pressure chamber. The offset design of the rotor and pressure chamber squeezes trapped fuel between vanes and forces it out the delivery port.

The amount of fuel injected is controlled by changing the injection cut-off point according to engine speed and load conditions. The cut-off point is controlled by the position of the metering sleeve around the distributor plunger. The sleeve normally covers a relief port in the plunger. Uncovering the port stops injection.

The sleeve position is determined by a centrifugal governor and the accelerator linkage. A large quantity of fuel is supplied during starting, less at idle. No fuel is allowed to pass when the engine exceeds a predetermined maximum RPM.

The high altitude system advances injection timing to provide a longer burn. This ensures complete combustion and prevents smoky exhaust. Injection timing is advanced by the action of a solenoid valve mounted on the side of the injection pump. Solenoid action is controlled by a micro switch attached to an aneroid bellows. The bellows expands at altitudes above 3000 feet and opens the micro switch. Opening this switch deactivates the solenoid.