Fuel Injection Pump

Bosch single plunger mechanical pump consists of low-pressure, vane-type fuel pump, high-pressure distributor plunger injection pump, centrifugal governor, injection timing mechanism, electrical fuel shut-off solenoid, and manual injection pump shut-off valve. See Fig 1 .

Fig 1: Bosch Diesel Fuel Supply System Illustration applies to all models except Turbo.

As vane pump rotor turns, centrifugal force holds vanes against walls of pump's pressure chamber. Off-center design of rotor and pressure chamber squeezes trapped fuel between vanes and forces it out delivery port. Vane pressure is 42.7-99.6 psi (3-7 kg/cm² ). Main pump increases this pressure to approximately 1800-2400 psi (126-168 kg/cm² ). Pressures vary with model application.

Injection pump on Turbo models is also equipped with boost pressure enrichment device. See Fig 2 . Since turbocharger supplies more air to engine, boost pressure enrichment device is needed to increase amount of fuel delivered to engine.

At full throttle, when turbocharger boost pressure is low, no enrichment is needed. As turbocharger boost pressure increases, pressure begins to work on enrichment device diaphragm, forcing it down. This moves bell crank which in turn moves control ring further to right. Effective stroke of distributor plunger is lengthened and increases amount of fuel delivered to injectors.

Fig 2: Bosch Diesel Fuel Injection Pump Illustration applies to Turbo models only.