HYDRAULIC STARTING SYSTEM (HYDROSTARTER)
The hydrostarter system schematically illustrated in Fig. 6 is a complete hydraulic system for starting internal
combustion engines. The system is automatically recharged after each start, and can be manually recharged. The
starting potential remains during long periods of inactivity, and continuous exposure to hot or cold climates has no
detrimental effect upon the hydrostarter system. Also, the hydrostarter torque for a given pressure remains substantially
the same regardless of the ambient temperature.
The hydrostarter system consists of a reservoir, an engine-driven charging pump, a hand pump, a piston type
accumulator, a starting motor and connecting hoses and fittings.
Hydraulic fluid flows by gravity, or a slight vacuum, from the reservoir to either the engine-driven pump or the hand
pump inlet. Fluid discharging from either pump outlet at high pressure flows into the accumulator and is stored at 3250
psi (22 383 kPa) under the pressure of compressed nitrogen gas. When the starter is engaged with the engine flywheel
ring gear and the control valve is opened, fluid under pressure is forced out of the accumulator, by the expanding
nitrogen gas, and flows into the starting motor which rapidly accelerates the engine to a high. cranking speed. The used
fluid returns directly to the reservoir from the starter.
The engine-driven charging pump runs continuously during engine operation and automatically recharges the
accumulator. When the required pressure is attained in the accumulator, a valve within the pump body opens and the
fluid discharged by the pump is by-passed to the reservoir. The system can be shut down and the pressure in the
accumulator will be maintained.
The precharge pressure of the accumulator is the pressure of the nitrogen gas with which the accumulator is initially
charged. This pressure must be checked before the system pressure is raised for the initial engine start. To check the
precharge pressure, open the relief valve, on the side of the hand pump, approximately 1/2 turn, allowing the pressure
gage to return to zero. Close the relief valve and pump several strokes on the hand pump. The gage should show a
rapid pressure rise from zero to the nitrogen precharge pressure, where it will remain without change for several
additional strokes of the pump.
Fig. 6 - Schematic Diagram of Hydrostarter System Showing Oil Flow