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TM 10-4320-342-24
Section III. PRINCIPLES OF OPERATION
1-14. INTRODUCTION.
Although there are minor differences between the 200 GPM Pump and the 600 GPM Pump (all are confined to the
200/600 GPM fuel pumps) both pump assemblies operate in essentially the same manner.
1-15. PRINCIPLES OF OPERATION.
a.
Priming Fuel and Fuel System. Refer to Figures 1-2 and 1-3.
(1)
The engine-driven centrifugal pump utilizes an inducer and impeller. Fuel enters the pump through a
screen and is discharged through a manually operated ball valve and out the discharge elbow. Pump
incorporates an electromechanical clutch to allow engine to be started under no load conditions.
(2)
Priming of pump is semiautomatic and is initiated when engine is operating, pump pressure switch is closed
(indicating no discharge pressure), clutch engage switch is on and manually operated primer shut-off and
ball-valves are open (turn on procedure). When these conditions are satisfied, the ejector solenoid and
drain solenoid valves open and allow bleed air from the engine to flow through the compressor discharge
solenoid valve, the check valve and the ejector to the fuel drain tank.
(3)
The suction created by the ejector orifice evacuates a mixture of air and fuel vapor from the pump at the
discharge elbow. The fuel and air mixture is discharged into the drain tank, where the air is vented thru the
top opening while fuel is trapped in the tank.
(4)
When sufficient vacuum exists in the pump and attached inlet and outlet hoses, fuel in suction line rises
above level of impeller. When this occurs, pump is primed and begins to pump fuel.
(5)
After the pump is primed, the priming system is deactivated by the pump discharge pressure switch, which
causes the compressor discharge solenoid and the drain solenoid valves to close when pump discharge
pressure reaches approximately 20 psi.
(6)
When pump is primed and operating, the manually operated prime shutoff valve is closed and the tank
suction valve is briefly opened to allow draining of drain tank by feeding it to the pump inlet.
b.
Engine.
(1)
The engine is essentially a self contained power unit requiring only fuel, ambient air and electrical power for
operation.
1-11
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