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P/N: 307271
4.12 CONTROLS-OPERATION AND ADJUSTMENTS
The compressor system is designed to match air supply and engine performance with the demand. The
components of the control system are, the blowdown valve, start-run solenoid, compressor inlet valve,
pressure regulator and an engine air cylinder.
The start-run valve that is open in the start run position. This allows air to by-pass the pressure regulator
and go directly to the compressor inlet valve, closing it and to the engine air cylinder, holding the throttle
at idle. When switched to the run position, shutting off the by-pass air. Control air now has to go through
the pressure regulator.
The pressure regulator is referred to as a positive type and its operation is proportional to system pressure.
As pressure increases it opens, allowing air to pressurize the inlet valve and air cylinder. When there is an
air demand, the pressure decreases and the regulator starts to close, relieving the pressure in the inlet valve
and air cylinder. An orifice in the regulator bleeds the air out of control line between regulator, engine air
cylinder and inlet valve supplies a signal proportional to the system pressure the inlet valve will modulate.
With no air demand the pressure rises, the signal air from the regulator closes the inlet valve. When an air
demand is present or the pressure falls, the air signal is removed allowing the inlet valve to open to match
air demand.
The blowdown valve has two functions in the system. First it prevents excessive pressure in the start and
unload modes by bleeding off the small amount of air being drawn in during idle. Secondly it relieves or
blows down the system on shutdown. This valve is not adjustable.
ADJUSTMENT
When performing control adjustments care must be taken in regard to safety as the compressor must be
running. Be aware of moving parts, as well as, hot items, such as fans, belts and exhaust components.
IDLE OR UNLOAD SPEED ADJUSTMENT (For 100 PSI System)
With the compressor warmed up and all service valves closed, move start-run switch to run position. Air
pressure will build to 120 psig. If air pressure is less than 120 psig, adjust regulator up by turning the
adjusting screw clockwise. If air pressure is greater than 120 psig, adjust regulator down by turning the
adjusting screw counter-clockwise. Check engine speed with a photo tachometer.
If idle speed is not as listed in specifications, adjustment will be required.
Note: If your unit is rated at a higher pressure add 20psi to the working pressure for unload pressure; ex:
150 PSI working = 170 unload.
IDLE SPEED ADJUSTMENT PROCEDURES
On the injection pump throttle arm, there are two adjusting screws. The air cylinder connected to the
throttle arm, this air cylinder moves throttle to increase and decrease engine speed with air demand. When
adjusting idle speed, the air cylinder should be fully extended moving throttle arm towards front of engine.
To adjust idle speed, loosen locknut on adjusting screw towards rear of engine. Turning adjustment screw
clockwise will increase speed. If proper speed cannot be obtained with the adjustment screws, it may
require loosing the locknut on air cylinder shaft and adjusting clevis. By turning clevis onto shaft speed
will increase, by turning clevis out, speed will decrease. After proper speed is set, tighten all locknuts.