Boost Pump Switch - Cirrus SR22 Pilot Operating Handbook

Cirrus Design Section 7
SR22 Airplane Description

Boost Pump Switch

Boost pump operation and engine prime is controlled through the Fuel
Pump BOOST-PRIME switch located adjacent to the fuel selector
valve. The PRIME position is momentary and the BOOST position is
selectable. A two-speed prime allows the fuel pressure to rapidly
achieve proper starting pressure.
Serials 0002 through 0277 before SB 22-73-01: For engine starting,
pressing PRIME causes the boost pump to operate at high speed until
the fuel pressure reaches 2-4 psi. When the fuel pressure reaches the
2-4 psi range, a pressure switch in the fuel injection line switches the
boost pump to the low-speed mode to provide a 4-6 psi fuel pressure
boost. Selecting BOOST energizes the boost pump in low-speed
mode to deliver a continuous 4-6 psi boost to the fuel flow for vapor
suppression in a hot fuel condition.
Serials 0278 and subs, and serials 0002 through 0277 after SB 22-73-
01: An oil pressure based system is used to control boost pump
operation. The oil pressure/oil temperature sensor provides a signal to
the starting circuit/DAU to generate a ground for the oil annunciator
and the fuel system. This system allows the fuel pump to run at high
speed (PRIME) when the engine oil pressure is less than 10 PSI.
Whenever the engine oil pressure exceeds 10 PSI, pressing PRIME
will have no effect. Selecting BOOST energizes the boost pump in low-
speed mode regardless of oil pressure to deliver a continuous 4-6 psi
boost to the fuel flow for vapor suppression in a hot fuel condition.
The boost pump operates on 28 VDC supplied through the 5-amp
FUEL PUMP circuit breaker on Main Bus 2.
P/N 13772-001 7-61
Revision A5