CIRRUS AIRPLANE MAINTENANCE MANUAL MODEL SR22

ENGINE FUEL SYSTEM

1. GENERAL This chapter describes those units and components which deliver metered fuel and air to the engine. Com- ponents covered include the manifold pressure gage/fuel flow gage. For additional information on system components, refer to the manufacturer’s approved Instructions For Continued Airworthi- ness and/or other service instructions. The fuel injection system is of the multi-nozzle, continuous-flow type which controls fuel flow to match engine air flow. Any change in position, engine speed, or a combination of these, causes fuel flow to change in the correct relation to engine air flow. (See Figure 73-001) Fuel is drawn from the supply tanks by the engine-driven fuel pump, where the fuel is metered based on engine and environmental conditions. Excess fuel is returned to the tank. A boost pump is installed for use in starting and vapor suppression. When liquid fuel leaves the fuel-pump pressure chamber, it is directed to an integral mixture control valve. The mixture control valve shaft is linked to the cockpit mixture control. From the mixture control valve, fuel is directed to the fuel metering valve mounted on the side of the throttle body. The shaft that positions the throttle body butterfly valve also positions the metering valve and is linked to the cockpit throttle control. From the fuel metering valve, fuel passes through the fuel flow meter, then to the fuel manifold valve. The fuel manifold valve contains a diaphragm chamber and the necessary ports which connect to the fuel injector lines. When fuel pressure reaches approximately 3.5 psi, the manifold valve admits fuel to the six ports in the manifold. The spring-loaded diaphragm works with a ported plunger which distributes the pre- cise amount of fuel, via the fuel injector lines, to the fuel injector nozzles.

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2. TROUBLESHOOTING

Trouble Probable Cause Remedy

Engine will not start and no fuel No fuel to engine. Check level. flow indication. Mixture control improperly rigged. Check mixture control for proper rigging. Refer to the manufac- turer’s approved Instructions For Continued Airworthiness and/or other service instructions.

Engine not primed. Auxiliary pump switch to BOOST position.

Selector valve in OFF position. Position selector valve to ON posi- tion.

Engine will not start with fuel flow Engine flooded. Turn off boost pump and ignition indication. switch. Advance throttle to full OPEN, retard mixture to full LEAN, and crank engine to clear cylinders of excess fuel. Repeat starting procedure.

No fuel to engine. Loosen one line at nozzle. If no fuel flow shows on gage, replace fuel metering valve.

Rough idle. Nozzle restricted. Remove nozzles and clean. Refer to the manufacturer’s approved Instructions For Continued Airwor- thiness and/or other service instructions.

Improper idle mixture. Adjust fuel-air mixture. Refer to the manufacturer’s approved Instructions For Continued Airwor- thiness and/or other service instructions.

Poor acceleration. Idle mixture incorrect. Adjust fuel-air mixture. Refer to the manufacturer’s approved Instructions For Continued Airwor- thiness and/or other service instructions.

Unmetered fuel pressure too high. Lower unmetered fuel pressure. Refer to the manufacturer’s approved Instructions For Contin- ued Airworthiness and/or other service instructions.

Worn linkage. Replace worn component of link- age.

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Trouble Probable Cause Remedy

Engine runs rough. Restricted nozzle. Remove and clean all nozzles. Refer to the manufacturer’s approved Instructions For Contin- ued Airworthiness and/or other service instructions.

Improper mixture. Improper pump pressure, replace pump. Refer to the manufacturer’s approved Instructions For Contin- ued Airworthiness and/or other service instructions.

Low fuel flow indication. Restricted flow to metering valve. Check mixture control for full travel.

Inadequate flow from fuel pump. Verify pump pressure, adjust engine-driven pump. Refer to the manufacturer’s approved Instruc- tions For Continued Airworthiness and/or other service instructions.

High fuel flow indication. Restricted flow beyond metering Check for restricted nozzles or valve. fuel metering valve. Clean or replace as required. Refer to the manufacturer’s approved Instruc- tions For Continued Airworthiness and/or other service instructions.

Restricted recirculation passage Replace engine-driven fuel pump. in fuel pump. Refer to the manufacturer’s approved Instructions For Contin- ued Airworthiness and/or other service instructions.

Fluctuating or erroneous fuel flow Vapor in system, excess fuel tem- If not cleared with boost pump, indication. perature. check for clogged ejector jet in vapor separator cover.

Air in fuel flow gage line. Leak at Repair leak and purge line. gage connection.

Poor idle cut off. Fuel flow continues to engine. Check mixture control is in full idle cut off. Check boost pump is OFF. If neither, replace manifold valve.

Fluctuating fuel flow Fuel vapor as a result of high If not cleared with auxiliary indications. ambient temperatures. pump, check for clogged vent in fuel pump vapor separator cover.

Air in fuel flow gage line. Leak at Repair leak and purge line. gage connection.

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Trouble Probable Cause Remedy

Unmetered fuel pressure too Internal orifices plugged. Clean internal orifices injector high. pump. Refer to the manufacturer’s approved Instructions For Contin- ued Airworthiness and/or other service instructions.

Unmetered fuel pressure drop. Relief valve stuck open. Repair or replace fuel pump.

Very high idle and full throttle. Relief valve stuck closed. Repair or replace fuel pump.

Fuel pressure present. Check valve stuck open. Repair or replace fuel pump. No fuel pressure.

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ANNUNCIATOR FUEL FUEL VENT FILLER QUANTITY FILLER VENT INDICATOR

L. WING TANK R. WING TANK

L. WING R. WING COLLECTOR COLLECTOR

SELECTOR FLAPPER VALVE FLAPPER VALVE VALVE DRAIN FIREWALL (5 PLACES)

ELECTRIC FUEL BOOST SELECTOR VALVE AUXILIARY RELAY OPERATION PUMP FUEL PUMP OIL PRIME PRESSURE RETURN SENSOR RIGHT GASCOLATOR (LOW PRESSURE) FEED ENGINE DRIVEN FUEL PUMP MIXTURE CNTL. RETURN LEFT FEED STARTING FUEL CIRCUIT / DAU FLOW Serials 0278 and subs, INDICATOR 0002 thru 0277 after SB 22-73-01.

OFF TO SELECTOR VALVE FUEL BOOST THROTTLE RELAY METERING NOTE VALVE ELECTRIC FUEL PUMP In Prime mode, relay allows AUXILIARY high-speed pump operation until PUMP 10 psi oil pressure is reached then PRIME drops to low-speed operation. TO INJECTOR GASCOLATOR In Prime mode, relay allows MANIFOLD high-speed pump operation until 2-4 psi fuel pressure is Serials 0002 thru 0277 before SB 22-73-01. reached then drops to low-speed operation. FUEL PRESSURE SWITCH Serials 0002 thru 2333, 2335 thru 2419, 2420 thru 2437. SR22_MM28_1350E Figure 73-001 Fuel System Schematic EFFECTIVITY: All 73-00 Page 5 15 Apr 2007 CIRRUS AIRPLANE MAINTENANCE MANUAL MODEL SR22

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