B737-700/800/900 Fuel System
Engine Fuel System
Fuel is delivered under pressure from fuel pumps located in the fuel tanks. The fuel flows
through a fuel spar shutoff valve located at the engine mounting wing stations. The fuel passes
through the first stage engine fuel pump where pressure is increased. It then passes through two
fuel/oil heat exchangers where IDG oil and main engine oil heat the fuel. A fuel filter then
removes contaminants. Fuel automatically bypasses the filter if the filter becomes saturated.
Before the fuel bypass occurs, the fuel FILTER BYPASS alert illuminates on the fuel control
panel.
The second stage engine fuel pump adds more pressure before the fuel reaches the hydro
mechanical unit (HMU). To meet thrust requirements, the EEC meters fuel through the HMU.
The spar fuel shutoff valve and engine fuel shutoff valve allow fuel flow to the engine when both
valves are open. The valves are open when the engine fire warning switch is in and the start
lever is in IDLE. Both valves close when either the start lever is in CUTOFF or the engine fire
warning switch is out. SPAR VALVE CLOSED and ENG VALVE CLOSED lights located on the
overhead panel indicate valve position.
Fuel flow is measured after passing through the engine fuel shutoff valve and is displayed on the
display unit. Fuel flow information is also provided to the FMS.
Fuel is delivered under pressure from fuel pumps located in the fuel tanks. The fuel flows
through a fuel spar shutoff valve located at the engine mounting wing stations. The fuel passes
through the first stage engine fuel pump where pressure is increased. It then passes through two
fuel/oil heat exchangers where IDG oil and main engine oil heat the fuel. A fuel filter then
removes contaminants. Fuel automatically bypasses the filter if the filter becomes saturated.
Before the fuel bypass occurs, the fuel FILTER BYPASS alert illuminates on the fuel control
panel.
The second stage engine fuel pump adds more pressure before the fuel reaches the hydro
mechanical unit (HMU). To meet thrust requirements, the EEC meters fuel through the HMU.
The spar fuel shutoff valve and engine fuel shutoff valve allow fuel flow to the engine when both
valves are open. The valves are open when the engine fire warning switch is in and the start
lever is in IDLE. Both valves close when either the start lever is in CUTOFF or the engine fire
warning switch is out. SPAR VALVE CLOSED and ENG VALVE CLOSED lights located on the
overhead panel indicate valve position.
Fuel flow is measured after passing through the engine fuel shutoff valve and is displayed on the
display unit. Fuel flow information is also provided to the FMS.
Fuel System SGR
IDG Oil Cooler
To Oil Tank
Engine Oil Cooler
From Engine Oil
Scavenge System
Scavenge System
Comparator
