Page Number - 26
Form 824262
Results
Scenario
Idle
Pressure
Idle Flow
Peak Pressure
(CLOSED)
Peak Flow
(BYPASS)
Potential Causes
1
Normal
Normal
Greater than
maximum fuel
volume require-
ment*
Normal
50% to 100%
higher than
spec
Normal
2.5 to 4.0 LPM
(.7 to 1.0 GPM)
Fuel system is
operating normally
2
Normal to
slightly low
Low
Less than maxi-
mum fuel volume
requirement*
Normal
50% to 100%
higher than
spec
Low
Less than
2.5 LPM
(.7 GPM)
Blocked fuel filter, inlet
strainer or pinched
supply line
3
Low
High
Greater than
2.5 LPM
(.7 GPM)
Normal
50% to 100%
higher than
spec
Normal
2.5 to 4.0 LPM
(.7 to 1.0 GPM)
Faulty pressure
regulator
(low pressure)
4
High
Low
Less than maxi-
mum fuel volume
requirement*
Normal
50% to 100%
higher than
spec
Normal
2.5 to 4.0 LPM
(.7 to 1.0 GPM)
Faulty pressure
regulator
(high pressure)
5
Low
Low
Less than maxi-
mum fuel volume
requirement*
Low
Less than
50% higher
than spec
Low
Less than
2.5 LPM
(.7 GPM)
Failing fuel pump or
insufficient power
supply
*See Appendix A for maximum engine fuel volume requirement
Inlet strainer/sock
Fuel return line
Pressure Regulator
Fuel Rail
Fuel Filter
Fuel Pump
Fuel Supply Line
To manifold vacuum
or atmosphere
Appendix B – Return Fuel System Diagnostic Guide
