Mityvac MV5545 - Appendix B

Page Number - 36
Results
Scenario
Idle
Pressure
Idle Flow Peak Pressure Peak Flow Potential Causes
1 Normal Normal
Greater than
maximum fuel
volume require-
ment*
Normal
50% to
100% higher
than spec
Normal
.7 to 1.0 GPM
(2.5 to 4.0 LPM)
Fuel system is operat-
ing normally
2
Normal to
slightly low
Low
Less than maxi-
mum fuel vol-
ume require-
ment*
Normal
50% to
100% higher
than spec
Low
Less than .7
GPM (2.5 LPM)
Blocked fuel filter, inlet
strainer or pinched
supply line
3 Low High
Greater than .7
GPM (2.5 LPM)
Normal
50% to
100% higher
than spec
Normal
.7 to 1.0 GPM
(2.5 to 4.0 LPM)
Under-restricting
pressure regulator
4 High Low
Less than maxi-
mum fuel vol-
ume require-
ment*
Normal
50% to
100% higher
than spec
Normal
.7 to 1.0 GPM
(2.5 to 4.0 LPM)
Over-restricting pres-
sure regulator
5 Low Low
Less than maxi-
mum fuel vol-
ume require-
ment*
Low
Less than
50% higher
than spec
Low
Less than .7
GPM (2.5 LPM)
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