DSG-423 FUEL SYSTEM
04-13
Diagnostic Aids
Fuel Lock Solenoid
:The fuel lock is an electronic solenoid that is opened to allow fuel flow when the key is turned
ON. High temperatures may cause the solenoid to become intermittent, not opening to supply sufficient fuel
pressure.
Fuel Filter
:There is a filter element located in the inlet of the fuel lock which may become clogged and limit fuel flow,
especially at low tank pressures. Check the filter and replace or clean as necessary.
Fuel Line Restrictions
:The vehicle specifications table specifies the fuel line to be a certain size. If the fuel line from
the tank to the fuel lock is not the proper size, or any valves or fittings with flow restrictive characteristics are used,
the fuel flow will not be sufficient to the converter with low tank pressure. Correct any fuel line or fitting restrictions.
Mixer Assembly (Carburetor):It is possible that a backfire may have caused the fuel valve to partially come off of it's
retainer and restrict fuel, check the mixer fuel valves, see section 475-1 for disassembly.
Regulator Assembly (Converter
): If no other problems have been identified, replace the fuel management assembly
with a known good part of the same pressure range. Retest.
7 Check FCV vacuum fitting bypass port. Yes
No
Clean out bypass with a .050 size pin
or drill bit and retest.
CAUTION: Do not enlarge the by-
pass port
Go to Step 8.
• The bypass port is located on the back of the 90 degree
elbow which connects the vacuum line from the converter
to the FCV valve.
Is this bypass closed with dirt or debris?
8 Check for stuck primer button. Yes
No
Try and free the primer button. If you
cannot reseat the primer then see
section 475R-1 for servicing the
converter.
Go to Step 9.
• Key Off.
• Press the primer button on the converter once to assure
the primer is not sticking open. A small amount of fuel that
is trapped between the fuel lock and the converter should
pass through to the carburetor.
Is the primer button stuck in the depressed position?
6 Check regulator operation. Yes
No
The Regulator is malfunctioning. See
section 475R-1 for service of the
converter.
Go to Step 7.
• Using Woodward WTK-1 test kit, install the secondary
pressure gauge as described in section G-1. (note: the
secondary spring color and pressure range)
• Crank the engine
Is the pressure less than "X" psi?
7 Check carburetor air valve for binding. Yes
No
Refer to section 475-1 for servicing the
carburetor.
Go to Step 8.
• With the air cleaner removed, pull the air valve piston
upwards to ensure free movement of the carburetor air
valve.
Is the air valve binding?
8 Check air valve operation. Yes
No
Replace the carburetor and retest.
Refer to Diagnostic Aids below.
• Using the WTK-1 test kit, connect the vacuum gauge
between the carburetor and the FCV valve to measure the
carburetor air valve vacuum (AVV).
• Crank the engine and observe the amount of measured
vacuum.
Is the measured vacuum outside the specifications?
Engine Cranking But Will Not Start (Continued)
Test Step Result Action to Take
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