DSG-423 FUEL SYSTEM
04-20
The pinpoint tests below should be performed after the preliminary tests and “Engine Cranks but Will Not Start”
chart Steps 1-3. Any electrical diagnostics should have been performed to eliminate any sensor, GCP or solenoid
valve problems before proceeding.
Engine Misses
Test Step Result Action to Take
1 Check regulator fuel supply. Yes
No
The fuel filter may be restricting flow or
the fuel lock may be intermittent. Go
to Step 2.
Go to Step 3.
• Using Woodward WTK-1 test kit, install the primary
pressure gauge as described in section 475G-1.
• With the Engine at Idle or on acceleration, to induce
symptom
Is the primary pressure less than "X" psi or fluctuating?
2 Check fuelock supply voltage. Yes
No
12 volt fuelock activation circuit is
open, shorted to ground or the GCP
module is faulty. Check wiring,
connectors and fuses for possible
cause.
Fuel filter element may be clogged,
inspect and/or replace the fuel filter as
described in section 475F-1. Repeat
test step 1, if pressure is still less than
specified replace the fuel lock and re-
test before moving to Step 3.
• Key OFF.
• Disconnect Fuelock connector from harness.
• Key ON.
• Using a high impedance DVOM, check for 12 volt supply
at the harness connector.
Is the voltage less than 11.5 volts?
3 Check regulator operation. Yes
No
Remove the vacuum hose from the
FCV valve to the regulator. If the
pressure is not -1.5 inches of w.c.,
the Regulator is malfunctioning. See
Section 475R-1 for service of the
regulator.
Go to Step 4.
• Using Woodward WTK-1 test kit, install the primary and
secondary pressure gauge as described in section 475G-
1. (note: the secondary spring color and pressure range)
• At Idle or accelerate to induce symptom.
Are the pressures less than "X" specified?
4 Check FCV operation. Yes
No
This would indicate the engine is
experiencing a momentary mixture
change. Possible causes:
• Faulty FCV valve connection or
vacuum leaks, go to Step 5.
• GCP fault.
Go to Step 6.
• At Idle or accelerate Engine to induce symptom.
• Disconnect the vacuum hose from the FCV valve to the
regulator
Does the engine continue to miss with the hose
disconnected?
5 Check FCV supply voltage. Yes
No
12 volt FCV circuit is open, shorted to
ground or the GCP module is faulty.
Check wiring, connectors and fuses
for possible cause..
Refer to section 475-1 for servicing the
carburetor. Also refer to the Diagnostic
Aids below.
• Key OFF.
• Disconnect FCV connector from harness.
• With engine at idle and upon acceleration.
• Using a high impedance DVOM, check for 12 volt supply
at the harness connector.
Is the voltage less than 11.5 volts?
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