G643(E) Service Manual Chapter 2. Recommended Maintenance 28
Pressure Regulator/Converter
Inspection
• Visually inspect the pressure regulator/converter
(B) housing for coolant leaks.
• Refer to Chapter 6 if the pressure
regulator/converter requires replacement.
Fuel Trim Valve Inspection (FTV)
• Visually inspect the fuel trim valves (C) for
abrasions or cracking. Replace as necessary.
• To ensure a valve is not leaking a blow-by test can
be performed.
1. With the engine off, disconnect the electrical
connector to the FTVs.
2. Disconnect the vacuum line from the FTVs to the
pressure regulator/converter at the converter’s
tee connection.
3. Lightly blow through the vacuum line connected to
the FTVs.
Air should not pass through the FTVs when de-
energized.
If air leaks past the FTVs when de-energized,
replace the FTVs.
Inspect Air/Fuel Valve Mixer Assembly
• Refer to Chapter 6 for procedures regarding the
LP mixer (D).
Inspect for Intake Leaks
• Visually inspect the intake throttle assembly (E),
and intake manifold for looseness and leaks.
Repair as necessary.
Inspect Throttle Assembly
• Visually inspect the throttle assembly motor
housing for coking, cracks, and missing cover-
retaining clips. Repair and/or replace as
necessary.
NOTE: Refer to Chapter 6 for procedures on
removing the mixer and inspecting the throttle plate.
Checking the TMAP Sensor(G643E only)
• Verify that the TMAP sensor (F) is mounted tightly
into the manifold or manifold adapter (E), with no
leakage.
• If the TMAP is found to be loose, remove the
TMAP retaining screw and the TMAP sensor from
the manifold adapter.
• Visually inspect the TMAP O-ring seal for damage.
Replace as necessary.
• Apply a thin coat of an approved silicon lubricant
to the TMAP O-ring seal.
• Re-install the TMAP sensor into the manifold or
manifold adapter and securely tighten the
retaining screw.
Exhaust System Maintenance
Inspect Engine for Exhaust Leaks
• Start the engine and allow it to reach operating
temperatures.
• Perform visual inspection of exhaust system from
the engine all the way to the tailpipe. Any leaks,
even after the post-catalyst oxygen sensor, can
cause the sensor output to be effected (due to
exhaust pulsation entraining air upstream).
Repair any/all leaks found. Ensure the length
from the post-catalyst sensor to tailpipe is the
same as original factory.
• Ensure that wire routing for the oxygen sensors is
still keeping wires away from the exhaust system.
Visually inspect the oxygen sensors to detect any
damage.(G643E only)
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