G420E/G424E Tier LP Engine Test And Adjustments 81
N-CA55-500TR Service AVV
(Air Valve Vacuum) Testing
AVV Test Hardware
1. Mixer AVV test fitting ¼” NPT X ¼” hose barb.
2. Union Tee ¼” NPT with three ¼” NPT X ¼” hose
barb.
3. Vacuum hose.
4. 0-20 in W.C. Magnehelic Gauge (inches of water
column).
AVV Test
1. Install the Union Tee fitting between the FTV and
the AVV fitting.
2. Connect the vacuum hose from the Union Tee
fitting to the Magnahelic gauge (Figure T1). You
should now have the gauge inline between the
FTV and the mixer to throttle adapter.
3. With the engine running at idle (700 RPM) the
AVV should be between 5" and 10" water column.
NOTE
If the measured water column is
excessively high, check for a sticking or
binding piston diaphragm assembly
inside the mixer. (See Chapter 8 for
removal, installation and disassembly of
the N-CA55-500TR mixer).
WARNING
DO NOT spray carburetor cleaner or
solvent into the mixer while installed on
the engine. These chemicals may damage
the oxygen sensor and cause pre-mature
failure of the catalytic muffler.
Figure T1
Gauge
Fitting
AVV Fitting
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