G 20 3/4 Ton Van V8-305 5.0L VIN H 4-bbl (1984)
c. If unable to adjust dwell to specifications, or if reading does not fluctuate, refer to C3 System Section.
9.
Stop engine. Seal mixture screw cavities with RTV sealer and install bleed valve cover.
10.
Reinstall air cleaner and reconnect vacuum hoses, then check curb idle speed.
Fig. 7 Idle air bleed valve adjustment
MIXTURE ADJUSTMENT B
1.
Install gauging tool J-33815-2 or equivalent in ``D'' shaped hole on throttle side of air horn, Fig. 7, with end of tool positioned above open cavity
next to idle air bleed valve.
2.
Hold gauge down lightly to bottom MC solenoid plunger and adjust idle air bleed valve so that tool will pivot over and just contact top of valve.
Remove gauging tool.
3.
Remove plugs covering idle mixture adjusting screws as outlined under ``Concealment Plug Removal'' in the appropriate carburetor section. Turn
mixture screws in (clockwise) until lightly seated, then back screws out 3 turns.
4.
Reinstall carburetor using a new gasket, with air cleaner removed and vacuum hoses disconnected and plugged as outlined on underhood vehicle
emissions label.
5.
Start engine and run until it reaches normal operating temperature and dwell begins to fluctuate.
6.
Place automatic transmission in Drive (manual transmission in Neutral) and adjust mixture screws equally to obtain a fluctuating dwell reading
between 25° and 35° (as close to 30° as possible). Turn mixture screws equally, 1/8 turn per adjustment, allowing time between adjustments for
engine to stabilize. If dwell reading is below 25°, turn screws counterclockwise; if reading is above 35° turn screws clockwise.
7.
If unable to obtain specified dwell reading, refer to C3 System Section.
8.
Stop engine. Seal mixture screw cavities with RTV sealer and install idle air bleed valve cover.
9.
Install air cleaner and reconnect vacuum hoses, then ensure curb idle speed is within specifications.
MIXTURE ADJUSTMENT C
1.
Install gauging tool J-33815-2, BT-8253-B or equivalent in ``D'' shaped hole on throttle side of air horn, with end of tool positioned above open
cavity next to idle air bleed valve.
2.
Hold gauge down lightly to bottom MC solenoid plunger and adjust idle air bleed valve so that tool will pivot over and just contact top of valve.
Remove gauging tool.
3.
Disconnect and plug hose at canister purge valve, start engine and run until it reaches normal operating temperature.
4.
With engine at specified curb idle speed in drive (neutral for manual transmission models), slowly adjust idle air bleed valve to obtain a fluctuating
dwell meter reading within the 25-35° range, as close to 30° as possible. Turn valve 1/8 of a turn at a time, clockwise or counterclockwise as
needed, allowing time between each adjustment for dwell reading to stabilize.
5.
If specified dwell reading cannot be obtained, stop engine and remove plugs covering idle mixture adjusting screws as outlined under
``Concealment Plug Removal'' in the appropriate carburetor section.
6.
Turn each mixture screw in (clockwise) until lightly seated, then back screws out 3 turns.
7.
Reinstall carburetor, leaving air cleaner removed and vacuum hoses disconnected as outlined on underhood emissions label.
8.
Start engine and run until it reaches normal operating temperature, then perform idle air bleed valve adjustment as outlined in step 4.
9.
If specified dwell reading cannot be obtained, proceed as follows:
a. If dwell reading is less than 25°, turn each mixture screw counterclockwise one turn, then repeat step 4.
b. If dwell reading is greater than 35°, turn each mixture screw clockwise one turn, then repeat step 4. If specified dwell reading still cannot be
obtained, check for C3 system malfunction as outlined in ``System Performance Check.''
10. Seal idle mixture adjusting screw cavities with RTV sealer and ensure that idle speed is within specification.
