Firebird V8-305 5.0L (1982)
Choke Pull-off: All Technical Service Bulletins
Engine - Hard Start/Poor Warm Up Performance
Number 84-6(Gasoline)-53A Date 4/85
Subject:
CARBURETOR VACUUM BREAK TESTING PROCEDURE
ALL CARBURETORS EQUIPPED WITH VACUUM BREAKS
"Please discard previous bulletin 84-6 (Gasoline)-53 (dated 7/01/84) due to this revision."
Hard starting or poor warm-up performance on a carbureted engine may be due to a leaking vacuum break unit. The vacuum break, sometimes called the
"choke pull-off", opens the carburetor choke valve against the tension of the thermostatic choke coil during cold engine start-up. A vacuum break unit
with a leaking diaphragm will not open the choke valve to the proper position, and may cause a cold engine to load up with fuel, resulting in black
exhaust smoke.
FIGURE 1 - PLUGGING AIR BLEED HOLES
VACUUM BREAK TESTING PROCEDURE:
1.
Determine whether the vacuum break has a bleed orifice. If it does, it should be plugged as shown. See Figure 1 for possible locations.
^
Most rear or secondary side units have a bleed.
^
Most front or primary side units do not.
FIGURE 2 - VACUUM BREAK TESTING PROCEDURE
