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6C-22
1977 PONTIAC SERVICE M A N U A L
VACUUM
BREAK
IDLE
SOLENOID
\
ELECTRIC
CHOKE
Fig.
6C-36 2GE Carburetor
Fig.
6C-37 2GC Carburetor
body \ocated just above the thrott\e vahe.
An Exhaust Gas Recirculation (E.G.R.) system is used
to meet emission requirements for oxides of nitrogen (NOX).
Vacuum for E.G.R. is supplied through a tube in the float
bowl (location "J"). On 2GC V8 models, a small cup
restriction is located behind the E.G.R. vacuum tube to
slightly delay E.G.R. valve operation in the off-idle range.
The combination vacuum and mechanically operated
power systems, consisting of two power valves, provides
accurate control
of air/fuel
mixtures
for emission
requirements. One power valve is located in the bottom of the
accelerating pump well and the other in the bottom of the
fuel bowl.
ALL MODELS
The float needle seat windows have been removed from
all models for improved fuel vapor handling during hot
engine operation. On California 2GC models, the float valve
is rubber tipped and uses a pull clip for smooth operation of
the valve in the seat. A fuel inlet filter check valve is used
to shut off fuel flow to the carburetor float bowl to prevent
fuel leaks if a vehicle roll-over should occur.
Fuel for the pump system is obtained through a hole
located in a raised cast-in boss on the floor of the float bowl
which prevents the entry of dirt into the accelerator pump
-
power valve fuel inlet passage. The pump plunger head is
designed with an expander spring beneath the pump cup to
maintain good pump wall contact during pump operation.
On 2GE models, except 17057 180-17057 182, the pump
plunger head includes a small by-pass orifice. During heavy
acceleration when the duration spring is compressed, the
tension of the spring is not sufficient to seat the plunger stem
inside the plunger head. When this happens, fuel in the pump
well, beneath the plunger head, is forced through the by-pass
orifice into the plunger head and around the unseated plunger
stem where it passes on up into the float bowl to slightly
reduce pump Fuel dehvery to the venturl area on heavy
acceleration.
C A U T I 0 N : The by-pass type accelerator pump
assembly must not be interchanged with other
models, unless specified; to do so may cause serious
performanace complaints.
The end of the pump plunger stem is upset in
manufacturing to provide the "clipless" retaining feature.
The pump plunger assembly may be removed from the inner
lever by twisting upset end with small pliers until it breaks.
The service pump assembly has a grooved end and is provided
with a retaining clip.
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