Main Metering System; Accelerating System; Electric Choke L4-151 Engine; Secondary Power Enrichment System - Pontiac TRANS AM 1977 Service Manual

FUEL SYSTEM 6C-9
P R I M A R Y I D L E A I R B L E E D
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n
P R I M A R Y I D L E TUBE
mi'qg
I i
I D L E
TRANS
P R I M A R Y
SECONDARY
I
Fig.
6C-10
Idle System
Main Well
Air B M
Main Momring Jet
Main Well Tuba 2945
Fig.
6C-1 1
Main Metering System
PUMP DIAPHRAGM ASM
Fig.
6C-12
Accelerating System
ELECTRIC CHOKE L4-151 ENGINE (FIG.
6C-17)
A ceramic resistor in the electric choke assembly is
heated by electric current and the resistor warms the
thermostatic coil for precise timing of choke valve opening
for good engine warm-up performance.
The electric choke operates as follows:
Power Valve
Dirnh.am
Fig.
6C-13
Primary Power Enrichment System
U v U 2948
Fig.
6C-14
Secondary Power Enrichment System
The electric choke receives electric current operating
through the engine oil pressure switch whenever the engine
is running. The electric current flows to a ceramic resistor
that is divided into two separate sections
-
a small center
section for gradual heating of the thermostatic coil, .and a
large outer section for additional rapid heating of the
thermostatic coil.
The ceramic resistor functions as follows:
AIR TEMPERATURE BELOW 50°F., (10°C.)
Electric current, applied to the small section of the
ceramic resistor causes the section to heat up and warm the
thermostatic coil which allows gradual opening of the choke
valve for good cold engine warm-up performance. As the
small section of the ceramic resistor continues to produce
heat, a temperature-sensitive bimetal disk causes a spring
loaded contact to close also applying electric current to the
large section of the ceramic resistor causing the large section
to heat up. Heat from the larger section of the ceramic resistor
increases the rate of heat flow to the thermostatic coil for
more rapid opening of the choke valve.
AIR TEMPERATURE 70°F.
(21°C.)
A N D ABOVE
Electric current is applied directly to both the small
section and through the spring contact to the large section
of the ceramic resistor to provide a rapid heating of the