GMC C Series 1993, Руководство по ремонту

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6C1-4 MODEL 295 TBI UNIT
GENERAL DESCRIPTION
The fuel control system has an electric fuel pump
located in the fuel tank with the gage sending unit. The
pump delivers fuel to the throttle body injection (TBI)
unit through the fuel supply line, then through an in-line
fuel filter. The pump is designed to provide pressurized
fuel above 220 kPa (32p si). Vehicles with two fuel
tanks have an electric fuel pump and gage sending unit
in eiach fuel tank.
A pressure regulator in the TBI unit keeps fuel avail­
able to the injectors at a constant pressure between
179 and 220 kPa (26 and 32 psi). Fuel in excess of the
injector’s requirement returns to the fuel tank by a sepa­
rate line.
The engine control module (ECM) monitors informa­
tion from several sensors to determine fuel require­
ments based on engine operating conditions. The fuel
is delivered under one of several conditions called
“modes.” All modes are controlled by the ECM.
The DC governor motor is electronically actuated and
controlled ! by the ECM through the governor control
module (governor motor driver circuit). Governed opera­
tion prevents excessive engine speed under light loads,
yet allows complete throttle opening for full power under
heavy loads. ;
TBI unit Model 295 consists of these major assem-
blies: , •
• Fuel meter body assembly-with':.
— TBI fuel injectors
— Pressure regulator
• Throttle body assembly, with:
; — Throttle Position Sensor (TP Sensor)
— Idle Air Control (IAC) valve
( I G o v e r n o r motor and throttle drive assembly
| Vacuum ports
THROTTLE BODY DISASSEMBLY
IDLE AIR CONTROL (IAC) VALVE
N O T IC E : T h e IA C v a lv e is a n e le c tr ic a l c o m ­
p o n e n t a n d m u s t n o t b e s o a k e d in a n y liq u id
c le a n e r o r s o lv e n t a s d a m a g e m a y r e s u lt
Remove or Disconnect (Figures 2 and 3)
1. IAC valve.
• Remove IAC valve screw assemblies.
2. Fuel meter body cover.
I ? Inspect
• Fuel meter body cover and seal for damage.
Replace cover if seal is damaged. Do not try to
remove the,seal from the fuel meter body cover.
FUEL INJECTORS
Each fuel injector is serviced as a complete assembly
only (figure 5).
2. IAC valve O-ring arid discard.
THROTTLE POSITION SENSOR
(TP SENSOR)
N O T IC E : T h e T P s e n s o r is a n e le c tric a l c o m ­
p o n e n t a n d m u s t n o t b e s o a k e d in a n y liq u id
c le a n e r o r s o lv e n t a s d a m a g e m a y re s u lt.
N O T IC E : U s e c a re in re m o v in g th e fu e l in je c ­
to rs to p r e v e n t d a m a g e to th e e le c tr ic a l c o n ­
n e c t o r t e r m in a ls , i n je c t o r f ilt e r , a n d f u e l
n o z z le . T h e f u e l in je c to r is s e r v ic e d a s a
c o m p le t e a s s e m b ly o n ly . A ls o , s in c e th e
in je c to r s a r e e le c t r ic a l c o m p o n e n ts , th e y
s h o u ld n o t b e im m e rs e d in a n y ty p e o f liq u id
s o lv e n t o r c le a n e r a s d a m a g e m a y o c c u r.
Important
On the Model 295 TBI Unit, the TP sensor is non-ad-
justable. If replacement is required, be sure to order the
correct one for your engine with the identical part nurm
ber.
Remove or Disconnect (Figures 2 and 3)
1. Two TP sensor attaching screw assemblies.
2. TP sensor from throttle body assembly.
FUEL METER COVER
♦ 4
R e m o v e o r D i s c o n n e c t ( F i g u r e s 2 a n d 3 )
1. Four cover attaching screw assemblies.
Remove or Disconnect (Figures 4 and 5)
i t . . - -
• With fuel meter cover gasket in place to prevent
dartiage to casting, use a screwdriver and fulcrum
to carefully lift out each injector (figure 4).
1. Lower (small) O-ring from nozzle of injectors and
disjcardL
2. Fuel.jmeter cover gasket and discard.
3. Upper! (large) O-ring from top of fuel injector cavity
and discard.
je
• Fuejilinjector filter for evidence of dirt and contami­
nation. If present, check for presence of dirt in fuel
liries arid fuel tank. Clean or replace injector as
neccesary.
inspect