Pontiac Fiero 1988 Service Manual page 377

6C-6 FUEL SYSTEM
Fig 7 Accelerator Pedal Assembly
• A fuel tank overfill protector is provided to assure
adequate room for expansion of liquid fuel
volume with temperature changes.
• At one point fuel tank venting system is provided
on all series to assure that the tank will be vented
under any normal car attitude. This is
accomplished by using a dome type fuel tank.
• To protect the tank from mechanical damage in
the event of excessive internal or external
pressures resulting from the operation of this
closed system, a pressure-vacuum relief valve,
located in the fuel cap, will control the tank
internal pressure.
C A N I S T E R P U R G E
VALVE
A N D S O L E N O I D
The Electronic Control Module (ECM) controls
the vacuum to the canister purge valve by using an
electrically operated solenoid valve. When the
computer command control system is in "Open Loop",
the solenoid valve is energized and blocks vacuum to
the canister purge valve. When the system is in "Closed
Loop", the solenoid vavle is de-energized and vacuum
is supplied to operate the purge valve. This releases the
fuel vapors, collected in the canister, into the induction
system. (See Section 6E Emission Control System).
If the Canister Purge Valve is faulty, the canister
assembly must be replaced.
FUEL
T A N K
PRESSURE CONTROL VALVE
A Fuel Tank Pressure Control Valve is used with
the vapor canister in the line to fuel tank. Its purpose
is to control the rate of fuel vaporization from the tank
when the engine is not running and to act as a tank vent
when engine is running.
The diaphragm operating pressure difference is
small (3-4 PSI) so PCV vacuum can move the valve.
Fuel tank pressure can build on a warm day, so it will
act on the lower side of the diaphragm and open the
valve when pressure rises high enough. The higher
pressure on the tank slows the evaporation of the fuel
while allowing some vapor (through orifice) to the
canister. (See Section 6E Emission Control System.)
DIAGNOSIS
All diagnosis related to the fuel system not found
in the diagnosis section can be found in the Engine
Performance Diagnosis located at the beginning of
Section 6. Also see Section 6E for Emission
Component Diagnosis (EECS, EGR, PCU and EFE).
C A U T I O N : T o r e d u c e t h e
risk
o f f i r e
a n d p e r s o n a l i n j u r y , it i s n e c e s s a r y t o
r e l i e v e t h e f u e l s y s t e m p r e s s u r e
b e f o r e s e r v i c i n g f u e l s y s t e m
c o m p o n e n t s .
When repair to the system has been completed,
start the engine and check all connections that were
loosened for possible leaks.
INSPECTION OF FUEL SYSTEM
Make certain that there is fuel in the tank.
The fuel tank, cap and lines should be inspected
for road damage, which could cause leakage. Inspect
fuel cap for correct sealing or indication of physical
damage. Replace any damaged or malfunctioning
parts.
Before attempting service of any type on the fuel
tank, always (1) Remove negative battery cable from
battery, (2) place "no smoking" signs near work area,
(3) be sure to have C02 fire extinguisher handy, (4)
wear safety glasses and (5) siphon or pump fuel into an
explosion proof container.
FUEL SYSTEM PRESSURE TEST - 2.5LTBI
ENGINE (LR8)
This test must be performed when diagnosing the
fuel system.
C A U T I O N : T o r e d u c e t h e r i s k o f f i r e
a n d p e r s o n a l i n j u r y , it i s n e c e s s a r y t o
r e l i e v e t h e f u e l s y s t e m p r e s s u r e
b e f o r e s e r v i c i n g f u e l s y s t e m
c o m p o n e n t s . T o d o t h i s :
• Remove "Fuel Pump" fuse from fuse block
in passenger compartment.
• Crank engine - engine will start and run
until fuel sunnlv
r p m a m - - * -
n