Pontiac Fiero 1988 Service Manual page 378

FUEL SYSTEM 6C-7
consumed. Engage starter again for 3.0
seconds to assure relief of any remaining
pressure.
. » With ignition "OFF", replace "Fuel Pump"
fuse.
1. Remove air cleaner and plug thermal vacuum
port on throttle body unit.
2. Remove steel fuel pipe between throttle body unit
and fuel filter. Use backup wrench to hold fuel
nut on throttle body and fuel filter when
removing fuel line.
3. Install fuel pressure gage between throttle body
and fuel filter. A 9-15 psi gage, such as J-29658,
should be used.
4. Start car and observe fuel pressure reading. It
should be 9-13 psi; if not, refer to EFI Diagnosis
Chart A-5.
5. Remove fuel pressure gage (system must first be
depressurized).
6. Reinstall steel fuel line from filter to throttle body
and torque to 26-34 N-m (19-25 lb. ft).
7. Start car and observe for fuel leaks.
8. Remove plug covering thermal vacuum port on
throttle body and install air cleaner.
FUEL PUMP FLOW TEST - 2.5L TBI ENGINE
(LR8)
1. Test fuel pump by connecting hose from the fuel
filter fuel feed line to a suitable unbreakable
container.
a.
EFI Electric Fuel Pump.
Apply battery
voltage to the fuel pump test terminal
(terminal "G" of ALCL).
2. Fuel pump should supply 1/2 pint or more in 15
seconds.
3. If flow is below minimum, check for fuel
restriction. If there is no restriction, check pump
vacuum and/or pressure.
FUEL SYSTEM PRESSURE TEST - 2.8L-MPFI
ENGINE (L44)
Fuel system diagnosis on this engine is in Section
6E3.
FUEL TANK AND LINES
Inspect the fuel tank, cap and lines for road
damage, which could cause leakage. Inspect fuel cap
for correct sealing and indications 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 dry chemical (Class B) fire
extinguisher handy, (4) wear safety glasses and (5)
siphon or pump fuel into an explosion proof container.
CANISTER PURGE VALVE TEST
1. Remove purge valve control vacuum line at
canister and check for vacuum with engine
operating above idle speed (above 1500 RPM). If
no vacuum is present, perform EGR system
functional test (Section 6E).
2. Apply external vacuum source (such as
hand-operated vacuum/pressure pump J-23738
in combination with manometer J-23951) to the
purge valve control diaphragm. A good valve will
hold vacuum.
3. If the valve will not hold vacuum, replace
canister.
4. If the valve holds vacuum, remove purge line and
check for vacuum with engine operating. If no
vacuum is present, check PCV hoses and PCV
system (Section 6E). Repair or replace as
necessary.
FUEL TANK PRESSURE CONTROL VALVE
1. Disconnect vapor return hose at canister end.
Remove fuel filler cap from tank.
2. Apply a low pressure flow through vapor return
hose. A restricted flow rate should be detected.
3. Disconnect vacuum control hose at valve end.
Connect hand vacuum pump to valve port and
apply 3 inches of mercury. Observe vacuum
reading for 20 seconds. If vacuum drops more
than 1 inch, replace valve.
4. With vacuum applied again, apply a low pressure
flow through vapor return line. An unrestricted
flow rate should be detected. If flow rate is
restricted with vacuum applied, check for
blockage in vapor return line to fuel tank. If no
difference in flow rate can be detected with or
without vacuum applied, replace valve.
5. Reconnect vacuum hoses (refer to Vehicle
Emission Label) and re-install fuel filler cap.
PRESSURE CHECKING EEC SYSTEM
1_ Engine must be cold and at room temperature.
2. Remove tank line at canister and observe for
liquid in the line. Connect a regulated low
pressure source (such as Tool J-23699) to the tank
vapor line.
3. Apply 15 in. Hg pressure to the fuel vapor line.
a. Observe for excessive loss of pressure (more
than 3 inches in five minutes).
b. If negligible pressure loss occurs, check for
fuel vapor smell or fuel loss at points listed
in Diagnostics under Possible Cause.
c. Remove fuel filler cap and check for
pressure in tank.
4. Remove fuel cap and check vent line for
obstructions.
Any loss of fuel or vapor from the fuel filler cap
would indicate one or more of the following:
• An unsatisfactory seal between the cap and filler
neck.
• A malfunction of filler cap release valve.
EVAPORATIVE SYSTEM PRESSURE TEST
1. Stabilize vehicle at normal operating
temperature.
2. Remove tank vapor line at canister and check for
liquid in the line. Connect hand-operated