1988 PONTIAC FIERO Service Repair Manual

6E2-A-114 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
CHART A-3
(Page I of 2)
ENGINE CRANKS BUT WILL NQ"TRUN
5.OL (VIM E) "F"" SERlES (TBI)
Circuit Description:
This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in
the tank.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. A "Service Engine Soon" light "ON" is a basic test
to determine if there is a 12 volt supply and
ignition 12 volts to ECM. No
ALIII, may be due to
an ECM problem and CHART A-2 will diagnose
the ECM. If TPS is over 2.5 volts, the engine may
be in the clear flood mode, which will cause
starting problems.
2. No spark may be caused by one of several
components related to the ignition system.
CHART
C-4 will address all problems related to
the causes of a no spark condition.
3. Fuel spray from the injector(s) indicates that fuel
is available. However, the engine could be
severely flooded due to too much fuel.
4. While cranking engine, there should be no
f~lel
spray with injector disconnected. Replace an
injector if it sprays fuel or drips like a leaking
water faucet.
5, The fuel pressure will drop after the fuel pump
stops running due to
a controlled bleed in the fuel
system. Use
of the fuel pressure gage will determine
if fuel
system pressure is enough for the engine to start
and run. The key may have to be cycled
2 or more
times for accurate reading.
6. No fuel spray from injector indicates a faulty fuel
system or no ECM control of injector.
7. This test will determine if the ignition module is
not generating the reference pulse if the wiring or
ECM is at fault. By touching and removing
a test
light to 12 volts on CKT 430,
a reference pulse
should be generated. If
injector test light blinks,
the ECM and wiring are
OK.
Diagnost Aids:
@ Water or foreign material can cause a no start
during freezing weather.
@ An EGR sticking open can cause a low airlfuel
ratio during cranking.
@ Fuel pressure: Low fuel pressure can result in
a very lean airlfuel ratio. See CHART A-7.
@ A grounded CKT 423 (EST) may cause a "No-
Start" or a "Start then Stall" condition.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6E2-A-15
CHART A-3
RECONNECT SPARK PL
CONNECTOR.
AIDS" ON FACING
CONNECTION AT
"85" OR FAULTY ECM.

CHART A-3
(Page 2 of 2 )
ENGINE CRANKS BUT WILL NOT RUN
5.OL (VIN E) "F'XSERIES (TBI)
Circuit Description:
This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in
the tank.
Test Description: Numbers below refer to circled 2.
numbers on the diagnostic chart.
1. No fuel spray from one injector indicates a faulty
fuel injector or no ECM control of injector. If the
test light "blinks" while cranking, then
ECM
control should be considered OK. Be sure test
light makes good contact between connector
terminals during test.
The light may be a little
dim when "blinking". This is due to current draw
of the test light. How bright it "blinks" is not
important. However, the test light should be
a BT
8320 or equivalent.
CKTs 481 and 482 supply ignition voltage to the
injectors. Probe each connector terminal with a
test light to ground. There should be a light on at
one terminal.
If the test light confirms ignition
voltage at the connector, the ECM injector control
CKT 467 or 468 may be open. Reconnect the
injector, and using a test light connected to
ground, check for a light at the applicable ECM
connector terminal
("D14" or "D16"). A light at
this point indicates that the injector drive circuit
involved is OK.
If an ECM repeat failure has occurred, the injector
is shorted. Replace the injector and ECM.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) 6EZ-A-17
, .... ... .. ... s
: FROM

6EZ-Pa-18 5.OL (VIN E) DRIVEABILITY AND EMISSIONS
FUEL PUMP
RELAY CONN.
465 DK GRNMIHT
450 BLWHT
FUEL PUMP
BATTERY JUNCTION TEST TERM. BULKHEAD BODY CONNECTOR
BLOCK
(1 2 VOLT) CONNECTOR
CHART A-7
(Page 1 of 2)
FUEL SYSTEM DlAGNOSlS
5.0L (VIN E) "F"" SERIES (TBI)
Circuit Description:
When the ignition switch is turned "ON", the electronic control module (ECM) will turn "ON" the in-tank
fuel pump. It will remain "ON"
as long as the engine is cranking or running, and the ECM is receiving ignition
reference pulses.
If there are no reference pulses, the ECM will shut
"OI'F" the fuel pump within 2 seconds after key "ON".
The pump will deliver fuel to the THI unit, where the system pressure is controlled to 62 to 90 kPa (9 to 13
psi). Excess fuel is then returned to the fuel tank.
The fuel pump test terminal is located in the left side of the engine compartment. When the engine is
stopped, the pump can be turned "ON" by applying battery voltage to the test terminal.
lest Description: Numbers below refer to circled Diagnostic Aids:
numbers on the diagnostic chart
1. Fuel pressure should be noted while fuel pump is Improper fuel system pressure can result in one of
running. Fuel pressure will drop immediately the following symptoms:
after fuel pump stops running due to a controlled
e Cranks, but won't run.
bleed in the fuel system.
@ Code 44.
@ Code 45.
@ Cuts out, may feel like ignition problem.
@ Poor fuel economy, loss of power.
FIesitation.

DRIVEABILITY AND EMISSIONS 5.8L (VIN E) 6E2-A-19
- PLUGGED PUMP INLET FILTER.

6EZ-A-20 5.0L (VIN E) DRIVEABILITY AND EMISSIONS
FUEL PRESSURE
CHART A-7
(Page 2 of 2)
FUEL SYSTEM DIAGNOSIS
5.OL (VIN E) "F" SERIES (TBI)
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Pressure, but less than 62 kPa (9 psi) falls into two
areas:
@ Pressure less than 62 kPa (9 psi). Amount of
fuel to injectors
OK but, pressure is too low.
System will be lean and may set Code
44.
Also, hard starting cold and poor overall
performance. Restricted flow causing pressure drop.
Normally, a vehicle with a fuel pressure of less
than 62
kPa (9 psi) at idle will not he
driveable. However, if the pressure drop
occurs only while driving,
the engine will
surge then stop as pressure begins to drop.
2. Restricting the fuel return line allows the fuel
pump to develop its maximum pressure (dead head
pressure). When battery voltage is applied to the
pump test terminal, pressure should be from
90 to
124
kPa (13 to 18 psi).
3. This test determines if the high fuel pressure is
due to a restricted fuel return line or a throttle
body pressure regulator problem.

DRIVEABILITY AND EMISSIONS 5.OL (VIN E) CEZ-A-21
@ DISCONNECT FUEL RETURN LlNE
FLEXIBLE HOSE.
ATTACH
5/16 1.D. FLEX HOSE TO
THROTTLE BODY SIDE OF RETURN LINE.
INSERT THE OTHER END IN AN APPROVED
GASOLINE CONTAINER.
r NOTE FUEL PRESSURE WITHIN 2 SECONDS
@ APPLY 12 VOLTS TO FUEL
CHECK FOR RESTRICTED
FUEL RETURN
LlNE FROM
THROTTLE BODY.
CLEAR CODES AND CONFIRM "CLOSED LOOP
" OPERATION AND NO "SERVICE ENGINE SOON" LIGHT.