1988 PONTIAC FIERO Service Repair Manual

6E3-A-14 5.0L (VIN F) & 5.7L (VIN 8) DRIVEABILITY AND EMISSIONS
CHART A-3
(Page 1 of 2)
ENGINE CRANKS BUT WON'T RUN
5.OL (VIN F) & 5.7L (VIN 8) "F" SRIES (PORT)
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 Diagnostic Aids:
numbers on the diagnostic chart.
1. A "Service Engine Soon" light "ON" is a basic test @ An EGR valve sticking open can cause a low
to determine if there is a
12 volt supply and airlfuel ratio during cranking. Unless
engine
ignition
12 volts to ECM. No ALDL may be due to enters
"Clear Flood" at the first indication of a
an ECM problem and CHART
A-2 will diagnose flooding
condition, it can result in a no start.
the ECM. If TPS is over
2.5 volts the engine may @ Check for fouled plugs.
be in the clear flood mode which will cause
@ A defective cold start circuit or water in fuel line
starting problems. The engine
will not start can
cause a no start in cold weather. See
CHART
without reference pulses and therefore the "Scan" A-9.
should read rpm (reference) during crank. @ A defective MAF Sensor may cause a no start or a
2. No spark may be caused by one of several stall
after start. To determine if the sensor is
components related to the Ignition System. causing
the problem, disconnect it. The
ECM will
CHART C-4 will address all problems related to then
use a default value for the sensor, and if the
the causes of a no spark condition. condition
is corrected and the connections are
OK,
3. The test light should blink, indicating the ECM is replace the sensor.
controlling the injectors ok. How bright the light
@ rllso check that injectors on both sides of engine
blinks is not important. However, the test light
will cause a test light to "blink". If not OK, check
should be a
5-34730-3 or equivalent. injector fuses.
4. Use fuel
pressure gage 5-34730-1 or equivalent. If al~ove are all OK, refer to "Symptoms" it1
Wrap a shop towel around the fuel pressure tap to Scction "R". Ilard Start.
absorb any small amount of fuel leakage that may
occur when installing the gage.

DRIVEABILITY AND EMISSIONS 5.0L (VIN F) & 5.7L (VIN 8) 6E3-A-15
USE CHART A-1. r INSTALL "SCAN" TOOL. IF "NO ALDL", USE CHART A-2.
CHECK THE FOLLOWING:
IF A CODE
46 OR 54 IS SET, REFER TO APPLICABLE CHART.
TPS -IF OVER 2.5 VOLTS AT CLOSED THROTTLE, USE THE
CODE 21 CHART.
IS RPM
IDICATED D
1-34730-2 OR EQUIVALENT 4-WAY CONNECTOR.
TO INJECTOR HARNEES
r IGNITION "ON".
CONNECTOR.
r MOMENTARILY TOUCH
CHECK FOR BLINKING LIGHT HARNESS CONNECTOR
TERMINAL (CKT
430) WITH A
ST IS PERFORMED.
I USECHARTA-3 I
I (2 OF 2) I L ----------- J

6E3-A-16 S.OL (VIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
430 PPWHT
PRIMARY COIL
CHART A-3
(Page 2 of 2)
ENGINE CRANKS BUT WONT RUN
5.OL (VIN F) & 5.71 (VIN 8) "F" SERIES (PORT)
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Checks for 12 volt supply to injectors. Due to the
injectors wired in parallel there should be a light
"ON" on both terminals.
2. Checks continuity of CKT 467 and 468.
3. All checks made to this point would indicate that
the ECM is at fault. However, there is a
possibility of CKT 467 or 468 being shorted to a
voltage source either in the engine harness or in
the injector harness.
'Po test for this condition:
@ Llisconnect all injectors
Ignition
"ON".
@ Probe CKTs 467 and 468 on the ECM side of
injector harness with a test light connected to
ground.
('rest one injector harness on each
side of engine). There should be no light. If
light is
"on" repair short to voltage.
If OK, check the resistance of the injectors.
o Should be 10 ohms or more.
s Check injector harness connector. Be sure
terminals are not backed out of connector and
contacting each other.
o If all OK, replace ECM.

DRIVEABILITY AND EMISSIONS %.OL(VlN F) & 5.7L(VIN 8) 6E3-A-17
@ PROBE INJECTOR HARNESS
TERMINALS
WITH A TEST LlGHT TO
@ LIGHT SHOULD BE "ON" AT BOTH
DUE TO INJECTORS WIRED IN REPAIR
OPEN IN INJECTOR
PARALLEL, THERE SHOULD BE A
LIGHT ON BOTH TERMINALS.

6E3-A-18 5.OL (WIN F) & 5.7L(VIN 8) DRIVEABILITY AND EMISSIONS
PRESSURE REGULATOR
COLD START
TUBE ASSEMBLY
FUEL PRESSURE
LINE
CHART A-7
(Page 1 of 2)
FUEL SYSTEM DIAGNOSIS
5.OL (VIN F) & 5.7L (VIN 8) 'TF'3SERlES (PORT)
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
reference pulses. If there are no reference pulses, the ECM will shut "OFF" the fuel pump within 2 seconds after
ignition "ON" or engine stops.
The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system
pressure is controlled at 234 to 325
kPa (34 to 47 psi). Excess fuel is then returned to the fuel tank.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Wrap a shop towel around the fuel pressure
connector to absorb any small amount of fuel
leakage that may occur when installing the gage.
Ignition "ON", pump pressure should be 280-325
KPa (40.5-47 psi). This pressure is controlled by
spring pressure within the regulator
assenlbly
2. When the engine is idling, the manifold pressure
is low (high vacuum) and is applied to the fuel
regulator diaphragm. This will offset
the spring
and result in a lower fuel
pressure.This idle
pressure will vary somewhat depending on
barometric pressure; however, the pressure idling
should be less, indicating pressure regulator
control.
3. Pressure that continues to fall is caused by one of
the following:
In-tank fuel pump check valve not holding.
@ Pump coupling hose or pulsator leaking
@ Fuel pressure regulator valve leaking
Injector(s) sticking open.
4. An
injector sticking open can best be determined
by checking for a fouled or saturated spark
plug(s).
If a leaking injector cannot be determined by a
fouled or saturated spark plug, the following
procedure should be used:
@ Remove Plenum, and remove fuel rail bolts.
Follow the procedures in the Fuel Control
Section of this manual, but leave fuel lines
connected.
s Lift fuel rail out just enough to observe
injector nozzles in the ports.
CAUTION: BE SURE INJECTOR(S) ARE NOT ALLOWED
TO SPRAY ON ENGINE AND THAT INJECTOR
RETAINING CLIPS ARE INTACT.
THIS SHOULD BE
CAREFULLY FOLLOWED TO PREVENT FUEL SPRAY ON
ENGINE WHICH WOULD CAUSE A
FIRE HAZARD.
@ Pressurize the fuel syste~rl and observe injector
nozzles.

: THIS CHART ASSUMES a CHART m THERE IS NO CODE 54
m PAGE 1.
THE IGNITION MA Y HA
VE TO BE CYCLED "ON"
RESSURE, WITH PUMP RUNNING SHOULD BE MORE
THAN ONCE TO OBTAIN MAXIMUM
(40.5-47 psi) AND HOLD STEADY WHEN PUMP PRESSURE.
ALSO, ITlS NORMAL FOR THE PRESSURE TO DROP SLIGHT1 Y WHEN THE PUMP STOPS.
10 SECONDS.
...... I
@ LEAKING PUMP
@ PLUGGED PUMP INLET FILTER.
RESTRICTED FUEL LINE.

TEST CONNECTOR PRESSURE REGULATOR
COLD START
VALVE AND
TUBE ASSEMBLY
FUEL PRESSURE
LINE
PUMP INLET FlLTE
CHART A-7
(Page 2 of 2)
FUEL SYSTEM DIAGNOSIS
5.OL (VIN F) & 5.7L (VIN 8) "F" SERIES (PORT)
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Fuel pressure less than 280 kPa (40.5 psi) falls
into two areas:
Regulated pressure less than
280 kPa
(40.5 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
overall poor performance.
@ Restricted flow causing pressure drop -
Normally, a vehicle with a fuel pressure of less
than
165 kPa (24 psi) at idle will not be
driveable. However, if the pressure drop
occurs only while driving, the engine will
normally surge then stop running
as pressure
begins to drop rapidly. This is most likely
caused by
a restricted fuel line or plugged
filter.
2. Restricting the the fuel return line allows the fuel
pump to develop its maximum pressure (dead head
pressure). When battery voltage is applied to the
pump
tesl terminal, pressure should be above
414 kPa (60 psi ).
3. This test determines if the high fuel pressure is
due to
a restricted fuel return line or a pressure
regulator problem.

DRIVEABILITY AND EMISSIONS 5.0L (VIN F) & 5.7L (VIN 8) 6E3-A-21
NOTICE: THE FUEL SYSTEM IS UNDER PRESSURE. TO AVOID FUEL SPILLAGE,
REFER TO FIELD SERVICE PROCEDURES IN SECTION
"C2" FOR TESTING
OR MAKING REPAIRS REQUIRING DISASSEMBLY OF FUEL LINES OR
.m ...... -
SE TO PRESSURE
@ BLOCK FUEL RETURN LINE.
@ APPLY 12 VOLTS TO FUEL PUMP RELAY
HARNESS TERMINAL "A" OR TO THE
FAULTY IN-TANK
r FUELPUMP
@ COUPLING HOSE OR