PONTIAC FIERO 1988 Service Repair Manual

6E3-A-I8 2.8b (VIN 5) DRIVEABILITY AND EMISSIONS
PUMP INLET FILTER
IN-TANK PUMP
FUEL
PRESSURE CONNECTOR
CHART A-7
(Page 4 of 2)
FUEL SYSTEM DsAGNOSBS
2.8L (VIN S) ""FYSERBES (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
HE1
distributor reference pulses.
If there are no reference pulses, the ECM will shut "OFF" the fuel pump within
2 seconds after key "ON" or
engine stopped.
The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system
pressure is controlled to about 234 to 317
kPa (34 to 46 psi). Excess fuel is then returned to the fuel tank.
Test Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Use pressure gage 5-34730-1. Wrap a shop towel
around the fuel pressure tap 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 assembly.
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
was 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 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 can not be determined by a
fouled or saturated spark plug the following
procedure should be used.
e Remove Plenum, cold start valve and remove
fuel rail bolts. Follow the procedures in the
fuel control section of this manual, but leave
fuel lines connected.
@ Reconnect cold start valve.
@ Connect a hose to valve nozzle and insert into
a gasoline container.
@ Lift fuel rail out just enough to leave injector
nozzles in the ports.
CAUTION: BE SURE INJEePOR(S) ARE NOT ALLOWED
PO SPRAY ON ENGINE AND THAT INJECTOR
RETAINING
CLIPS ARE INTACT. PHIS SHOULD BE
CAREFULLY
FOLLOWD PO PREVENT FUEL SPRAY ON'
ElZIGlNE WHICH WOULD CAUSE A FIRE HAZARD.
@ Pressurize the fuel system.
@ I.if't each side of rail up and observe for
injc~ctot-l.) It.ulting

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-A-19
THIS CHART ASSUMES THERE IS NO
CODE
54
'OFF' FOR 10 SECONDS. AIC "OFF". ,,. . . . . . . . .'.
"ON". FUEL PUMP WILL RUN FOR ABOUT 2 : FROM :
THE IGNITIONMAY HAVE TO BE : A-3 : CYCLED "ON" MORE THAN ONCE
TO OBTAIN MAXIMUM PRESSURE.
ALSO, IT IS NORMAL FOR THE
PRESSURE TO DROP SLIGHTLY
WHEN THE PUMP STOPS.
AT NORMAL OPERATING
TEMPERATURE.
IGNITION "ON"
@ IGNITION "OFF".
BLOCK FUEL PRESSURE @ APPLY 12 VOLTS LINE BY PINCHING FLEX
TO FUEL PUMP
HOSE. PRESSURE TEST TERMINAL.
@ IGNITION "OFF" FOR 10 @ APPLY 10 INCHES OF VACUUM
LEAKING PUMP COUPLING
TO PRESSURE REGULATOR. @ IGNITION "ON".
INLET FILTER.

6E3-A-28 2.8b (VIN 9) DRIVEABILITY AND EMISSIONS
PUMP INLET FILTER
IN-TANK PUMP
FUEL PRESSURE CONNECTOR
CHART A-7
(Page 2 sf 2)
FUEL SYSTEM DIAGNOSIS
2.8L (VIN S) ""FYSEWlES (PORT)
Pest Description: Numbers below refer to circled
numbers on the diagnostic chart.
1. Pressure but less than 280
kPa (40.5 psi) falls into
two areas:
@ Regulated pressure, but less than 280 kPa
(40.5 psi). Amount of fuel to injectors OK but
pressure is too low. System will be lean
running 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 he
driveable. However,
if the pressure drop occurs only
while driving, the engine will normally surge
then stop as pressure begins to drop rapidly.
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 test 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 2.8b (VIM 5) 6E3-A-21
NOTICE: FUEL SYSTEM UNDER PRESSURE. TO AVOID FUEL SPILLAGE, REFER
TO FIELD SERVICE PROCEDURES FOR TESTING OR MAKING REPAIRS
REQUIRING DISASSEMBLY OF FUEL
LINES OR FITTINGS.
*....mam=4
@ ATTACH I.D. FLEX HOSE TO PRESSURE
REGULATOR SIDE OF RETURN LINE. INSERT THE
OTHER END IN AN APPROVED GASOLINE
ESSURE WITHIN
2 SECONDS AFTER

6E3-A-22 2.8L (VlN S) DRIVEABILITY AND EMISSIONS
COLD START FUEL INJECTION
SWITCH CONNECTOR
TO NEUTRAL START SWITCH
OR CLUTCH START SWITCH
- - COLD START FUEL
- CLOSED BELOW 35°C.
8 SEC. TIME LIMIT
COOLANT
CHART A-9
COLD START VALVE
2.8b (VIN S) ""FYSERIES (PORT)
Circuit Description:
The cold start valve is used to provide additional fuel during the crank mode to improve colt1 start-ups. This
circuit is important when engine coolant temperature is low because the other injectors are not pulsed
"ON"
long enough to provide the needed amount of fuel to start.
The circuit is activated only in the crank mode. The power is supplied directly from the starter solenoid and
is protected by a fuse. The system is controlled by
a cold start fuel injection switch which provides a ground path
for the valve during cranking when engine coolant is below
95°F (35°C).
The cold start fuel injection switch consists of a bimetal material which opens at a specified coolant
temperature. This bimetal is also heated by the winding in the switch which allows the valve to stay
"ON" for 8
seconds at -20°C (-5°F) coolant. The time the switch will stay closed varies inversely with coolant temperature.
In other words, as the coolant temperature goes
LIP, the cold start valve "ON" time goes down.
Pest Description: Numbers below refer to circled The amount of pressure drop depends on the
numbers on the diagnostic chart.
temperature of the engine.
1. Disconnecting the distributor 4-way connector 2. This test will determine the continuity through
will disable the other injectors. the switch to ground.

DRIVEABILITY AND EMlSSlONS 2.8b (VIN S) 6E3-A-23
GiNE FOR 2 SECONDS WHILE OBSERVING FUEL

6E3-A-24 2.8L (WIN 5) DRIVEABILITY AND EMISSIONS
OXYGEN ( 02) SENSOR
-
CODE 13
OXYGEN SENSOR CIRCUIT
(OPEN CIRCUIT)
2.8L (VIN S) ""FXSERlES (PORT)
Circuit Description:
The ECM supplies a voltage of about .45 volt between terminals "D6" and "D7". (If measured with a 10
megohm digital voltmeter, this may read as low as .32 volts.) The
02 sensor varies the voltage within a range of
about
1 volt if the exhaust is rich, down through about. 10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below 315" C
(600" F). An open sensor
circuit or cold sensor causes "Open Loop" operation.
Pest Description: Numbers below refer to circled
3 In doing this test use only a high impedence digital
numbers on the diagnostic chart.
volt ohmmeter. This test checks the continuity of
1. Code 13 will set:
CKTs 412 and 413 because if CKT 413 is open the @ Engine at normal operating temperature.
ECM voltage on CKT 412 will be over .6 volts (600 @ At least 2 minutes engine time after start. mV). @ 02 signal voltage steady between .35 and .55
volts.
@ Throttle position sensor signal above 4%.
@ All conditions must be met for about 60
seconds. If the conditions for a Code 13 exist the system
will not go "Closed Loop".
2. This will determine if the sensor is at fault or the
wiring or ECM is the cause of the Code 13.
Diagnostic Aids:
Normal "Scan" voltage varies between 1OOmV to
999mV (.1 and 1.0 volt) while in "Closed Loop".
Code
13 sets in one minute if voltage remains between .35
and .55 volts, but the system will go "Open Loop" in
about 15 seconds, Refer to "Intermittents" in Section
"R".

DRIVEABILITY AND EMISSIONS 2.8L (VIN 5) 6E3-A-25
OXYGEN SENSOR CIRCUIT
ODE 13 IS INTERMITTENT. IF NO
@ JUMPER HARNESS CKT 412 TO GROUND. DDlTlONAL CODES WERE STORED,
"SCAN" SHOULD DISPLAY
O2 VOLTAGE BELOW .2
VOLTS (200 mV) WITH ENGINE RUNNING.
CHECK VOLTAGE OF CKT
412 (ECM SIDE) AT O2
SENSOR HARNESS CONNECTOR USING A DVM.

6E3-A-26 2.8L (VIN 5) DRIVEABILITY AND EMISSIONS
4-WAY CONNECTOR
(REAR OF ENGINE) COOLANT SENSOR
AND MAT
CODE 14
COOLANT TEMPERATURE SENSOR CIRCUIT
(HIGH TEMPERATURE INDICATED)
2.8L (VIN S) ""F-SERIES (PORT)
Circuit Description:
The coolant temperature sensor uses a thermistor to control the signal voltage to the ECM. The ECM
applies a voltage on CKT 410 to the sensor. When the engine is cold the sensor (thermistor) resistance is high,
therefore the ECM will see high signal voltage.
As the engine warms, the sensor resistance becomes less, and the voltage drops.
At normal engine
operating temperature (85°C to 95°C) the voltage will measure about 1.5 to 2.0 volts.
Test Description: Numbers below refer to circled Diagnostic Aids:
numbers on the diagnostic chart.
1. Code 14 will set if:
Check harness routing for a potential short to ground
@ Signal voltage indicates a coolant in CKT 410. "SCAN" tool displays engine
temperature above 135°C (275°F) for
3 temperature in degrees centigrade. After engine is
seconds. started, the temperature should rise steadily to about
2. This test will determine if CKT 410 is shorted to
90°C then stabilize when thermostat opens. Refer to
ground, which will cause the conditions for Code
"Intermittents" in Section "B".
14.

DRIVEABILITY AND EMISSIONS 2.8L (VIN S) 6E3-A-27
CKT410 SHORTED TO GROUND.
CKT410 SHORTED TO SENSOR GROUND CIRCUIT.
FAULTY ECM.
DIAGNOSTIC AID
CLEAR CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NO "SERVICE ENGINE SOON" LIGHT.
COOLANT
SENSOR
TEMPERATURE TO RESISTANCE VALUES
(APPROXIMATE)
"F "C OHMS
210 100 185
160 70 450
100 38 1,800
70 20 3,400
40 4 7,500
20 -7 13,500
0 -1 8 25,000
-40 -40 100,700