1988 PONTIAC FIERO fuel pump

6A2-16 2.8 LITER V-6
Figure 6A2-19 Camshaft Timing
2. Align dowel in camshaft with dowel hole in
camshaft sprocket, then install sprocket on
camshaft.
3. Draw the camshaft sprocket onto camshaft using
the mounting bolts. Torque to specifications.
4. Lubricate timing chain with engine oil.
5. Install crankcase front cover as previously
outlined.
Figure 6A2-20 Measuring Camshaft Lobe Lift
CAMSHAFT
Measuring Lobe Lift Procedure is similar to that
used for checking valve timing. If improper valve
operation is indicated, measure the lift of each push rod
in consecutive order and record the readings.
1. Remove the valve mechanism, as previously
outlined.
2. Position
indicator with ball socket adapater (Tool
5-8520) on push rod. Make sure push rod is in the
lifter socket.
3. Rotate the crankshaft slowly in the direction of
rotation until the lifter is on the heel of the cam lobe.
At this point, the push rod is in its lowest
position.
4. Set the dial indicator on zero, then rotate the
crankshaft slowly, or attach an auxiliary starter
switch and "bump" the engine over, until the
push rod is in the fully raised position (Figure
6A2-20).
CAUTION: Whenever the engine is
cranked remotely at the starter, with
a special jumper cable or other means,
the distributor primary lead must be
disconnected from the coil to prevent
electrical shock.
5. Compare the total lift recorded from the dial
indicator with the specifications.
6. If camshaft readings for all lobes are within
specifications, remove dial indicator assembly.
7. Install and adjust valve mechanism, as previously
outlined.
Removal
1. Remove valve lifters as previously outlined.
2. Remove crankcase front cover as previously
outlined.
3. Remove fuel pump and push rod.
4. Remove timing chain and sprocket as previously
outlined.
5. Remove camshaft.
NOTICE: All camshaft journals are the same
diameter and care must be exercised in removing
camshaft to avoid damage to bearings.
Inspection
The camshaft bearing journals should be
measured with a micrometer for an out-of-round
condition. If the journals exceed
.025mm out-of-round,
the camshaft should be replaced.
Installation
Whenever a new camshaft is installed, coat
camshaft lobes with
GM E.O.S, or equivalent.
Whenever a new camshaft is installed, install new
oil, new filter and replacement of all valve lifters is
recommended to insure durability of the camshaft
lobes and lifter feet.
1. Lubricate camshaft journals with engine oil and
install camshaft.
2. Install timing chain, as previously outlined.
3. Install fuel pump push rod and fuel pump.
4. Install crankcase cover, as previously outlined.
5. Install
lifters, as previously outlined.
6. Complete build up of engine.
CAMSHAFT BEARINGS
Removal
Camshaft bearings can be replaced while engine
is disassembled for overhaul or without complete
disassembly of the engine. To replace bearings without
complete disassembly remove the camshaft and
crankshaft leaving cylinder heads attached and pistons
in place. Before removing crankshaft, tape threads of

2.8 LITER V-6 6A2-25
Fitting
1. Select rings comparable in size to the piston being
used.
2. Slip
the compression ring in the cylinder bore;
then press the ring down into the cylinder bore
about 6mm above ring travel. Be sure ring is
square with cylinder wall.
3. Measure the space or gap between the ends of the
ring with a feeler gage (Figure
6A2-33).
4. If
the gap between the ends of the ring is below
specifications, remove the ring and try another
for fit.
5. Fit each compression ring to the cylinder in
which it is going to be used.
6. If the pistons have not been cleaned and inspected
as previously outlined, do so.
7. Slip the outer surface of the top and second
compression ring into the respective piston ring
groove and roll the ring entirely around the
groove (Figure
6A2-34). If binding occurs at any
point, the cause should be determined. If there is
a ring groove, remove by dressing with a fine cut
file. If the binding is caused by a distorted ring,
check a new ring.
Installation
1. Install oil ring spacer in groove being sure ends
are butted and not overlapped.
2. Hold
spacer ends butted and install lower steel oil
ring rail.
3. Install upper
steel oil ring rail with gap staggered.
4. Flex
the oil ring assembly to make sure ring is
free. If binding occurs, the cause should be
detemined. If caused by ring groove, remove by
dressing groove with a fine cut file. If binding is
caused by a distorted ring, check a new ring.
5. Install second compression ring. Stagger gap
from other rings.
6. Install top compression ring with gap properly
located.
ENGINE ASSEMBLY
Removal
Disconnect battery.
Remove air cleaner.
Remove hood. Drain radiator.
Remove lower radiator hose.
Remove upper fan shroud.
Remove upper radiator hose and coolant
recovery hose.
Remove transmission cooler lines. Remove radiator.
Remove fan assembly.
Remove heater hoses.
Disconnect carburetor linkage, includes cruise
control detent cable.
Remove vacuum brake booster line.
Remove distributor cap and lay wiring aside.
Disconnect necessary wires and hoses.
Remove power steering pump and lay aside. Raise
vehicle.
Remove exhaust pipes at exhaust manifold.
Remove dust cover.
Remove converter bolts.
Disconnect starter wires.
Remove bell housing bolts.
Remove motor mount through bolts.
Disconnect fuel lines at fuel pump.
Lower vehicle. Support transmission.
Remove
A.I.R./Converter pipes bracket.
Remove engine, include removing wire from
bracket at rear left of engine.
Installation
Position engine assembly in vehicle.
Attach motor mount to engine brackets and
lower engine in place.
Remove engine lifting device.
Remove transmission floor jack.
Raise vehicle on hoist.
Install mount "through" bolts. Torque to
specifications.
Install bell housing bolts. Torque to
specifications.
On vehicles with automatic transmission, install
converter to flywheel attaching bolts. Torque to
specifications.
Install flywheel splash shield of conveter housing
cover as applicable. Torque attaching bolts to
specifications.
Install starter wires.
Connect fuel lines.
Connect exhaust pipe at manifold.
Lower vehicle on hoist.
Reinstall power steering pump, if so equipped.
Connect necessary wires and hoses.
Install radiator and fan shroud and reconnect
radiator and heater hoses.
Fill cooling system.
Fill crankcase with oil. See owner's manual for
specifications.
Install air cleaner.
Install hood.
Connect battery cables.
NOTICE: To avoid possible arcing of battery,
connect positive battery cable first.
22. Start engine, check for leaks and check timing.
CRANKSHAFT
The crankshaft can be removed while the engine
is dissasembled for overhaul, as previously outlined or
without complete disassembly.
Removal
1. With the engine removed from the vehicle,
remove the clutch assembly (if equipped) and
flywheel. Mount engine in stand and clamp
securely.

6A3-2 V-8 ENGINE
VALVE TRAIN
A very simple ball pivot-type train is used.
Motion is transmitted from the camshaft through the
hydraulic lifter and push rod to the rocker arm. The
rocker arm pivots on its ball and transmits the
camshaft motion to the valve. The rocker-arm ball is
retained by a nut.
HYDRAULIC VALVE LIFTERS
Hydraulic Valve Lifters are used to keep all parts
of the valve train in constant contact.
The hydraulic lifter assembly consists of: a roller,
the lifter body, which rides in the cylinder block boss,
a plunger, a push rod seat, a metering valve, a plunger
spring, a check ball and spring, a check ball retainer
and a push rod seat retainer.
When the lifter is riding on the low point of the
cam, the plunger spring keeps the plunger and push rod
seat in contact with the push rod.
When the lifter body begins to ride up the cam
lobe, the check ball cuts off the transfer of oil from the
reservoir below the plunger. The plunger and lifter
body then rise as a unit, pushing up the push rod and
opening the valve.
As the lifter body rides down the other side of the
cam, the plunger follows with it until the valve closes.
The lifter body continues to follow the cam to its low
point, but the plunger spring keeps the plunger in
contact with the push rod. The ball check valve will then
move off its seat and the lifter reservoir will
remain full.
INTAKE MANIFOLD
The intake manifold for those engines with
carburetors are made of cast iron or aluminum double
level design for efficient fuel distribution. An Exhaust
Gas Recirculation (EGR) port is also cast into the
manifold for the mixture of exhaust gases with the fuel
air mixture.
The intake manifold for those vehicles equipped
with
PFI is a cast aluminum unit. It centrally supports
a fuel rail with
8 fuel injectors.
EXHAUST MANIFOLDS
Two cast iron exhaust manifolds are used to
direct exhaust gases from the combustion chambers to
the exhaust system. The left hand side manifold
receives a heat shield that is used to route heated air
to the air cleaner. for better fuel vaporization during
warm-up.
COMBUSTION CHAMBERS
Combustion Chambers are cast to insure uniform
shape for all cylinders. Spark plugs are located between
the intake and exhaust valves. The contoured wedge
shape of the combustion chamber minimizes the
possibility of detonation, facilitates breathing and
provides swirling turbulence for smooth, complete
combustion.
ENGINE LUBRICATION
Full pressure lubrication through a full flow oil through drilled passages, to the camshaft and
filter, is furnished by a gear-type oil pump. The crankshaft to lubricate the bearings. The valve lifter oil
distributor, driven by a helical gear on the camshaft,
gallery feeds the valve lifters which, through hollow
drives the oil pump. The main oil gallery feeds oil,
push rods, feed the individually mounted rocker arms.

V-8 ENGINE 6A3-7
-
3. Disconnect accelerator T.V. and cruise cables.
4. Remove air intake duct.
5. Disconnect coolant hoses at throttle body.
6. Disconnect wires at throttle body.
7. Disconnect vacuum and breather hoses at
throttle body.
8. Remove throttle body from plenum.
9. Remove distributor shield.
10. Disconnect brake vacuum hoses at plenum.
1 1. Disconnect vacuum hoses at plenum.
12. Refer to Section 6E3 for removal of:
a Plenum
Fuel Rail
a Cold Start Injector
e Runners
13. Remove distributor.
14. Disconnect EGR solenoid.
15. Disconnect all electrical wires that would
interfere.
16. Remove intake manifold bolts.
17. Remove intake manifold.
Installation
1. Clean all seal surfaces.
2. Install gaskets and place a 3/16 inch 5 (mm) bead
of RTV, No. 1052917 or
equivalent,on the front
and rear ridges of the cylinder case. Extend the
bead 1/2 inch
(13mm) up each cylinder head to
seal and retain the manifold side gaskets and
install intake manifold.
3. Torque manifold bolts to specified torque.
4. Reconnect electrical and vacuum wires.
5. Install distributor.
6. Refer to Section 6E3 for installation
of:
e Plenum
e Fuel Rail
e Cold Start Injectors
a Runners
7. Vacuum hoses at plenum.
8. Install distributor shield.
9. Install throttle body and related parts.
10. Fill cooling system.
1 1. Reconnect battery cable.
12. Start engine and look for leaks.
DIPSTICK TUBE
Removal
1.
Disconnect battery negative cable to prevent
possible contact of the dipstick tube with the
battery terminal on starter during removal.
2. Remove bolt attaching bracket to engine and
remove tube (loose fit).
lnstallation
1. Clean tube and apply sealant #I052080 or
equivalent, around tube
1/2" below bead.
2. Insert tube in block and rotate into position.
3. Install bolt (with starter brace on top of tube
bracket) and connect battery cable.
&LB9/LO3/L98
19-35 N.m (14-26 FT. LBS.)
27-43
N.m (20-32 FT. LBS.)
Fig. 6A3-5 Exhaust Manifold lnstallation
EXHAUST MANIFOLD
Removal (Right Side)
1. Disconnect battery negative cable.
2. Disconnect spark plug wires.
3. Disconnect
A.I.R. hoses.
4. Remove air management valve.
5. Raise vehicle.
6. Remove exhaust pipe nuts.
7. Lower vehicle.
8. Remove manifold bolts.
9. Remove exhaust manifold.
lnstallation
1. Clean
mating surfaces on manifold and head,
then install manifold in position and install bolts
finger tight.
2. Torque bolts to specifications.
3. Reverse removal procedures.
Removal (Left Side)
1. Disconnect battery negative cable.
2. Disconnect spark plug wires.
3. Disconnect A.I.R. hoses.
4. If equipped with
A/C, remove compressor and
lay aside.
5. Remove power steering pump and lay aside.
6. Loosen brackets.
7. Remove rear
A/C and power steering adjusting
bracket.
8. Remove lower power steering adjusting bracket.
9. Raise vehicle.

V-8 ENGINE 6A3.17
4. Set dial indicator on zero, then rotate the
crankshaft slowly, or attach an auxiliary starter
switch and "bump" the engine over, until the
push rod is fully raised position.
e Whenever the engine is cranked remotely at
the started, with a special jumper cable or
other means, the distributor primary lead
should be disconnected from the distributor
(coil).
5. Compare the total lift recorded from the dial
indicator with specifications.
6. If camshaft readings for all lobes are within
specifications, remove dial indicator assembly.
7. Install and adjust valve mechanism as outlined.
Removal
Fig. 6A3-30 Removing Camshaft
1.
Remove valve lifters as previously outlined.
2. Remove crankcase front cover as previously
outlined.
3. Remove grille.
4. Remove fuel pump push rod as outlined in
Section 6C.
5. Complete camshaft removal as follows:
e Sprocket is a light fit on camshaft. If
sprocket does not come off easily a light
blow on the lower edge of the sprocket (with
a plastic mallet) should dislodge the
sprocket.
6. Install two 5/16" - 18 x 4" bolts in camshaft bolt
holes then remove camshaft (fig. 6A3-30).
NOTICE: All camshaft journals are the same
diameter and care must be used in removing
camshaft to avoid damage to bearings.
Inspection
The camshaft bearing journals should be
measured with a micrometer for an out-of-round
condition. If the journals exceed
.001" out-of-round,
the camshaft should be replaced.
Installation
When a new camshaft is installed coat camshaft
lobes with "Molykote" or its equivalent. When a new
camshaft is installed, replacement of all valve lifters is
recommended to insure durability of the camshaft
lobes and lifter feet.
Fig. 6A3-3 1 Aligning Timing Marks
Lubricate camshaft journals with engine oil and
install camshaft.
Install timing chain on camshaft sprocket. Hold
the sprocket vertically with the chain hanging
down and align marks on camshaft and
crankshaft sprockets. (Refer to fig. 6A3-3 1).
Align dowel in camshaft with dowel hole in
camshaft sprocket then install sprocket on
camshaft.
Draw the camshaft sprocket onto camshaft using
the mounting bolts. Torque to specifications.
Lubricate timing chain with engine oil.
Install fuel pump push rod as outlined in Section
6C.
Install grille.
Install crankcase front cover as previously
outlined.
Install valve lifters as previously outlined.
CAMSHAFT BEARINGS
Removal
Camshaft bearings can be replaced with engine
completely or partially disassembled. To replace
bearings without complete disassembly remove the
camshaft and crankshaft leaving cylinder heads
attached and pistons in place. Before removing
crankshaft, tape threads of connecting rod bolts to
prevent damage to crankshaft. Fasten connecting rods
against sides of engine so they will not be in the way
while replacing camshaft bearings.
1. With camshaft and crankshaft removed, drive
camshaft rear plug from cylinder block.
2. Using Tool J-6098, with nut and thrust washer
installed to end of threads, index pilot in camshaft
front bearing and install puller screw through
pilot.
3. Install remover and installer tool with shoulder
toward bearing, making sure a sufficient amount
of threads are engaged.
4. Using two wrenches, hold puller screw while
turning nut. When bearing has been pulled from

V-8 ENGINE 6A3-27
3. When finish honing
a cylinder bore to fit a piston,
the hone should be moved up and down at a
sufficient speed to obtain very fine uniform
surface finish marks in a cross-hatch pattern of
approximately
45" to 65" included angle. The
finish marks should be clean but not sharp, free
from imbedded particles and torn or folded
metal.
4. Permanently mark
the piston for the cylinder to
which it has been fitted and proceed to hone
cylinders and fit the remaining pistons.
NOTICE: Handle the pistons with care and do not
attempt to force them through the cylinder until
the cylinder has been honed to correct size as this
type piston can be distorted through careless
handling.
5. Thoroughly
clean the bores with hot water and
detergent. Scrub well with a stiff bristle brush and
rinse thoroughly with hot water. It is extremely
essential that a good cleaning operation be
performed. If any of the abrasive material is
allowed to remain in the cylinder bores, it will
rapidly wear the new rings and cylinder bores in
addition to the bearings lubricated by the
contaminated oil, the bores should be swabbed
and then wiped with a clean dry cloth. Cylinder
should not be cleaned with kerosene or gasoline.
Clean the remainder of the cylinder block to
remove the excess material spread during the
honing operation.
Piston Selection
1. Check USED piston to cylinder bore clearance as
follows:
a. Measure
the "Cylinder Bore Diameter"
with a telescope gage
"2-1/2" (64mm) from
top of cylinder bore").
b. Measure
the
"Piston Diameter" (at skirt
across center line of piston pin).
c. Subtract
piston diameter from cylinder bore
diameter to determine "Piston to Bore
Clearance".
d. Determine if piston to bore clearance is in
the acceptable range.
2. If
used piston is not acceptable, check Piston Size
Chart and determine if a new piston can be
selected to fit cylinder bore within the acceptable
range.
3. If
cylinder bore must be reconditioned, measure
new piston diameter (across center line of piston
pin) then hone cylinder bore to correct clearance
(preferable range).
4. Mark the piston to identify the cylinder for which
it was fitted.
OIL FILTER BYPASS VALVE
Inspection and Replacement
With the oil filter removed, check the spring and
fibre valve for operation. Inspect for a cracked or
broken valve. If replacement is necessary, the oil filter
adapter and bypass valve assembly must be replaced as an
assembly. Clean valve chamber in cylinder block
thoroughly. Torque retaining screws to specifications.
ENGINE ASSEMBLY
Removal
1. Disconnect battery.
2. Remove air cleaner.
3. Remove hood.
4. Drain radiator.
5. Remove lower radiator hose.
6. Remove upper fan shroud.
7. Remove upper radiator hose and coolant
recovery hose.
8. Remove transmission cooler lines.
9. Remove radiator.
10. Remove fan assembly.
1 1. Remove heater hoses.
12. Disconnect
carburetor linkage, includes cruise
control detent cable.
13. Remove vacuum brake booster line.
14. Remove
distributor cap and lay wiring aside.
15. Disconnect necessary wires and hoses.
16. Remove power steering
pump and lay aside.
17. Raise vehicle.
18. Remove exhaust
pipes at exhaust manifold.
19. Remove dust cover.
20. Remove converter bolts.
2 1. Disconnect starter wires.
22. Remove bell housing bolts.
23. Remove
motor mount through bolts.
24. Disconnect fuel lines
at fuel pump.
25. Lower vehicle.
26. Support transmission.
27. Remove
A.I.R./Converter pipe bracket.
28. Remove engine, include removing wire
from
bracket at rear left of engine.
Installation
1. Position engine
assembly in vehicle.
2. Attach
motor mount to engine brackets and
lower engine in place.
3. Remove engine lifting device.
4. Remove transmission floor jack.
5. Raise vehicle on hoist.
6. Install mount "through" bolts. Torque to
specifications.
7. Install bell housing bolts. Torque to
specifications.
8. On vehicles with automatic transmissions, install
I
converter to flywheel attaching bolts. Torque to
specifications.
9. Install flywheel splash shield of converter
housing cover as applicable. Torque attaching
bolts to specifications.
I
10. Install starter wires.
1 1. Connect fuel lines.
12. Connect exhaust pipe at manifold.
13. Lower vehicle on hoist.
14. Reinstall power steering pump, if so equipped.
15. Connect necessary wires and hoses.

ENGINE FUEL BC-1
SECTION 6C
NE FUEL
CONTENTS
General Description ..................................... 6C-1 Fuel
Cap ........................................................... 6C-3
.................................................. ............................................. Alcohol-In-Fuel 6C- 1 Fuel Filter Neck 6C-3
................... ............ Fuel Metering .................................................. 6C-2 Fuel Gage Sending Unit .. 6C-4
....................... ............................... Throttle Body Injection (TBI) .... 6C-2 Diagnosis ,. 6C-4 ................... Service
Procedures ............................................. 6C-4
Port Fuel Injection ...................................... 6C-2
Pressure Relief ........................................... 6C-4
Fuel Feed and Return Pipe
............................... 6C-2
Flow Test .................................................... 6C-4
Fuel Pipes (MPFI)
.......................................... 6C-3
Pressure Test - TBI ................................... 6C-4
Fuel and Vapor Hoses
....................................... 6C-3
Pressure Test - MPFI .................................... 6C-4
Fuel Pump ........................................................ 6C-3 ...................................................... Fuel Pump Relay .............................................. 6C-3 Fuel Tank 6C-4
Fuel Filter
......................................................... 6C-3 Accelerator Controls ...................................... 6C-5
Fuel Tank
....................................................... 6C-3
All new General Motors vehicles are certified by
the United States Environmental Protection Agency as
conforming to the requirements of the regulations for
the control of air pollution from new motor vehicles.
This certification is contingent on certain adjustments
being set to factory standards. In most cases, these
adjustment points either have been permanently
sealed and/or made inaccessible to prevent
indiscriminate or routine adjustment in the field. For
this reason, the factory procedure for temporarily
removing plugs, caps, etc., for purposes of servicing the
product must be strictly followed and, wherever
practicable, returned to the original intent of the
design.
GENERAL DESCRIPTION
All gasoline engines are designed to use only
unleaded gasoline. Unleaded gasoline must be used for
proper emission control system operation. Its use will
also minimize spark plug fouling and extend engine oil
life. Using leaded gasoline can damage the emission
control system and could result in loss of emission
warranty coverage.
All cars are equipped with an Evaporative
Emission System. The purpose of the system is to
minimize the escape of fuel vapors to the atmosphere.
Information on this system will be found in Section
6E2, or 6E3.
When working on the fuel system, there are
several things to keep in mind.
@ Any time fuel system is being worked on,
disconnect the negative battery cable
except for those tests where battery
Adhere to all Notices and Cautions.
Always keep a dry chemical (Class B) fire
extinguisher near the work area.
-
Always use a backup wrench when loosening or
tightening a screw couple fitting.
The torque on a screw fitting is
30 N-m (22 lb.
ft.).
Pipe is used on all MPFI, TPI, SFI, and TBI
applications. Fittings require the use of an
"0"
Ring. Replace all pipe with the same type of pipe
and fittings that were removed.
All fuel pipes must meet GM Specification
124-M, or its equivalent.
All fuel hoses must meet GM Specification
6163-M, or its equivalent.
Do not replace fuel pipe with fuel hose.
voltage is required.
@ On MPFI, TPI, SF1 and TBI systems, always A1cohol-ln-Fuel
relieve the line pressure before servicing any fuel Certain driveability complaints such as
system components. hesitation, lack of power, stall, no start, etc., may be
@ Do not repair the fuel system until you have read caused
by an excessive amount of alcohol-in-fuel. The
the copy and checked the illustrations relating to complaints
may be due to fuel system corrosion and
that repair. subsequent
fuel filter plugging, deterioration of rubber

6C-2 ENGINE FUEL
components such as the accelerator pumps and/or
air-fuel mixture leaning effects.
Various types and concentrations of alcohols are
used in commercial gasoline. Some alcohols are more
detrimental to fuel system components than others. If
an excessive amount of alcohol in the fuel is suspected
as the cause of a driveability condition, the following
procedure may be used to detect the presence of
alcohol in the fuel.
In this procedure, water is used to
extract the alcohol from the fuel. However, the specific
type of alcohol is not determined.
The fuel sample should be drawn from the
bottom part of the tank so that any water, if already
present, can be detected. The sample should be bright
and clear. If the sample appears cloudy or
contaminated with water as indicated by a water layer
in the bottom part of the sample, this procedure should
not be used. The fuel system should then be cleaned
(See Fuel System Cleaning).
Testing Procedure
1. Using a 100 ml cylinder with 1 ml graduation
marks, fill with fuel to the 90 ml mark.
2. Add 10 ml of water to bring the total fluid volume
to 100 ml and install a stopper.
3. Shake vigorously for 10 to 15 seconds.
4. Carefully loosen stopper to release pressure.
5. Close the stopper and shake vigorously again for
10 to 15 seconds.
6. Carefully loosen
stopper to release pressure.
7. Put the graduated cylinder on a level surface for
approximately 5 minutes to allow adequate liquid
separation.
If alcohol is present in the fuel, the volume of the
lower layer, which would now contain alcohol and
water will be greater than 10 ml. For example, if the
volume of the lower layer is increased to 15 ml, it
would indicate at least 5 percent alcohol in fuel. The
actual amount of alcohol may be somewhat greater
because this procedure does not extract all of the
alcohol from the fuel.
FUEL METERING
Throttle Body lnjection
(TBI)
With Throttle Body Injection (TBI), an injection
unit is placed on the intake manifold where the
carburetor is normally mounted. The TBI unit is
computer controlled and supplies the correct amount
of fuel during all engine operating conditions. See
Section 6E2 for information relative to operation and
diagnosis of TBI units.
Port Fuel lnjection
The ECM is in complete control of this fuel
delivery system during all driving conditions.
The intake manifold is used only to let air into the
engine. Fuel is injected by separate injectors that are
mounted over the intake valve.
With the Port Injection System, there is no need
for a Thermac, EFE, Map Sensor, Baro Sensor, A.I.R.
System, or Dual Bed Converter. This
system provides better cold driveability,
lower exhaust emissions and better throttle response.
In Sequential Fuel Injection systems (SFI),
injectors turn on at every crankshaft revolution. The
ECM controls the injector "on" time so that the
correct amount of fuel is metered, depending on
driving conditions.
Two interchangeable
"0" rings are used on the
injector that must be inspected when the injectors are
removed. Check
"0" rings for cuts or other type of
damage and replace as necessary.
The air cleaner is remotely mounted near the
radiator. It is connected to the intake manifold by air
intake ducting.
Also, mounted between the air cleaner and
intake, are the mass air flow sensor and throttle body.
Cold driveability characteristics are greatly
improved with the aid of an engine coolant supply to
the throttle body for rapid warm up.
The throttle body design uses an integral Idle Air
Control to govern idle speed and a Throttle Position
Sensor (TPS). The IAC and TPS are both controlled
by the ECM.
A large diameter fuel rail is attached to the intake
manifold and supplies fuel to all the injectors.
A fuel pressure tap is located on the rail for quick
pressure checks.
Fuel is recirculated through the rail continually
while the engine is running. This removes air and
vapors from the fuel as well as keeping the fuel cool
during hot weather operation.
A fuel pressure regulator is mounted on the fuel
rail. It maintains a constant 36 psi pressure across the
injectors under all operating conditions. It is
accomplished by controlling the amount of fuel that is
recirculated back to the fuel tank, based on engine
demand.
The pressure regulator also uses an
"0" ring for
attachment. The
"0" ring used is the same one that is
used for the injectors.
Some engines also have an accumulator that is
located in the fuel feed line near the cowl area. It is used
to dampen the vibration that is caused by the
pressurized fuel and the pulsing of the injector.
See Section 6E3 for more information and
diagnosis.
Fuel Feed and Return Pipe
When replacing fuel feed and return pipes, always
replace them with welded steel tubing meeting GM
Specification
124M, or its equivalent. The replacement
pipe must use the same type of fittings as the original
pipes to ensure the integrity of the connection.
NOTICE: Do not replace fuel pipe with fuel hose
or any other type of tubing such as copper or
aluminum. Only tubing meeting the 124M
specification is capable of meeting all the pressure
and vibration characteristics necessary to ensure
the durability standard required.
Always check and replace any
"0" rings or
washers that appear damaged.