1900 MITSUBISHI DIAMANTE oil pressure

ENGINEANDENGINEOVERHAUL 3-57
Anything that generates heat and/or friction WIII
eventually burn or wear out (for example, a light bulb
generates heat, therefore its life span is limited). With
this in mind, a running engine generates tremendous
amounts of both; friction is encountered by the mov-
ing and rotating parts inside the engine and heat is
created by friction and combustion of the fuel How-
ever, the engine has systems designed to help reduce
the effects of heat and friction and provide added
longevrty. The oiling system reduces the amount of
friction encountered by the moving parts inside the
engine, while the cooling system reduces heat cre-
ated by friction and combustion If either system is
not maintained, a break-down will be inevitable.
Therefore, you can see how regular maintenance can
affect the service life of your vehicle, If you do not
drain, flush and refill your cooling system at the
proper intervals, deposits WIII begin to accumulate in
the radiator, thereby reducing the amount of heat it
can extract from the coolant The same applies to
your oil and filter; If it is not changed often enough it
becomes laden with contaminates and is unable to
properly lubricate the engine. This increases friction
and wear.
There are a number of methods for evaluating the
condition of your engine. A compression test can re-
veal the condition of your pistons, piston rings,
cylinder bores, head gasket(s), valves and valve
seats. An oil pressure test can warn you of possible
engine bearing, or oil pump failures. Excessrve oil
consumption, evidence of oil in the engine air intake
area and/or bluish smoke from the tailpipe may indi-
cate worn piston rings, worn valve guides and/or
valve seals. As a general rule, an engine that uses no
more than one quart of oil every 1000 miles is in
good condition. Engines that use one quart of oil or
more in less than 1000 miles should first be checked
for oil leaks. If any oil leaks are present, have them
fixed before determining how much oil is consumed
by the engine, especrally if blue smoke is not visible
at the tailpipe
COMPRESSION TEST
# See Figure 226
tccs3801 Fig. 226 A screw-in type compression gauge
is more accurate and easier to use without
an assistant
A noticeable lack of engine power, excessive oil
consumption and/or poor fuel mileage measured
over an extended period are all indicators of internal
engine wear. Worn piston rings, scored or worn
cylinder bores, blown head gaskets, sticking or burnt
valves, and worn valve seats are all possible culprits.
A check of each cylinders compression WIII help lo-
cate the problem.
*A screw-in type compression gauge is
more accurate than the type you simply hold
against the spark plug hole. Although it takes
slightly longer to use, it’s worth the effort to
obtain a more accurate reading.
1 Make sure that the proper amount and vis-
cosity of engine oil is in the crankcase, then ensure
the battery is fully charged.
2. Warm-up the engine to normal operating
temperature, then shut the engine
OFF. 3. Disable the ignition system.
4. Label and disconnect all of the spark plug
wires from the plugs,
5. Thoroughly clean the cylinder head area
around the spark plug ports, then remove the spark
plugs.
6. Set the throttle plate to the fully open (wide-
open throttle) position You can block the accelerator
linkage open for this, or you can have an assistant
fully depress the accelerator pedal.
7. Install a screw-in type compression gauge
into the No. 1 spark plug hole until the fitting is snug.
Be careful not to crossthread the spark plug
hole.
8. According to the tool manufacturers instruc-
tions, connect a remote starting switch to the starting
circuit.
9. With the ignition switch in the
OFF position,
use the remote starting switch to crank the engine
through at least five compression strokes (approxi-
mately 5 seconds of cranking) and record the highest
reading on the gauge
10. Repeat the test on each cylinder, cranking the
engine approximately the same number of compres-
sion strokes and/or time as the first.
11. Compare the hrghest readings from each
cylinder to that of the others. The indicated compres-
sion pressures are considered within specifications if
the lowest reading cylinder is within 75 percent of the
pressure recorded for the highest reading cylinder
For example, if your highest reading cylinder pres-
sure was 150 psi (1034 kPa), then 75 percent of that
would be 113 psi (779 kPa). So the lowest reading
cylinder should be no less than 113 psi (779 kPa).
12. If a cylinder exhibits an unusually low com-
pression reading, pour a tablespoon of clean engine
oil into the cylinder through the spark plug hole and
repeat the compression test. If the compression rises
after adding oil, it means that the cylinder’s piston
rings and/or cylinder bore are damaged or worn, If
the pressure remains low, the valves may not be seat-
ing properly (a valve job is needed), or the head gas-
ket may be blown near that cylinder. If compression in any two adjacent cylinders is low, and if the addi-
tion of oil doesn’t help raise compression, there is
leakage past the head gasket. Oil and coolant in the
combustion chamber, combined with blue or con-
stant white smoke from the tailpipe, are symptoms of
this problem. However, don’t be alarmed by the nor-
mal white smoke emitted from the tailpipe during en-
gine warm-up or from cold weather driving. There
may be evidence of water droplets on the engine dip-
stick and/or oil droplets in the cooling system if a
head gasket is blown.
OIL PRESSURETEST
Check for proper oil pressure at the sending unit
passage with an externally mounted mechanical oil
pressure gauge (as opposed to relying on a factory
Installed dash-mounted gauge). A tachometer may
also be needed, as some specifications may require
running the engine at a specific rpm.
1. With the engine cold, locate and remove the oil
pressure sending unit.
2. Followrng the manufacturers instructions,
connect a mechanical oil pressure gauge and, if nec-
essary, a tachometer to the engine.
3 Start the engine and allow it to idle.
4 Check the oil pressure reading when cold and
record the number. You may need to run the engine
at a specified rpm, so check the specifications,
5. Run the engine until normal operating temper-
ature is reached (upper radiator hose will feel warm)
6. Check the oil pressure reading again with the
engine hot and record the number. Turn the engine
OFF. 7. Compare your hot oil pressure reading to that
given in the chart If the reading is low, check the
cold pressure reading against the chart. If the cold
pressure IS well above the specification, and the hot
reading was lower than the specification, you may
have the wrong viscosity oil in the engine. Change
the oil, making sure to use the proper grade and
quantity, then repeat the test.
Low oil pressure readings could be attributed to
internal component wear, pump related problems, a
low oil level, or oil viscosity that is too low. High oil
pressure readings could be caused by an overfilled
crankcase, too htgh of an oil viscosity or a faulty
pressure relief valve.
Now that you have determined that your engine is
worn out, you must make some decisions. The ques-
tion of whether or not an engine IS worth rebuilding
is largely a subjective matter and one of personal
worth. Is the engine a popular one, or IS it an obso-
lete model? Are parts available? Will it get acceptable
gas mileage once It is rebuilt? Is the car its being put
into worth keeping? Would it be less expensive to
buy a new engine, have your engine rebuilt by a pro,
rebuild it yourself or buy a used engine from a sal-
vage yard? Or would It be simpler and less expensive
to buy another car? If you have considered all these
matters and more, and have still decided to rebuild
the engine, then it is time to decide how you will re-
build it.

.
3-64 ENGINEANDENGINEOVERHAUL
There are only two types of valve guides used on
automobile engines: the replaceable-type (all alu-
minum heads) and the cast-in integral-type (most
cast iron heads). There are four recommended meth-
ods for repairing worn guides.
. Knurling
l Inserts l Reaming oversize l Replacing
Knurling is a process in which metal is displaced
and raised, thereby reducing clearance, giving a true
center, and providing oil control. It is the least ex-
pensive way of repairing the valve guides. However,
it is not necessarily the best, and in some cases, a
knurled valve guide will not stand up for more than
a short time. It requires a special knurlizer and pre-
cision reaming tools to obtain proper clearances. It
would not be cost effective to purchase these tools,
unless you plan on rebuilding several of the same
cylinder head.
Installing a guide insert involves machining the
guide to accept a bronze insert. One style is the coil-
type which is installed into a threaded guide. Another
is the thin-walled insert where the guide is reamed machined.
If the seats are in good condition, the valves can
be lapped to the seats, and the cylinder head assem-
bled. See the valves section for instructions on lap-
ping.
If the valve seats are worn, cracked or damaged,
they must be serviced by a machine shop. The valve
seat must be perfectly centered to the valve guide,
which requires very accurate machining.
CYLINDER HEAD SURFACE
If the cylinder head is warped, it must be ma-
chined flat. If the warpage is extremely severe, the
head may need to be replaced. In some instances, it
may be possible to straighten a warped head enough
to allow machining. In either case, contact a profes-
sional machine sh& for service. Cup Type Camshafl Followers
To install the springs, retainers and valve locks on
heads which have these components recessed into
the camshaft followers bore, you will need a small
I” .1.1.“1.“”
., ,, just after compressing the spring but before the *Any OHC cylinder head that shows exces-
sive warpage should have the camshaft bear-
ing journals align bored after the cylinder
head has been resurfaced. screwdriver-type tool, some clean white grease and a
lot of patience. You will also need the C-clamp style
spring compressor and the OHC tool used to disas-
semble the head.
1. Lightly lubricate the valve stems and insert all
of the valves into the cylinder head. If possible, main-
tain their original locations.
2. If equipped, install any valve spring shims
which were removed.
3. If equipped, install the new valve seals, keep-
ing the following in mind:
l If the valve seal presses over the guide,
lightly lubricate the outer guide surfaces.
l If the seal is an 0-rina tvoe. it rc rn+#fld
valve locks.
4. Place thevalve spring and retainer over the
stem.
5. Position the spring compressor and the OHC
tool, then compress the spring.
6. Using a small screwdriver as a spatula, fill
the valve stem side of the lock with white grease. Use
the excess grease on the screwdriver to fasten the
lock to the driver.
7. Carefully install the valve lock, which is stuck
to the end of the screwdriver, to the valve stem then
press on it with the screwdriver until the grease
squeezes out. The valve lock should now be stuck to
the stem.
8. Repeat Steps 6 and 7 for the remaining valve
lock. :
oversize to accept a split-sleeve insert. After the in-
sert is installed, a special tool is then run through the
guide to expand the insert, locking it to the guide.
The insert is then reamed to the standard size for
proper valve clearance.
Reamina for oversize valves restores normal clear- Failure to align bore the camshaft bearing
journals could result in severe engine dam-
age including but not limited to: valve and
oiston damage. connectinu rod damaoe,
iamshaft and/or crankshaft breakage,
antes and provides a true valve seat. Most cast-in
i tvpe guides can be reamed to accept an valve with an CRACKS AND PHYSICAL DAMAGE
oversize stem. The cost factor for this can become
quite high as you will need to purchase the reamer
and new, oversize stem valves for all guides which
were reamed. Oversizes are generally 0.003 to 0.030
in. (0.076 to 0.762mm), with 0.015 in. (0.381mm)
being the most common.
To replace cast-in type valve guides, they must be
drilled out, then reamed to accept replacement
guides, This must be done on a fixture which will al-
low centering and leveling off of the original valve
seat or quide, otherwise a serious guide-to-seat mis-
alignment may occur making it impossible to prop-
erly machine the seat.
Replaceable-type guides are pressed into the
cylinder head. A hammer and a stepped drift or
punch may be used to install and remove the guides.
Before removing the guides, measure the protrusion
on the spring side of the head and record it for instal-
tation. Use the stepped drift to hammer out the old
guide from the combustion chamber side of the head.
when in~llfng, determine whether or not the guide
also seals a water jacket in the head, and if it does,
use the ~o~ended sealing agent. If there is no
water jacket grease the valve guide and its bore. Use
the stepped drift, and hammer the new guide into the
cylinder head from the spring side of the cylinder
head. A stack af washers the same thickness as the
measured Eaton may help the installation Certain cracks can be repaired in both cast iron
and aluminum heads. For cast iron, a tapered
threaded insert is installed along the length of the
crack. Aluminum can also use the tapered inserts,
however welding is the preferred method. Some
physical damage can be repaired through brazing or
welding. Contact a machine shop to get expert advict
for your particular dilemma.
ASSEMBLY
+ See Figure 258
The first step for any assembly job is to have a
clean area in which to work. Next, thoroughly clean
all of the parts and components that are to be assem-
bled. Finally, place all of the components onto a suit-
able work space and, if necessary, arrange the parts
to their respective positions.
process.
VALVE SEATS
*Before any valve seat maChining can be
aerformed. the guides must be within factory
recommended specifications.
-
1 Fig. 258 Once assembled, check the valve
;
rlf any machtning or replacements were 1 clearance and correct as needed
I
made to the valve guides, the seats must be 9. Relieve the spring pressure slowly and insure
that neither valve lock becomes dislodged by the re-
tainer.
10. Remove the spring compressor tool.
11. Repeat Steps 2 through 10 until all of the
springs have been installed.
12. Install the followers, camshaft(s) and any
other components that were removed for disassem-
bly.
Rocker Arm Type Camshaft Followers
1. Lightly lubricate the valve stems and insert all
of the valves into the cylinder head. If possible, main-
tain their original locations.
2. If equipped, install any valve spring shims
which were removed.
3. If equipped, install the new valve seals, keep-
ing the following in mind:
l If the valve seal presses over the guide,
lightly lubricate the outer guide surfaces.
l If the seal is an O-ring type, it is installed
just after compressing the spring but before the
valve locks.
4. Place the valve spring and retainer over the
stem.
5. Position the spring compressor tool and
compress the spring.
6. Assemble the valve locks to the stem.
7. Relieve the spring pressure slowly and insure
that neither valve lock becomes dislodged by the re-
tainer.
8. Remove the spring compressor tool.
9. Repeat Steps 2 through 8 until all of the
springs have been installed.

ENGINEANDENGINEOVERHAUL 3-67
CONNECTING ROD
You should have the connecting rod checked for
StraiQhtness at a machine shop. If the connecting rod
is bent, it will unevenly wear the bearing and piston,
as well as place greater stress on these components.
Any bent or twisted connecting rods must be re-
placed. If the rods are straight and the wrist pin clear-
ance is within specifications, then only the bearing
end of the rod need be checked. Place the connecting
rod into a vice, with the bearing inserts in place, in-
stall the cap to the rod and torque the fasteners to
specifications. Use a telescoping gauge and carefully
measure the inside diameter of the bearings. Com-
pare this reading to the rods original crankshaft jour-
nal diameter measurement. The difference is the oil
clearance. If the oil clearance is not within specifica-
tions, install new bearings in the rod and take another
.
specifica- L
need to
shop as the pistons must be installed in the con measurement. it the Clearance is still out of :
tions, and the crankshaft is not, the rod will
be reconditioned by a machine shop.
*You can also use Plastigage’
@to check the
bearing clearances. The assen- . ...= - _______
Mm sectinn has complete instructions on its use.
Camshaft
Inspect the camshaft and lifters/followers as de
scribed earlier in this section.
Bearings
All of the enaine bearinos should be visuallv in-
~~~ I~ .- - -- ..-_-..,
spected for we; and/or damage. The bearing should
look evenly worn all around with no deep scores or
pits. If the bearing is severely worn, scored, pitted or
heat blued, then the bearing, and the components
that use it, should be brought to a machine shop for
block. ,ect
relationshipto the rod or engine damage can occur,
Pistons and Connecting Rods
I
b See Fiaute 264 --- --*------
Only pistons with the wrist pin retained by C-clips
are serviceable by the home-mechanic. Press fit pis-
tons require special presses and/or heaters to re- I”
rr
rove/install the connecting rod and should only be
PC srformed by a machine shop.
All pistons will have a mark indicating the direc-
tir 9n to the front of the engine and the must be in-
stalled into the engine in that manner. Usually it is a
notch or arrow on the top of the piston, or it may be
the letter F cast or stamped into the piston.
ASEtiBlY
1
crankshaft. Replace any freeze or oil galley plugs
which were removed during disassembly.
Crankshaft
u See Figures 265, 266, 267, and 266
1. Remove the main bearing inserts from the
block and bearing caps.
2. If the crankshaft main bearing journals have
been refinished to a definite undersize, install the
correct undersize bearina. Be sure that the bearina
inserts and bearing bores are clean. Foreign mateiial
under inserts will distort bearinq and cause failure.
3. Place the upper main bearing inserts in bores
*The oil holes in the bearing inserts must
be aligned with the oil holes in the cylinder
. . .
inspection. Full-circle bearings (used on most
camshafts, auxiliary shafts, balance shafts, etc.) re-
quire specialized tools for removal and installation, ’
and should be brought to a machine shop for service.
Oil Pump Before you begin assembling the engine, first give
yourself a clean, dirt free work area. Next, clean every
engine component again. The key to a QOOd assem-
hhr io da~nlinmw “‘I Ia ~rGiOllll,lc7.Ja. Mount the engine block into the engine stand and
II
*The oil pump is responsible fo
r providing wasn It one last time usmg water and detergent (dish-
unrhinn rldarnant ~nrirc well), While washing it, with a soft bristle brush and
: oil oassaoes. Comoletelv constant lubrication to the whole engine and 1ILl.M 0, ,y “GSGl ycx II ““1 n
so it is recommended that a new oil pump be scrub the cylinder bore:
installed when rebuilding the engine. thoroughly clean all oft
dry the engine and spra
Completely disassemble the oil pump and thor- with an anti-rust solutio
oughly clean all of the components. Inspect the oil
pro
pump Qears and housing for wear and/or damage. In- exe
sure that the pressure relief valve operates properly sac
and there is no binding or sticking due to varnish or
debris. If all of the parts are in proper working condi-
tion, lubricate the gears and relief valve, and assem-
r
j ht
y the entire assembly down’
in such as WD-4Q@ or similar Fig. 265 Apply a strip of gauging material
Iduct. Take a clean lint-free rag and wipe up any
less anti-rust solution from the bores, bearing
Idles, etc. Repeat the final cleaning process on the !torguethe~~p * ,’ / to the bearmg lournal, then mstall and
ble the pump.
REFINISHING
# See Figure 263
Almost all engine block refinishing must be per-
I
IUIIII~U uy a macnme snap. ir me cynnoers are nor ro
be rebored, then the cylinder glaze can be removed
with a ball hone. When removing cylinder glaze with
a ball hone, use a light or penetrating type oil to Iu-
bricate the hone. Do not allow the hone to run dry as
this may cause excessive scoring of the cylinder
bores and wear on the hone. If new pistons are re-
quired, they will need to be installed to the connect-
ing rods. This should be oerformed bv a machine Fig. 266 After the cap is removed again, use

.
3-68 ENGINEANDENGINEOVERHAUL
crankshaft end-play 8. Install the rear main seal.
the inner portion of the lower land. If the lower
9. After the bearings have been fitted, apply a
lands have high steps, the piston should be re-
light coat of engine oil to the journals and bearings.
placed.
Install the rear main bearing cap. Install all bearing
2. Unless new pistons are installed, be sure to
caps except the thiust bearing cap. Be sure that main
I
install the pistons in the cylinders from which they
bearing caps are installed in original locations.
were removed. The numbers on the connecting rod
Tighten the bearing cap bolts to specifications.
and bearing cap must be on the same side when in-
10. Install the thrust bearing cap with bolts fin-
stalled in the cylinder bore. If a connecting rod is
ger-tight.
ever transposed from one engine or cylinder to an-
11. Pry the crankshaft forward against the thrust
other, new bearings should be fitted and the connect-
surface of upper half of bearing.
ing rod should be numbered to correspond with the *
12. Hold the crankshaft forward and pry the thrust
new cylinder number. The notch on the piston head
bearing cap to the rear. This aligns the thrust sur-
goes toward the front of the engine.
faces of both halves of the bearing.
3. Install all of the rod bearing inserts into the
13. Retain the forward pressure on the crankshaft.
rods and caps.
Tighten the cap bolts to specifications.
4. Install the rings to the pistons. Install the oil
14. Measure the crankshaft end-play as follows:
control ring first, then the second compression ring
a. Mount a dial gauge to the engine block
and finally the top compression ring. Use a piston
and position the tip of the gauge to read from the
ring expander tool to aid in installation and to help
Fig. 266 Carefully pry the crankshafl Ez
and forth while reading the dial gauge for
end-play first rod journal to the bottom of its stroke.
Pistons and Connecting Rods
4. Install the lower main bearing inserts in bear-
ing caps.
5. Clean the mating surfaces of block and rear
main bearing cap.
6. Carefully lower the crankshaft into place. Be
careful not to damage bearing surfaces.
7. Check the clearance of each main bearing by
using the following procedure:
a. Place a piece of Plastigage@ or its equiva-
lent, on bearing surface across full width of bear-
ing cap and about V4 in. off center.
b. Install cap and tighten bolts to specifica-
tions. Do not turn crankshaft while Plastigage@ is
in place.
c. Remove the cap. Using the supplied Plasti-
gage@ scale, check width of Plastigage@ at
widest point to get maximum clearance. Differ-
ence between readings is taper of journal.
d. If clearance exceeds specified limits, try a
0.001 in. or 0.002 in. undersize bearing in com-
bination with the standard bearing. Bearing clear-
ante must be within specified limits. If standard
and 0.002 in. undersize bearing does not bring
clearance within desired limits, refinish crank-
shaft journal, then install undersize bearings. crankshaft end.
b. Carefully pry the crankshaft toward the rear
of the engine and hold it there while you zero the
gauge.
c. Carefully pry the crankshaft toward the
front of the engine and read the gauge.
d. Confirm that the reading is within specifi-
cations. If not, install a new thrust bearing and
repeat the procedure. If the reading is still out of
specifications with a new bearing, have a ma-
chine shop inspect the thrust surfaces of the
crankshaft, and if possible, repair it.
15. Rotate the crankshaft so as to position the
# See Figures 269, 270,271, and 272
1. Before installing the piston/connecting rod
assembly, oil the pistons, piston rings and the cylin-
der walls with light engine oil. Install connecting rod
bolt protectors or rubber hose onto the connecting
rod bolts/studs. Also perform the following:
a. Select the proper ring set for the size cylin-
der bore.
b. Position the ring in the bore in which it is
going to be used.
c. Push the ring down into the bore area
where normal ring wear is not encountered.
d. Use the head of the piston to position the
ring in the bore so that the ring is square with
the cylinder wall. Use caution to avoid damage to
the ring or cylinder bore.
e. Measure the gap between the ends of the
ring with a feeler gauge. Ring gap in a worn
cylinder is normally greater than specification. If
the ring gap is greater than the specified limits,
try an oversize ring set.
f. Check the ring side clearance of the com-
pression rings with a feeler gauge inserted be-
tween the ring and its lower land according to
specification. The gauge should slide freely
around the entire ring circumference without
binding. Any wear that occurs will form a step at reduce the chance of breakage.
5. Make sure the ring gaps are properly spaced
around the circumference of the piston. Fit a piston
ring compressor around the piston and slide the pis-
ton and connecting rod assembly down into the
cylinder bore, pushing it in with the wooden hammer
handle. Push the piston down until it is only slightly
below the top of the cylinder bore. Guide the con-
netting rod onto the crankshaft bearing journal care-
fully, to avoid damaging the crankshaft.
6. Check the bearing clearance of all the rod
bearings, fitting them to the crankshaft bearing jour-
nals. Follow the procedure in the crankshaft installa-
tion above.
7. After the bearings have been fitted, apply a
light coating of assembly oil to the journals and bear-
ings.
8. Turn the crankshaft until the appropriate
bearing journal is at the bottom of its stroke, then
push the piston assembly all the way down until the
connecting rod bearing seats on the crankshaft jour-
nal. Be careful not to allow the bearing cap screws to
strike the crankshaft bearing journals and damage
them.
9. After the piston and connecting rod assem-
blies have been installed, check the connecting rod
side clearance on each crankshaft journal.
10. Prime and install the oil pump and the oil
pump intake tube.
11. Install the auxiliary/balance shaft(s)/assem-
bly(ies).
Cylinder Head(S)
1. Install the cylinder head(s) using new gaskets.
2, Install the timing sprockets/gears and the
belt/chain assemblies.
Engine Covers and Components
Install the timing cover(s) and oil pan. Refer to
your notes and drawings made prior to disassembly
and install all of the components that were removed.
Install the engine into the vehicle.

4-2 DRIVEABILITYAND EMISSIONS CONTROLS
OPERATION
p See Figures 1, 2, and 3
All engines are equipped with the Positive
Crankcase Venhlation (PCV) system. The PCV sys-
tem vents crankcase gases into the engine air intake
where they are burned with the fuel and air mrxture.
The PCV system keeps pollutants from being re-
leased into the atmosphere It also helps to keep the
engine 011 clean, by ridding the crankcase of moisture
and corrosive fumes. The PCV system consists of the
PCV valve, the nipple in the air intake and the con-
necting hoses.
Incorrect operation of the PCV system can cause
multiple driveability symptoms.
A plugged valve or hose may cause’
l Rough Idle l Stalling or slow idle speed l Oil leaks
tT9574goi Fig. 1 Typical PCV system airflow
89574g0r5 Fig. 3 . . .
or mounted in a grommet on the
valve cover
l Sludge in en ine
A leakrng valve or ose would cause: i?
l Rough idle l Stalling l High idle speed
p See Figures 4 and 5
1. Disconnect the ventilation hose from the PCV
valve. Remove the PCV valve from the engine Once
removed, reconnect the ventilation hose to the valve.
2. Start the engine and allow to idle. Place a fin-
ger over open end of the PCV valve. Make sure intake
manifold vacuum is felt on finger.
3. If vacuum is not felt, the PCV valve may be re-
stricted.
4. Turn the engine
OFF and remove the PCV
valve from the hose.
5. Insert a thin stick into the threaded end of the
PCV valve. Push on the inner plunger and inspect for
movement.
6. If plunger inside the PCV valve is not free to
move back and forth, the valve is clogged and WIII re-
quire replacement.
*It is possible to clean the valve using the
appropriate solvent, but replacement is rec-
ommended.
REMOVAL&INSTALLATION
For PCV valve removal and installation, please re-
fer to Section 1 of this manual.
89574QO’ Fig. 4 With the engine idling, check the end
of the PCV valve to see if vacuum is present
Positive crankcase
ventilation
89574go6 Fig. 5 Inspect the PCV valve for inner
plunger movement. If the plunger is bound
or sticking, replace the valve OPERATION
p See Figures 6 and 7
Changes in atmospheric temperature cause fuel
tanks to breathe, that is, the air within the tank ex-
pands and contracts with outside temperature
changes. If an unsealed system was used, when the
temperature rises, air would escape through the tank
vent tube or the vent in the tank cap. The air which
escapes contains gasoline vapors.
The Evaporative Emission Control System pro-
vides a sealed fuel system with the capability to store
and condense fuel vapors. When the fuel evaporates
in the fuel tank, the vapor passes through the EVAP
emission valve, through vent hoses or tubes to a car-
bon filled evaporative canister. When the engine is
operahng the vapors are drawn into the intake mani-
fold and burned during combustion.
A sealed, maintenance free evaporative canister is
used The canister is filled wrth granules of an acti-
vated carbon mixture. Fuel vapors entering the canis-
ter are absorbed by the charcoal granules. A vent cap
is located on the top of the canister to provide fresh
air to the canister when it is being purged. The vent
cap opens to provide fresh air into the canister, which
circulates through the charcoal, releasing trapped va-
pors and carrying them to the engine to be burned.
Fuel tank pressure vents fuel vapors into the can-
ister. They are held in the canister until they can be
drawn into the intake manifold. The canister purge
valve allows the canister to be purged at a pre-deter-
mined time and engine operating conditions.
Vacuum to the canister is controlled by the canis-
ter purge valve. The valve IS operated by the PCM.
The PCM regulates the valve by switching the ground
circuit on and off based on engine operating condi-
tions When energized, the valve prevents vacuum
from reaching the canister. When not energized the
valve allows vacuum to purge the vapors from the
canister.
During warm up and for a specified time after hot
starts, the PCM energizes (grounds) the valve pre-
venting vacuum from reaching the canrster. When the
engine temperature reaches the operating level of
about 120°F (49°C) the PCM removes the ground
from the valve allowing vacuum to flow through the
canister and purges vapors through the throttle body.
During certain Idle conditions, the purge valve may
be grounded to control fuel mixture calibrations.
The fuel tank is sealed with a pressure-vacuum re-
lief filler cap. The relief valve in the cap is a safety
feature, preventing excessive pressure or vacuum in
the fuel tank. If the cap is malfunctioning, and needs
to be replaced, ensure that the replacement is the
identical cap to ensure correct system operation,
OBD-II EVAP System Monitor
Some models have added system components
due to the EVAP system monitor incorporated in the
OBD-II engrne control system. A pressure sensor is
mounted on the fuel tank which measures pressure
inside the tank, and a purge flow sensor measures
the flow of the gases from the canister into the en-
gine.
The PCM can store trouble codes for EVAP sys-
tem performance, a list of the codes is provided later

.
4-18 DRIVEABILITYAND EMISSIONS CONTROLS
Name ; Symbol Name j Symbol
I
Arr conditioning compressor clutch relay ; N Heated oxygen sensor (Rear)
j ”
Air condrtioning swatch , s 1 Idle air control motor
/ F
/
Check engrne/Malfunction Indicator lamp
/ Q lgnrtion trmrng adjustment connector
j D
Crankshaft position sensor / M Injector
! O
Data link connector
j p Intake air temperature sensor / K
Distributor (wrth bulk-in camshaft position sensor, , B Manifold absolute pressure sensor
ignition coil and rgnrtron power transistor) I 1 H
Multrport fuel in]ectron (MFI) relay
i T
EGR solenord
i J PaWNeutral positron switch j A
Engine control module
I u I Power steering pressure switch
Engine coolant temperature sensor c / Throttle position sensor
Evaporative emission purge solenoid
I I I (with burl&In closed throttle position switch) / L _
/ G
I
I
- Fuel pump check terminal /
I j E i Vehicle speed sensor (reed switch)
/ R
Heated oxygen sensor (Front)
I w I
i -
Ilectronic engine control component locations-l 51 engine 93154go1

4-20 , DRIVEABILITYAND EMISSIONS CONTROLS
Name Symbol Name Symbol
Air conditioning compressor clutch relay J Ignition coil (ignition power transistor) F
Air conditlonrng switch 0 Ignition trming adjustment terminal R
Crankshaft positron sensor and camshaft posi- Injector I
tion sensor G
~ Multiport fuel injection relay N
Data link connector s ’
- Oxygen sensor A
EGR solenoid K
~ Park/neutral positron switch M
EGR temperature sensor L
_ Power steering pressure switch
U
Engine control module Q
~ Throttle position sensor
D
Engrne coolant temperature sensor E
Vehicle speed sensor (reed switch) P
Evaporative emrsslon purge solenoid H -
Volume air flow sensor (incorporating intake
Fuel pump check terminal T arr temperature sensor and barometric pres- B
- sure sensor)
Idle speed control motor (closed throttle POW
tron swatch, tdle speed control motor positron
sensor)
! c
93154go: Electronic engine control component locations-2.01 SOHC engine

.
4-24 DRIVEABILITYAND EMISSIONS CONTROLS
Name
Air conditioning compressor clutch relay
Air conditioner switch
Camshaft position sensor
Check engine/malfunction indicator lamp
Crankshaft position sensor
Data link connector
EGR solenoid
Engine control module
Engine coolant temperature sensor
Evaporative emission purge solenoid
Fuel pump check terminal
Heated oxygen sensor (Front) Symbol 1 Name
Symbol
L 1 Heated oxygen sensor (Rear)
C
T / Idle arr control motor
H
I ignition coil (Ignition power transistor)
R
S Injector
N
M Manifold differential pressure sensor
F
U Multiport fuel injection (MFI) relay/Fuel pump V
relay
E Park/Neutral position switch
Q,
W Power steering pressure switch
A
0 Throttle position sensor (with built-in closed
G
throttle position switch)
D Vehicle speed sensor
P
J Volume air flow sensor (with built-in intake air
temperature sensor and barometric pressure
B K
sensor)
ilectronic engine control component locations-3.51 engine