Fig. 18: Measuring Connecting Rod Side Clearance - Typical
This Graphic For General Information Only
Check for improper bearing installation, wrong bearing cap
or insufficient bearing clearance if side clearance is insufficient.
Connecting rod may require machining to obtain proper clearance.
Excessive clearance usually indicates excessive wear at crankshaft.
Crankshaft must be repaired or replaced.
MAIN & CONNECTING ROD BEARING CLEARANCE
Plastigage Method
Plastigage method may be used to determine bearing clearance.
Plastigage can be used with an engine in service or during reassembly.
Plastigage material is oil soluble.
Ensure journals and bearings are free of oil or solvent.
Oil or solvent will dissolve material and false reading will be
obtained. Install small piece of Plastigage along full length of
bearing journal. Install bearing cap in original location. Tighten
bolts to specification.
CAUTION: DO NOT rotate crankshaft while Plastigage is installed.
Bearing clearance will not be obtained if crankshaft is
rotated.
Remove bearing cap. Compare Plastigage width with scale on
Plastigage container to determine bearing clearance. See Fig. 19.
Rotate crankshaft 90 degrees. Repeat procedure. this is done to check
journal eccentricity. This procedure can be used to check oil
clearance on both connecting rod and main bearings.
CYLINDER BLOCK
* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
BLOCK CLEANING
Only cast cylinder blocks should be hot tank cleaned.
Aluminum cylinder blocks should be cleaned using cold tank method.
Cylinder block is cleaned in order to remove carbon deposits, gasket
residue and water jacket scale. Remove oil galley plugs, freeze plugs
and cam bearings prior to block cleaning.
BLOCK INSPECTION
Visually inspect the block. Check suspected areas for cracks
using the Dye Penetrant inspection method. Block may be checked for
cracks using the Magnaflux method.
Cracks are most commonly found at the bottom of the
cylinders, the main bearing saddles, near expansion plugs and between
the cylinders and water jackets. Inspect lifter bores for damage.
Inspect all head bolt holes for damaged threads. Threads should be
cleaned using tap to ensure proper head bolt torque. Consult machine
shop concerning possible welding and machining (if required).
CYLINDER BORE INSPECTION
Inspect the bore for scuffing or roughness. Cylinder bore
is dimensionally checked for out-of-round and taper using dial bore
gauge. For determining out-of-round, measure cylinder parallel and
perpendicular to the block centerline. Difference in the 2 readings
is the bore out-of-round. Cylinder bore must be checked at top, middle
and bottom of piston travel area.
Bore taper is obtained by measuring bore at the top and
bottom. If wear has exceeded allowable limits, block must be honed
or bored to next available oversize piston dimension.
CYLINDER HONING
Cylinder must be properly honed to allow new piston rings to
properly seat. Cross-hatching at correct angle and depth is critical
to lubrication of cylinder walls and pistons.
A flexible drive hone and power drill are commonly used.
Drive hone must be lubricated during operation. Mix equal parts of
kerosene and SAE 20w engine oil for lubrication.
Apply lubrication to cylinder wall. Operate cylinder hone
from top to bottom of cylinder using even strokes to produce 45 degree
cross-hatch pattern on the cylinder wall. DO NOT allow cylinder hone
to extend below cylinder during operation.
Recheck bore dimension after final honing. Wash cylinder
wall with hot soapy water to remove abrasive particles. Blow dry with
compressed air. Coat cleaned cylinder walls with lubricating oil.
DECK WARPAGE
Check deck for damage or warped head sealing surface. Place
a straightedge across gasket surface of the deck. Using feeler gauge,
measure clearance at center of straightedge. Measure across width and
SAE J2210 specifications. If accidental system discharge
occurs, ventilate work area before resuming service.
WARNING: R-134a service equipment or vehicle A/C systems SHOULD NOT
be pressure tested or leak tested with compressed air. Some
mixtures of air/R134a have shown to be combustible at
elevated pressures. These mixtures are dangerous and may
cause fire and/or explosions. See AIR CONDITIONING SERVICE
article in GENERAL INFORMATION section.
AIR CLEANER FILTER
WARNING: Operating the engine with the air cleaner off can cause you
or others to be burned. The air cleaner not only cleans the
air, it stops flame if the engine backfires. Do not drive
with it off, and be careful working on the engine with the
air cleaner off.
ANTI-LOCK BRAKE SYSTEM
The anti-lock brake system contains electronic equipment that
can be susceptible to interference caused by improperly installed or
high output radio transmitting equipment. Since this interference
could cause the possible loss of the anti-lock braking capability,
such equipment should be installed by qualified professionals.
On models equipped with anti-lock brake systems, ALWAYS
observe the following cautions:
* DO NOT attempt to bleed hydraulic system without first
referring to the appropriate ANTI-LOCK BRAKE SYSTEM article
in the BRAKES Section.
* DO NOT mix tire sizes. As long as tires remain close to the
original diameter, increasing the width is acceptable.
Rolling diameter must be identical for all 4 tires. Some
manufacturers recommend tires of the same brand, style and
type. Failure to follow this precaution may cause inaccurate
wheel speed readings.
* Use ONLY recommended brake fluids. DO NOT use silicone brake
fluids in an ABS-equipped vehicle.
AUTOMATIC TRANSAXLE SERVICE
WARNING: Make certain that no fluid is spilled when the transaxle
fluid is inspected, or when fluid is added soon after
driving (since the engine is hot). If the fluid spills onto
the exhaust manifold, there is danger of fire.
BATTERY SERVICE
WARNING: When battery is disconnected, vehicles equipped with
computers may lose memory data. When battery power is
restored, driveability problems may exist on some vehicles.
These vehicles may require a relearn procedure. See COMPUTER
RELEARN PROCEDURES article in GENERAL INFORMATION section.
WARNING: Batteries produce flammable hydrogen gas. Keep flames and
sparks away from the battery or and explosion may occur.
Never smoke when working in the vicinity of the battery.
WARNING: When checking or servicing the battery, disconnect the
negative cable. Be careful not to cause a short circuit by
Loose ................... B ... Require repair or replacement
of affected component.
Lug nut installed
backward ............... B .. Require repair or replacement.
Lug nut mating type
incorrect .............. B ..... Require replacement of nut.
Lug nut mating surface
dished ................. A ..... Require replacement of nut.
Lug nut rounded ......... A . (2) Require replacement of nut.
Lug nut seized .......... A . ( 2) Require replacement of nut.
Stud incorrect .......... B .... Require replacement of stud.
Threads damaged ......... A ... Require repair or replacement
of component with damaged
threads.
Threads stripped ........ A .......... Require replacement of
component with stripped
threads.
( 1) - Some manufacturers require replacement of all studs on
that wheel if two or more studs or nuts on the same
wheel are broken or missing.
( 2) - Only required if removing wheel.
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WHEELS (RIMS)
WARNING: Mounting a regular tire on a high-pressure compact spare
wheel is not permitted. Attempting to mount a tire of one
diameter on a wheel of a different diameter or flange
type may result in serious injury or death. If the wheel
identification stamp is not legible, or cannot be found,
do not use the wheel until the size and type have been
properly identified. Wheels of different diameter,
offset, or width cannot be mixed on the same axle. Bead
seat tapers cannot be interchanged.
WHEEL (RIM) INSPECTION
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Condition Code Procedure
Bead leaking, caused
by wheel ............... A ........... ( 1) Require repair or
replacement.
Bent hub mounting
surface ................ A ............ Require replacement.
Bent rim, causing
vibration .............. 2 ........ ( 1) Suggest replacement.
Broken .................. A ............ Require replacement.
Cast wheel porous,
causing a leak ......... A .. Require repair or replacement.
Clip-on balance weight is
incorrect type
for rim flange ......... 2 ............ Suggest replacement.
Corrosion, affecting
structural integrity ... A ............ Require replacement.
Corrosion build-up on
wheel mounting
surface ................ A ................. Require repair.
Cracked ................. A ............ Require replacement.
Directional/asymmetrical
wheels mounted
incorrectly ............ B ....... Require remounting and/or
repositioning.
Loose ................... B ... Require repair or replacement
of affected component.
Lug nut installed
backward ............... B .. Require repair or replacement.
Lug nut mating type
incorrect .............. B ..... Require replacement of nut.
Lug nut mating surface
dished ................. A ..... Require replacement of nut.
Lug nut rounded ......... A . (2) Require replacement of nut.
Lug nut seized .......... A . ( 2) Require replacement of nut.
Stud incorrect .......... B .... Require replacement of stud.
Threads damaged ......... A ... Require repair or replacement
of component with damaged
threads.
Threads stripped ........ A .......... Require replacement of
component with stripped
threads.
( 1) - Some manufacturers require replacement of all studs on
that wheel if two or more studs or nuts on the same
wheel are broken or missing.
( 2) - Only required if removing wheel.
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WHEELS (RIMS)
WARNING: Mounting a regular tire on a high-pressure compact spare
wheel is not permitted. Attempting to mount a tire of one
diameter on a wheel of a different diameter or flange
type may result in serious injury or death. If the wheel
identification stamp is not legible, or cannot be found,
do not use the wheel until the size and type have been
properly identified. Wheels of different diameter,
offset, or width cannot be mixed on the same axle. Bead
seat tapers cannot be interchanged.
WHEEL (RIM) INSPECTION
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Condition Code Procedure
Bead leaking, caused
by wheel ............... A ........... ( 1) Require repair or
replacement.
Bent hub mounting
surface ................ A ............ Require replacement.
Bent rim, causing
vibration .............. 2 ........ ( 1) Suggest replacement.
Broken .................. A ............ Require replacement.
Cast wheel porous,
causing a leak ......... A .. Require repair or replacement.
Clip-on balance weight is
incorrect type
for rim flange ......... 2 ............ Suggest replacement.
Corrosion, affecting
structural integrity ... A ............ Require replacement.
Corrosion build-up on
wheel mounting
surface ................ A ................. Require repair.
Cracked ................. A ............ Require replacement.
Directional/asymmetrical
wheels mounted
incorrectly ............ B ....... Require remounting and/or
repositioning.
Missing valve lock Install new valve lock
Excessively worn camshaft Replace camshaft, See
lobes ENGINES
Plugged valve lifter oil Eliminate restriction
holes or replace lifter
Faulty valve lifter check Replace lifter check
ball ball, See ENGINES
Rocker arm nut installed Remove and reinstall
upside down correctly
Valve lifter incorrect for Remove and replace
engine valve lifters
Faulty push rod seat or Replace plunger or push
lifter plunger rod
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Noisy Valves Improper valve lash Re-adjust valve lash,
See ENGINES
Worn or dirty valve lifters Clean and/or replace
lifters
Worn valve guides Replace valve guides,
See ENGINES
Excessive valve seat or Reface seats or valve
face run-out face
Worn camshaft lobes Replace camshaft, See
ENGINES
Loose rocker arm studs Re-tighten rocker arm
studs, See ENGINES
Bent push rods Replace push rods, See
ENGINES
Broken valve springs Replace valve springs,
See ENGINES
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Burned,Sticking Weak valve springs or Replace valves and/or
or Broken Valves warped valves springs, See ENGINES
Improper lifter clearance Re-adjust clearance or
replace lifters
Worn guides or improper Replace valve guides,
guide clearance See ENGINES
Out-of-round valve seats Re-grind valve seats
or improper seat width
Gum deposits on valve Remove deposits
stems, seats or guides
Improper spark timing Re-adjust spark timing
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Broken Undersize pistons Replace with larger
Pistons/Rings pistons, See ENGINES
Wrong piston rings Replace with correct
rings, See ENGINES
Out-of-round cylinder bore Re-bore cylinder bore
Improper connecting rod Remove and realign
alignment connecting rods
Excessively worn ring Replace pistons, See
grooves ENGINES
Improperly assembled Re-assemble pin-to
piston pins -piston, See ENGINES
Insufficient ring gap Install new rings, See
clearance ENGINES
Engine overheating Check cooling system
Incorrect ignition timing Re-adjust ignition
timing, See TUNE-UP
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Excessive Leaks at manifold to Replace manifold or
Exhaust Noise head, or to pipe pipe gasket
Exhaust manifold Replace exhaust
The noid light is an excellent "quick and dirty" tool. It can
usually be hooked to a fuel injector harness fast and the flashing
light is easy to understand. It is a dependable way to identify a no-
pulse situation.
However, a noid light can be very deceptive in two cases:
* If the wrong one is used for the circuit being tested.
Beware: Just because a connector on a noid light fits the
harness does not mean it is the right one.
* If an injector driver is weak or a minor voltage drop is
present.
Use the Right Noid Light
In the following text we will look at what can happen if the
wrong noid light is used, why there are different types of noid lights
(besides differences with connectors), how to identify the types of
noid lights, and how to know the right type to use.
First, let's discuss what can happen if the incorrect type of
noid light is used. You might see:
* A dimly flashing light when it should be normal.
* A normal flashing light when it should be dim.
A noid light will flash dim if used on a lower voltage
circuit than it was designed for. A normally operating circuit would
appear underpowered, which could be misinterpreted as the cause of a
fuel starvation problem.
Here are the two circuit types that could cause this problem:
* Circuits with external injector resistors. Used predominately
on some Asian & European systems, they are used to reduce the
available voltage to an injector in order to limit the
current flow. This lower voltage can cause a dim flash on a
noid light designed for full voltage.
* Circuits with current controlled injector drivers (e.g. "Peak
and Hold"). Basically, this type of driver allows a quick
burst of voltage/current to flow and then throttles it back
significantly for the remainder of the pulse width duration.
If a noid light was designed for the other type of driver
(voltage controlled, e.g. "Saturated"), it will appear dim
because it is expecting full voltage/current to flow for the
entire duration of the pulse width.
Let's move to the other situation where a noid light flashes
normally when it should be dim. This could occur if a more sensitive
noid light is used on a higher voltage/amperage circuit that was
weakened enough to cause problems (but not outright broken). A circuit\
with an actual problem would thus appear normal.
Let's look at why. A noid light does not come close to
consuming as much amperage as an injector solenoid. If there is a
partial driver failure or a minor voltage drop in the injector
circuit, there can be adequate amperage to fully operate the noid
light BUT NOT ENOUGH TO OPERATE THE INJECTOR.
If this is not clear, picture a battery with a lot of
corrosion on the terminals. Say there is enough corrosion that the
starter motor will not operate; it only clicks. Now imagine turning on
the headlights (with the ignition in the RUN position). You find they
light normally and are fully bright. This is the same idea as noid
light: There is a problem, but enough amp flow exists to operate the
headlights ("noid light"), but not the starter motor ("injector").
How do you identify and avoid all these situations? By using
the correct type of noid light. This requires that you understanding
full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturer's systems.
The second method is to use a lab scope. Remember, a lab
scope allows you to see the regular operation of a circuit in real
time. If an injector is having an short or intermittent short, the lab
scope will show it.
Checking Available Voltage At the Injector
Verifying a fuel injector has the proper voltage to operate
correctly is good diagnostic technique. Finding an open circuit on the
feed circuit like a broken wire or connector is an accurate check with
a DVOM. Unfortunately, finding an intermittent or excessive resistance
problem with a DVOM is unreliable.
Let's explore this drawback. Remember that a voltage drop due
to excessive resistance will only occur when a circuit is operating?
Since the injector circuit is only operating for a few milliseconds at
a time, a DVOM will only see a potential fault for a few milliseconds.
The remaining 90+% of the time the unloaded injector circuit will show
normal battery voltage.
Since DVOMs update their display roughly two to five times a
second, all measurements in between are averaged. Because a potential
voltage drop is visible for such a small amount of time, it gets
"averaged out", causing you to miss it.
Only a DVOM that has a "min-max" function that checks EVERY
MILLISECOND will catch this fault consistently (if used in that mode).\
The Fluke 87 among others has this capability.
A "min-max" DVOM with a lower frequency of checking (100
millisecond) can miss the fault because it will probably check when
the injector is not on. This is especially true with current
controlled driver circuits. The Fluke 88, among others fall into this
category.
Outside of using a Fluke 87 (or equivalent) in the 1 mS "min-\
max" mode, the only way to catch a voltage drop fault is with a lab
scope. You will be able to see a voltage drop as it happens.
One final note. It is important to be aware that an injector
circuit with a solenoid resistor will always show a voltage drop when
the circuit is energized. This is somewhat obvious and normal; it is a
designed-in voltage drop. What can be unexpected is what we already
covered--a voltage drop disappears when the circuit is unloaded. The
unloaded injector circuit will show normal battery voltage at the
injector. Remember this and do not get confused.
Checking Injector On-Time With Built-In Function
Several DVOMs have a feature that allows them to measure
injector on-time (mS pulse width). While they are accurate and fast to\
hookup, they have three limitations you should be aware of:
* They only work on voltage controlled injector drivers (e.g
"Saturated Switch"), NOT on current controlled injector
drivers (e.g. "Peak & Hold").
* A few unusual conditions can cause inaccurate readings.
* Varying engine speeds can result in inaccurate readings.
Regarding the first limitation, DVOMs need a well-defined
injector pulse in order to determine when the injector turns ON and
OFF. Voltage controlled drivers provide this because of their simple
switch-like operation. They completely close the circuit for the
entire duration of the pulse. This is easy for the DVOM to interpret.
The other type of driver, the current controlled type, start
off well by completely closing the circuit (until the injector pintle
opens), but then they throttle back the voltage/current for the
duration of the pulse. The DVOM understands the beginning of the pulse