light MITSUBISHI DIAMANTE 1900 Manual PDF

FUELSYSTEM 5-7
Fig, 25 Remove the vacuum hose from the Fig. 25 Detach the connectors from all of
pressure regulator the fuel injectors
1 H; :A ..;lt;;aft~rgi,i~;yl the ;F: 1 / . 93155p15 1 Fig 29 Remove the fuel injectors from the
tall by gently rocking them loose Fig. 27 Remove the two fuel rail retaining
bolts . . .
93155ps Fig. 30 Always replace the O-rings on the
injectors before reinstalling them
1. Relieve the fuel system pressure as described
in this section.
2. Label and disconnect the spark plug wires. ’
Position the wires aside.
3. Disconnect the PCV hose from the valve
cover,
4. Remove the bolts holding the high pressure
fuel line to the fuel rail, then disconnect the line. Be
prepared to contain fuel spillage; plug the line to on the workbench; protect the tips of the injectors
from dirt and/or impact.
9. Remove and discard the injector insulators
from the intake manifold. The insulators are not
reusable.
10. Remove the injectors from
pulling gently in a straight outwarc the fuel rail by
I motion. Make cer-
tain the grommet and O-ring come off with the injector. 18. Connect the fuel return hose to the pressure
regulator, then connect the vacuum hose.
19. Replace the O-ring on the high pressure fuel
line, coat the O-ring lightly with clean, thin oil and
install the line to the fuel rail. Tiahten the mountina
To install: -
the fuel system and inspect all connections for leaks. bolts to 4 ft. Ibs. (6 Nm).
20. Connect the PCV hose and spark plug wires.
21. Connect the negative battery cable. Pressurize
1. neneve me rueI system pressure.
2. Disconnect the negative battery cable. 3.OL and 3.5L Engines
# See Figures 31 and 32
> - ,. .* , ,
I
I
Work MUST NOT be started until at least 90
seconds after the ignition switch is turned to
the LOCK position and the negative battery
cable is disconnected from the battery. This
will allow time for the air bag system backup
power supply to deplete its stored energy,
preventing accidental air bag deployment
which could result in unnecessary air bag
system repairs and/or personal injury.
3. Drain the cooling system.
4. Disconnect all components from the air in-
take plenum and remove the plenum from the intake
manifold. Refer to Section 3.
5. Wrap the connection with a shop towel and
disconnect the high pressure fuel line at the fuel rail. keep out dirt and debris.
Observe all applicable safety precautions
when working around fuel. Whenever servic-
ing the fuel system, always work in a well
ventilated area. Do not allow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extin-
guisher near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel con-
tainers to avoid the possfbility of fire or ex-
plosion.
5. Remove the vacuum hose from the fuel pres-
sure regulator.
6. Disconnect the fuel return hose from the
pressure regulator.
7. Label and detach the electrical connectors
from each injector.
8. Remove the bolt(s) holding the fuel rail to the
manifold. Carefully lift the rail up and remove it with
the injectors attached. Take great care not to drop an
injector. Place the rail and injectors in a safe location 11. Install a new insulator in each injector port in
the manifold.
12. Remove the old grommet and D-ring from
each injector. Install a new grommet and O-ring; coat
the O-ring lightly with clean, thin oil.
13. If the fuel pressure regulator was removed, re-
place the O-ring with a new one and coat it lightly with
clean, thin oil. Insert the regulator straight into the rail,
then check that it can be rotated freely. If it does not ro-
tate smoothly, remove it and inspect the O-ring for de-
formation or jamming. When properly installed, align
the mounting holes and tighten the retaining bolts to 7
ft. Ibs. (9 Nm). This procedure must be followed even if
the fuel rail was not removed.
14. Install the injector into the fuel rail, constantly
turning the injector left and right during installation.
When fully installed, the injector should still turn
freely in the rail. If it does not, remove the injector
and inspect the O-ring for deformation or damage.
15. Install the delivery pipe and injectors to the
engine. Make certain that each injector fits correctly
into its port and that the rubber insulators for the fuel
rail mounts are in position.
16. Install the fuel rail retaining bolts and tighten
them to 9 ff. Ibs. (12 Nm).
17. Connect the wiring harnesses to the appro-
priate injector.

5-8 FUELSYSTEM
9 ,npimr w1m.m
1: i”“L,
1: 82”w
93155gx Fig. 31 Exploded view of the fuel injectors and related components-
s.OL engines
Observe all applicable safety precautions
when working around fuel. Whenever servic-
ing the fuel system, always work in a well
ventilated area. Do not allow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extin-
guisher near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel con-
tainers to avoid the possibility of fire or ex-
plosion.
6. Disconnect the fuel return hose and remove
the O-ring.
7. Disconnect the vacuum hose from the fuel
pressure regulator.
8. Detach the electrical connectors from each
injector.
9. Remove the fuel pipe connectmg the fuel
rails. Remove the injector rail retaining bolts. Make
sure the rubber mounting bushings do not get lost.
10. Lift the rail assemblies up and away from the
engine.
11. Remove the injectors from the rail by pulling
gently. Discard the lower insulator.
To install:
*Some of the vehicles may have a clip that
secures the injector to the fuel rail. Be sure
to remove or install the injector clip where
necessary.
12. Install a new grommet and O-ring to the in-
jector. Coat the O-ring with light oil.
13. Install the injector to the fuel rail.
14. Replace the seats in the intake manifold. In-
stall the fuel rails and injectors to the manifold. Make
sure the rubber bushings are in place before tighten-
ing the mounting bolts.
15. Tighten the retaining bolts to 7-9 ft. Ibs.
(W-13 Nm) Install the fuel pipe with new gasket.
16. Attach the electrical connectors to the injec-
tors
Fig. 32 Exploded view of the fuel injectors and related components-
3.5L engine
17. Connect the fuel return hose.
18. Replace the O-ring, lightly lubricate it and
connect the high pressure fuel line.
19. Usmg new gaskets, install the intake plenum
and all related items. Refer to Section 3.
20. Fill the cooling system.
21. Connect the negative battery cable and check
the entire system for proper operation and leaks.
The easiest way to test the operation of the fuel in-
jectors is to listen for a clicking sound coming from
the injectors while the engine IS running. This is ac-
complished using a mechanic’s stethoscope, or a
long screwdriver. Place the end of the stethoscope or
the screwdriver (tip end, not handle) onto the body of
the injector. Place the ear pieces of the stethoscope
in your ears, or if using a screwdriver, place your ear
on top of the handle. An audible chcking noise
should be heard; this is the solenoid operating. If the
injector makes this noise, the injector driver circuit
and computer are operating as designed. Continue
testing all the injectors this way.
Be extremely careful while working on an op-
erating engine, make sure you have no dan-
gling jewelry, extremely loose clothes,
power tool cords or other items that might
get caught in a moving part of the ermine.
All Injectors Clicking
If all the injectors are clicking, but you have de-
termined that the fuel system is the cause of your
driveability problem, continue diagnostics. Make
sure that you have checked fuel pump pressure as
outlined earlier in this section. An easy way to de-
termine a weak or unproductive cylinder is a cylin-
der drop test. This is accomplished by removing
one spark plug wire at a time, and seeing which cylinder causes the least difference in the idle.
The one that causes the least change is the weak
cylinder.
If the injectors were all clicking and the ignition
system is functioning properly, remove the injector of
the suspect cylinder and bench test it. This is accom-
plished by checking for a spray pattern from the in-
jector itself Install a fuel supply line to the injector
(or rail if the injector is left attached to the rail) and
momentarily apply 12 volts DC and a ground to the
injector itself; a visible fuel spray should appear. If no
spray is achieved, replace the injector and check the
running condition of the engine.
One or More Injectors Are Not Clicking
6 See Figures 33, 34, 35, and 36
If one or more injectors are found to be not operat-
ing, testing the injector driver circuit and computer
can be accomplished using a “noid” light. First, with
the engine not running and the ignition key in the
OFF position, remove the connector from the injector
you plan to test, then plug the “noid” light tool into
the injector connector. Start the engine and the
“noid” light should flash, signaling that the injector
driver circuit is working. If the “noid” light flashes,
but the injector does not click when plugged in, test
the injectors resistance. Resistance should be be-
tween:
l All non-turbo engines: 13-16 ohms at 68°F
(20°C)
l Turbocharged engines: 2-3 ohms at 68 “F
(20°C)
If the “noid” light does not flash, the injector dri-
ver circuit is faulty. Disconnect the negative battery
cable. Unplug the “noid” light from the injector con-
nector and also unplug the PCM. Check the harness
between the appropriate pins on the harness side of
the PCM connector and the injector connector. Re-
sistance should be less than 5.0 ohms; if not, repair
the circuit. If resistance
IS within specifications, the
injector driver inside the PCM is faulty and replace-
ment of the PCM will be necessary.

FUELSYSTEM 5-9
p See Figures 37, 38, 39, 49, and 41
REMOVAL& INSTALLATION
1. Properly relieve the fuel system pressure as
outlined earlier in this section.
2. Remove the vacuum hose from the fuel pres-
sure regulator.
3. Disconnect the fuel return hose from the
pressure regulator.
Fig. 33 Unplug the fuel injector connector
, Observe all applicable safety precautions
when working around fuel. Whenever servic-
ing the fuel system, always work in a well
ventilated area. Do not apow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extin-
guisher near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel con-
tainers to avoid the possibility of fire or ex-
plosion.
I ,“~“*I.“. ..-.. * . ..” ._“. .-... To install:
I
Fig. 36 If the correct “noid” light flashes
while the engine is running, the injector dri-
ver circuit inside the PCM is working 5. Replace the O-ring on fuel pressure regulator
with a new one and coat it lightly with clean, thin oil.
6. Insert the regulator straight into the rail, then
chl . . . . . * * . . , .
xk mat n can oe rorarea rreery. 4. Remove the fuel regulator retainer bolts or re-
move the retaining snapring, then remove the fuel rrwkdnr frnm the fl~el rail
91055pu2 Fig. 35 Plug the correct “noid” light directly
into the iniector harness connector
I I I , r,
If it does not rotate smoothly, remove it
and inspect the O-ring for deformation or
damage.
7. When properly installed, align the mounting
holes. If equipped, install and tighten the retaining
bolts to 8 ft. Ibs. (11 Nm). If equipped, install the reg-
ulator retaining snapring.
8. Connect the fuel return hose to the pressure
regulator.
9. Install the vacuum hose to the fuel pressure
regulator.
10. Connect the negative battery cable and pres-
surize the fuel system. Inspect for leaks.
1 ret;rnline ~ . . g315sp10 1 1 ~~~.~~~s~~~~~u~s,“p”“““’ the hose? 1 Fig 37 Remove the hose clamp on the fuel
Fig. 39 Remove the vacuum hose from the
pressure regulator Fig. 40 Remove the regulator-to-fuel rail re-
taining bolts, then remove the pressure reg-
ulator from the fuel rail

5-10 FUELSYSTEM
1. _
Fuel tank pressure
-
relef vdive

REMOVAL &INSTALLATION
p See Figures 42 and 43
1. Raise and safely support the vehicle securely
on jackstands.
2. Remove the hoses and remove the pressure re-
lief valve.
3. The installation is the reverse of removal.
c, Always install the pressure relief valve
with the arrow pointing toward the EVAP can-
ister side, not the fuel tank 1 mame shown, others similar g3155g” Fig 42 Pressure relief valve location-llia
I I
Evaporatwe emlsslon
canister side
Tank side
+k
93155gt7 Fig. 43 Always install the pressure relief
valve with the arrow pointing toward the
EVAP canister side, not the fuel tank
REMOVAL&INSTALLATION
p See Figures 44 thru 58
1. Properly relieve the fuel system pressure us-
ing proper procedures.
2. Disconnect the negative battery cable.
3. Raise the vehicle and support safelv.
4. Drain the fuel from the fuel tank into an
ap- proved container.
Observe all applicable safety precautions
when working around fuel. Whenever servic-
ing the fuel system, always work in a well
ventilated area. Do not allow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extin-
guisher near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel con-
tainers to avoid the possibility of fire or ex-
plosion.
5. On Diamante models:
a. Remove the left rear wheel well liner.
b Disconnect the center exhaust system from
the main muffler. Disconnect the rear exhaust
hangers, lower the exhaust and secure aside.
c. On models equipped with 4-wheel steering,
remove the mounting bolts and lower the rear
steering gear.
6. Disconnect the return hose, high pressure
hose and vapor hoses from the fuel pump.
7. Detach the electrical connectors at the
pump/sending unit.
8. Disconnect the filler and vent hoses.
s
9. Place a suitable jack under the center of the
fuel tank and apply a slight upward pressure. Remove
the fuel tank strap retaining nuts.
10. Lower the tank slightly and detach any re-
maining electrical or hose connectors at the fuel tank.
11. Remove the fuel tank from the vehicle.
To install: 12. If replacing the tank, transfer any necessary
components to the new tank including any heat
shields, hoses, valves, and the fuel pump.
13. Install the fuel tank onto the jack. Rarse the
tank in position under the vehicle. Leave enough
Tg. 44 Fuel tank and related components exploded view-1990-92
mirage
clearance to attach the electrical and hose connec-
tions to the top of the fuel pump.
14. Attach all connectrons to the top of the tank.
15. Raise the tank completely and position the re-
tainer straps around the fuel tank. Install new fuel
tank self-locking nuts and tighten the nuts.
16. Connect the return hose and high pressure
hoses.
17. Install the vapor hose and the filler hose. In-
stall the filler hose retainer screws to the fender, if re-
moved.
18. On Diamante models:
a. If equipped with 4-wheel steering, install
the power cylinder unit and tighten the mounting
bolts to 31 ft. Ibs. (43 Nm).
b. Connect the exhaust pipe and secure the
rear hangers.
c. Install the left rear wheel well liner, if re-
moved.
19. Lower the vehicle and pour the drained fuel
into the gas tank.
20. Connect the negative battery cable. Check the
fuel pump for proper pressure and inspect the entire
system for leaks.
:ig. 45
vlirage Fuel tank and related 93155(12E components exploded view-1993-96

FUELSYSTEM 5-11
93155gZi Fig. 46 Fuel tank and related components exploded view-1997-98
Mirage
Vapor hose
Filler
hose
Fig. 48 Connection of the vapor and filler hoses-1990-93 FWD Galanl Qt. 49 Fuel tank and related components-1990-93 FWD Galant
1990-92 Mirage
p See Figure 44
REMOVAL &INSTALLATION
Fuel injection systems remain under pres-
sure after the engine has been turned OFF.
Properly relieve fuel pressure before discon-
necting any fuel lines. Failure to do so may
result in fire or personal iniury.
*Cover all fuel hose connections with a
shop towel, prior to disconnecting, to prevent
splash of fuel that could be caused by resid-
ual pressure remaining in the fuel line. Fig. 47 Fuel tank and related components exploded view-1999-00
1996 moclab>
1. Properly relieve the fuel system pressure us-
ing proper procedures. Disconnect the negative bat-
tery cable
2. Raise the vehicle and support safely.
3.
Dram the fuel from the fuel tank Into an ap-
proved container.
Observe all applicable safety precautions
when working around fuel. Whenever servic-
ing the fuel system, always work in a well
ventilated area. Do not allow fuel spray or
vapors to come in contact with a spark or
open flame. Keep a dry chemical fire extin- guisher near the work area. Always keep fuel
in a container specifically designed for fuel
storage; also, always properly seal fuel con-
tainers to avoid the possibility of fire or ex-
plosion.
4. Lower the tank slightly and detach any re-
maining electrical or hose connectors at the fuel tank.
5. Remove the fuel tank from the vehicle as de-
scribed In this section.
6 Remove the five nuts securing the fuel pump
to the fuel tank and remove the pump assembly.
To install:
7. Install fuel pump into fuel tank, with new
packing gasket, and tighten mounting nuts.
8. Install the fuel tank into the vehrcle. Refer to
the procedure in this section.

FUELSYSTiM 5-13
1. BODY HARNESS CONNECTION
2 HOSE CONNECTION
3 PURGE HOSE
4 VAPOR HOSE
5 VENT HOSE
6 FllLER HOSE
7 PIPE ASSEMBLY
8. BAND ASSEMBLY
9 FUEL TANK ASSEMBLY
10. DIFFERENTIAL PRESSURE
SENSOR
11 FUEL HARNESS
12 HIGH-PRESSURE FUEL HOSE 1; ;;JL RETURN HOSE
15 FUEL PUMP MODULE
16 FILLER NECK
17 FUEL CAP
IS REINFORCEMENT
19 PACKING
20 VAPOR HOSE
21 SEPARATOR ASSEMBLY
22 VAPOR HOSE
23 FUEL CHECK VALVE ASSEMBLY
24 FUEL FILLER NECK ASSEMBLY
Fig. 54 Fuel tank and related components-1999-00 Galant
:ia. 55 Fuel tank and related components-1992-96 Diamante
11. Align the 3 projections on packing with the
holes on the fuel pump and the nipples on the pump
facing the same direction as before removal.
12. Install the holdrng bolt through the bottom of
the tank. Make sure the gasket on the bolt is replaced
and is not pinched during installation. Torque to 10
ft. Ibs. (14 Nm).
1 PatkIng brake cable COnneCtlo” 11
2 Fuel tank “.qm hose
12 Fuel fllk, neck
3 “apot hose 13 Fuel filler assembly
4 Pressure hose 14
5 Vapor hose COnneCflOn Fuel p,pe
6 Fuel pump am gauge assembly
7 Vapor hose
8 Valve assembly
9 Fuel mer cap
10 FllkY hose
:ig. 56 Fuel tank and related components-1997-00 Diamante 93155g15
cal harness of the fuel gauge unit to allow for the fuel
pling. Lower the lateral rod and suspend from the
tank to be lowered slightly. If not, label and discon-
axle beam using wire.
nect the electrical harness at the fuel gauge unit.
6. Detach the high pressure fuel line connector 9. Remove the six retaining bolts and gasket
from the base of the tank.
at the pump.
10. Remove the fuel pump assembly.
7. Loosen self-lockinq nuts on tank suooort
To install: straps to the end of the stud bolts.
8 Remove the right side lateral rod attaching
bolt and drsconnect the arm from the right body cou- *If the packing material is damaged or de-
formed, replace it with new packing.
7923PG79 :ig. 57 Proper method of supporting real
rxhaust system-Diamante 3.01 engine

UNDERSTANDING AND
TROUBLESHOOTING
ELECTRICAL SYSTEMS 6-2
BASIC ELECTRICALTHEORY 6-2
HOW DOES ELECTRICITY WORK:
THEWATERANALOGY 6-2
OHM'S LAW 6-2
ELECTRICALCOMPONENTS 6-2
POWERSOURCE 6-2
GROUND 6-3
PROTECTIVE DEVICES 6-3
SWITCHES&RELAYS 6-3
LOAD 6-3
WIRING & HARNESSES 6-3
CONNECTORS 6-4
TEST EQUIPMENT 6-4
JUMPER WIRES 6-4
TEST LIGHTS 6-4
MULTIMETERS 6-5
TROUBLESHOOTING ELECTRICAL
SYSTEMS 6-5
TESTING 6-5
OPEN CIRCUITS 6-5
SHORT CIRCUITS 6-6
VOLTAGE 6-6
VOLTAGE DROP 6-6
RESISTANCE 6-8
WIRE AND CONNECTORREPAIR 6-6
BATTERY CABLES 6-7
DISCONNECTING THE CABLES 6-7
AIR BAG (SUPPLEMENTAL
RESTRAINT SYSTEM) 6-7
GENERALINFORMATION 6-7
SERVICE PRECAUTIONS 6-7
DISARMING 6-7
REARMING 6-7
HEATING AND AIR
CONDITIONING 6-7
BLOWER MOTOR 6-7
REMOVAL &INSTALLATION 6-7
HEATER CORE 6-9 INSTRUMENTS AND SWITCHES 6-17
INSTRUMENTCLUSTER 6-17
REMOVAL &INSTALLATION 6-17
GAUGES 6-18
REMOVAL&INSTALLATION 6-18
WINDSHIELD WIPER SWITCH 6-19
REMOVAL&INSTALLATION 6-19
REARWINDOWWIPERSWITCH 6-19
REMOVAL &INSTALLATION 6-19
DIMMER SWITCH 6-19
REMOVAL & INSTALLATION 6-19 .
HEADLIGHT SWITCH 6-19
REMOVAL & INSTALLATION 6-19
LIGHTING 6-19
HEADLIGHTS 6-19
REMOVAL &INSTALLATION 6-19
AIMINGTHEHEADLIGHTS 6-20
SIGNAL AND MARKER LIGHTS 6-21
REMOVAL &INSTALLATION 6-21
CIRCUIT PROTECTION 6-27
FUSES 6-27
REPLACEMENT 6-27
FUSIBLE LINKS 6-27
CIRCUIT BREAKERS 6-28
RESETTING AND/OR
REPLACEMENT 6-28
FLASHERS 6-28
REPLACEMENT 6-28
WIRING DIAGRAMS 6-31
REMOVAL & INSTALLATION 6-9
AIR CONDITIONING COMPONENTS 6-11
REMOVAL & INSTALLATION 6-11
CONTROLCABLES 6-12
ADJUSTMENT 6-12
CONTROL PANEL 6-12
REMOVAL & INSTALLATION 6-12
CRUISE CONTROL 6-13
ENTERTAINMENT SYSTEMS 6-14
RADIO RECEIVER/AMPLIFIER/TAPE
PLAYER/CD PLAYER 6-14
SPEAKERS 6-14
REMOVAL & INSTALLATION 6-14
WINDSHIELD WIPERS AND
WASHERS 6-15
WINDSHIELD WIPER BLADE AND
ARM 6-15
REMOVAL & INSTALLATION 6-15
WINDSHIELD WIPER MOTOR 6-16 _
REMOVAL &INSTALLATION 6-16
WINDSHIELD WASHER PUMP 6-17
REMOVAL &INSTALLATION 6-17

6-2 CHASSIS ELECTRICAL
) See Figure 1
For any 12 volt, negative ground, electrical system
to operate, the electricity must travel in a complete
circurt. This simply means that current (power) from
the posibve (t) terminal of the battery must eventu-
ally return to the negative (-) terminal of the battery.
Along the way, this current will travel through wires,
fuses, switches and components. If, for any reason,
the flow of current through the circuit is interrupted,
the component fed by that circuit will cease to func-
tion properly.
Perhaps the easiest way to visualize a circuit is to
think of connecting a light bulb (with two wires at-
tached to it) to the battery-one wire attached to the
negative (-) terminal of the battery and the other wire
to the positive (t) terminal. With the two wires touch-
ing the battery terminals, the circuit would be com-
plete and the light bulb would illummate. Electricity
would follow a path from the battery to the bulb and
back to the battery. It’s easy to see that wrth longer
wires on our light bulb, it could be mounted any-
where. Further, one wire could be fitted with a switch
so that the light could be turned on and off.
The normal automotive circuit differs from this
simple example in two ways, Frrst, instead of having
a return wire from the bulb to the battery, the current
travels through the frame of the vehicle. Since the
negative (-) battery cable is attached to the frame
(made of electrically conductive metal), the frame of
the vehicle can serve as a ground wire to complete
the circuit. Secondly, most automotive circuits con-
tain multiple components which receive power from a
single circuit. This lessens the amount of wire
needed to power components on the vehicle.
HOW DOES ELECTRlClTYWORK:THE
WATER ANALOGY
Electricity is the flow of electrons-the subatomic
particles that constitute the outer shell of an atom.
Electrons spin in an orbit around the center core of
RETURN
RETURN
CONDUCTOR
CONDUCTOR
GROUND
GROUND
lccs2w
Fig. 1 This example illustrates a simple cir-
cuit. When the switch is closed, power from
the positive (t) battery terminal flows
through the fuse and the switch, and then
to the light bulb. The light illuminates and
the circuit is completed through the ground
wire back to the negative (-) battery termi-
nal. In reality, the two ground points shown
in the illustration are attached to the metal
frame of the vehicle, which completes the
circuit back to the battery
an atom The center core is comprised of protons
(positive charge) and neutrons (neutral charge). Elec-
trons have a negative charge and balance
out the
positive charge of the protons. When an outside force
causes the number of electrons to unbalance the
charge of the protons, the electrons will split off the
atom and look for another atom to balance out. If this
imbalance is kept up, electrons will continue to move
and an electrical flow will exist.
Many people have been taught electrical theory
using an analogy with water. In a comparison wrth
water flowing through a pipe, the electrons would be
the water and the wire is the pipe.
The flow of electricity can be measured much like
the flow of water through a pipe. The unit of measure-
ment used is amperes, frequently abbreviated as
amps (a). You can compare amperage to the volume
of water flowing through a pipe. When connected to a
circuit, an ammeter WIII measure the actual amount of
current flowing through the circuit. When relatively
few electrons flow through a circuit, the amperage is
low. When many electrons flow, the amperage is
high.
Water pressure is measured in units such as
pounds per square inch (psi); The electrical pressure
is measured in unrts called volts (v). When a volt-
meter is connected to a circuit, it is measuring the
electrical pressure.
The actual flow of electricity depends not only on
voltage and amperage, but also on the resistance of
the circuit The higher the resistance, the higher the
force necessary to push the current through the cir-
cuit. The standard unit for measuring resistance is an
ohm. Resistance in a crrcuit varies dependmg on the
amount and type of components used in the circuit.
The main factors which determine resistance are:
l Material-some materials have more resis-
tance than others Those with high resistance are said
to be insulators Rubber materials (or rubber-like
plashcs) are some of the most common insulators
used in vehicles as they have a very high resistance
to electricity Very low resistance materials are said to
be conductors. Copper wire is among the best con-
ductors. Silver is actually a superior conductor to
copper and is used in some relay contacts, but its
high cost prohibits its use as common wiring Most
automotive wiring is made of copper.
l Size-the larger the wire size being used, the
less resistance the wire will have. This IS why com-
ponents which use large amounts of electricity usu-
ally have large wires supplying current to them.
l Length-for a given thickness of wire, the
longer the wire, the greater the resistance. The
shorter the wire, the less the resistance. When deter-
mining the proper wire for a circuit, both size and
length must be considered to design a circuit that can
handle the current needs of the component.
l Temperature-with many materials, the higher
the temperature, the greater the resistance (positive
temperature coefficient). Some materials exhibit the
opposite trait of lower resistance with higher temper-
atures (negative temperature coefficient). These prin-
ciples are used in many of the sensors on the engine
OHM'S LAW
There is a direct relationship between current,
voltage and resistance. The relationship between cur- rent, voltage and resistance can be summed up by a
statement known as Ohm’s law.
Voltage (E) is equal to amperage (I) times resis-
tance (R): E=l x R
Other forms of the formula are R=E/I and I=E/R
In each of these formulas, E is the voltage in volts,
I is the current in amps and R IS the resistance in
ohms. The basic point to remember is that as the re-
sistance of a circuit goes up, the amount of current
that flows in the circuit will go down, if voltage re-
mains the same.
The amount of work that the electricity can perform
is expressed as power. The unit of power is the watt
(w). The relationship between power, voltage and
current
IS expressed as:
Power(w) is equal to amperage (I) times voltage
(E): W=l x E
This is only true for direct current (DC) circuits:
The alternating current formula is a tad different, but
since the electrical circuits in most vehicles are DC
type, we need not get into AC circuit theory.
POWERSOURCE
Power is supplied to the vehicle by two devices:
The battery and the alternator. The battery supplies
electrical power during starting or during periods
when the current demand of the vehicle’s electrical
system exceeds the output capacity of the alternator.
The alternator supplies electrical current when the
engine is running
Just not does the alternator supply
the current needs of the vehicle, but it recharges the
battery.
The Battery
In most modern vehicles, the battery is a lead/acid
electrochemical device consisting of six 2 volt sub-
sections (cells) connected in series, so that the unit
is capable of producing approximately 12 volts of
electrical pressure. Each subsection consists of a se-
ries of positive and negative plates held a short dis-
tance apart in a solutron of sulfuric acid and water.
The two types of plates are of dissimilar metals,
This sets up a chemrcal reaction, and it is this reac-
tion which produces current flow from the battery
when Its positive and negattve terminals are con-
nected to an electrical load. The power removed from
the battery is replaced by the alternator, restoring the
battery to its original chemical state.
The Alternator
On some vehicles there isn’t an alternator, but a
generator. The difference IS that an alternator sup-
plies alternating current which is then changed to di-
rect current for
use on the vehicle, while a generator
produces direct current. Alternators tend to be more
efficient and that is why they are used.
Alternators and generators are devices that consist
of coils of wires wound together making big electro-
magnets. One group of coils spins within another set
and the interaction of the magnetic fields causes a
current to flow. This current is then drawn off the
coils and fed into the vehicles electrical system.

I
6-4 CHASSIS ELECTRICAL
I
printed circuit is sandwiched between two sheets of
plastic for more protection and flexibility. A complete l Weatherproof-these connectors are most the jumper wire is of too small a gauge, it
printed circuit, consisting of conductors, insulating commonly used where the connector is exposed to
may overheat and possibly melt. Never use
material and connectors for lamps or other compo- the elements. Terminals are protected against mois-
nents is called a printed circuit board. Printed cir- ture and dirt by sealing rings which provide a weath- jumpers to bypass high resistance loads in a
et-tight seal. All repairs require the use of a special circuit. Bypassing resistances, in effect, cre-
cuitry is used in place of individual wires or har- ates a short circuit. This may, in turn, cause
nesses in places where space is limited, such as terminal and the tool required to service it. Unlike
behind instrument panels. standard blade type terminals, these weatherproof damage and fire. Jumper wires should only
be used to bypass lengths of wire or to simu-
Since automotive electrical systems are very sen- terminals cannot be straightened once they are bent. late switches.
sitive to changes in resistance, the selection of prop- ‘Make certain that the connectors are properly seated
erly sized wires is critical when systems are repaired, and all of the sealing rings are in place when con-
netting leads. Jumper wires are simple, yet extremely valuable,
A loose or corroded connection or a replacement wire pieces of test equipment. They are basically test wires
that is too small for the circuit will add extra resis-
l Molded-these connectors require complete which are used to bypass sections of a circuit. Al-
replacement of the connector if found to be defective.
tance and an additional voltage drop to the circuit. though jumper wires can be purchased, they are usu-
The wire gauge number is an expression of the This means splicing a new connector assembly into ally fabricated from lengths of standard automotive
cross-section area of the conductor. Vehicles from the harness. All splices should be soldered to insure
proper contact. Use care when probing the connec- wire and whatever type of connector (alligator clip,
countries that use the metric system will typically de- spade connector or pin connector) that is required for
scribe the wire size as its cross-sectional area in tions or replacing terminals in them, as it is possible
square millimeters. In this method, the larger the to create a short circuit between opposite terminals. If the particular application being tested. In cramped,
hard-to-reach areas, it is advisable to have insulated
wire, the greater the number. Another common sys- this happens to the wrong terminal pair, it is possible
to damage certain components. Always use jumper boots over the jumper wire terminals in order to pre-
tern for expressing wire size is the American Wire vent accidental grounding. It is also advisable to in-
Gauge (AWG) system. As gauge number increases, wires between connectors for circuit checking and
NEVER probe through weatherproof seals. elude a standard automotive fuse in any jumper wire.
area decreases and the wire becomes smaller. An 18
gauge wire is smaller than a 4 gauge wire. A wire
l Hard Shell-unlike molded connectors, the This is commonly referred to as a “fused jumper”. By
inserting an in-line fuse holder between a set of test
terminal contacts in hard-shell connectors can be re-
with a higher gauge number will carry less current
placed. Replacement usually involves the use of a leads, a fused jumper wire can be used for bypassing :
than a wire with a lower gauge number. Gauge wire open circuits. Use a 5 amp fuse to provide protection
size refers to the size of the strands of the conductor, special terminal removal tool that depresses the lock- against voltage spikes.
not the size of the complete wire with insulator. It is ing tangs (barbs) on the connector terminal and al-
lows the connector to be removed from the rear of the Jumper wires are used primarily to locate open
possible, therefore, to have two wires of the same
shell. The connector shell should be replaced if it electrical circuits, on either the ground (-) side of the
gauge with different diameters because one may have
thicker insulation than the other. shows any evidence of burning, melting, cracks, or circuit or on the power (+) side. If an electrical corn-
breaks. Replace individual terminals that are burnt, ponent fails to operate, connect the jumper wire be-
It is essential to understand how a circuit works
corroded, distorted or loose. tween the component and a good ground. If the corn-
before trying to figure out why it doesn’t. An electrical ponent operates only with the jumper installed, the
schematic shows the electrical current paths when a ground circuit is open. If the ground circuit is good,
circuit is operating properly. Schematics break the but the component does not operate, the circuit be-
entire electrical system down into individual circuits. tween the power feed and component may be open. ’
In a schematic, usually no attempt is made to repre- Pinpointing the exact cause of trouble in an elec- By moving the jumper wire successively back from
trical circuit is most times accomplished by the use the component toward the power source, you can
; : sent wiring and components as they physically ap-
pear on the vehicle; switches and other components of special test equipment. The following describes isolate the area of the circuit where the open is lo-
are shown as simply as possible. Face views of har- different types of commonly used test equipment and cated. When the component stops functioning, or the f
j
ness connectors show the cavity or terminal locations briefly explains how to use them in diagnosis. In ad- power is cut off, the open is in the segment of wire j
in all multi-pin connectors to help locate test points. dition to the information covered below, the tool between the jumper and the point previously tested.
! manufacturer’s instructions booklet (provided with You can sometimes connect the jumper wire di-
the tester) should be read and clearly under.$ood be- rectly from the battery to the “hot” terminal of the I
CONNECTORS 1 fore attempting any test procedures. component, but first make sure the component uses 1
# See Figures 5 and 6 JUMPER WIRES 12 volts in operation. Some electrical components, i
such as fuel injectors or sensors, are designed to op-
Three types of connectors are commonly used in erate on about 4 to 5 volts, and running 12 volts di- j
)
automotive applications-weatherproof, molded and rectly to these components will cause damage.
hard shell.
Never use jumper wires made from a thinner TEST LIGHTS I
gauge wire than the circuit being tested. If
# See Figure 7
The test light is used to check circuits and compo-
I nents while electrical current is flowing through
Fig. 5 Hard shell (left) and weatherproof
(right) connectors have replaceable termi- Fig. 7 A 12 volt test light is used to di%
nals
ements 1 the presence of voltage in a circuit

CHASSIS ELECTRiCAL 6-5
them. It is used for voltage and ground tests. To use voltmeter has a positive and a negative lead. To avoid
a 12 volt test light, connect the ground clip to a good damage to the meter, always connect the negative
ground and probe wherever necessary with the pick. lead to the negative (-) side of the circuit (to ground
The test light will illuminate when voltage is detected. or nearest the ground side of the circuit) and connect
This
does not necessarily mean that 12 volts (or any the positive lead to the positive(t) side of the circuit When diagnosing a specific problem, organized
troubleshooting is a must. The complexity of a mod-
particular amount of voltage) is present; it only (to the power source or the nearest power source).
means that some voltage is present. It is advisable Note that the negative voltmeter lead will always be ern automotive vehicle demands that you approach
before using the test light to touch its ground clip black and that the positive voltmeter will always be any problem in a logical, organized manner. There
and probe across the battery posts or terminals to some color other than black (usually red). are certain troubleshooting techniques, however,
which are standard:
make sure the light is operating properly.
l Ohmmeter-the ohmmeter is designed to read l Establish when the problem occurs. Does the
resistance (measured in ohms) in a circuit or compo-
nent. Most ohmmeters will have a selector switch problem appear only under certain conditions? Were
there any noises, odors or other unusual symptoms?
Do not use a test light to probe electronic ig- which permits the measurement of different ranges of
Isolate the problem area. To do this, make some sim-
nition, spark plug or coil wires. Never use a resistance (usually the selector switch allows the
multiplication of the meter reading by 10,100,1,000 ple tests and observations, then eliminate the sys-
pick-type test light to probe wiring on com- terns that are working properly. Check for obvious
puter controlled systems unless specifically and 10,000). Some ohmmeters are “auto-ranging”
which means the meter itself will determine which problems, such as broken wires and loose or dirty
instructed to do so. Any wire insulation that
scale to use. Since the meters are powered by an in- connections. Always check the obvious before as-
is pierced by the test light probe should be
ternal battery, the ohmmeter can be used like a self- suming something complicated is the cause.
taped and sealed with silicone after testing.
l Test for problems systematically to determine
powered test light. When the ohmmeter is connected,
the cause once the problem area is isolated. Are all
Like the jumper wire, the 12 volt test light is used current from the ohmmeter flows through the circuit
the components functioning properly? Is there power
to isolate opens in circuits. But, whereas the jumper or component being tested. Since the ohmmeter’s in-
ternal resistance and voltage are known values, the going to electrical switches and motors. Performing
wire is used to bypass the open to operate the load,
amount of current flow through the meter depends on careful, systematic checks will often turn up most
the 12 volt test light is used to locate the presence of
the resistance of the circuit or component being causes on the first inspection, without wasting time
voltage in a circuit. If the test light illuminates, there
tested. The ohmmeter can also be used to perform a checking components that have little or no relation-
is power up to that point in the circuit; if the test light ship to the problem.
does not illuminate, there is an open circuit (no continuity test for suspected open circuits. In using
the meter for making continuity checks, do not be
l Test all repairs after the work is done to make
power). Move the test light in successive steps back
concerned with the
actual resistance readings. Zero sure that the problem is fixed. Some causes can be
toward the power source until the light in the handle traced to more than one component, so a careful veri-
illuminates. The open is between the probe and a resistance, or any ohm reading, indicates continuity
fication of repair work is important in order to pick up
point which was previously probed. in the circuit, Infinite resistance indicates an opening
in the circuit. A high resistance reading where there additional malfunctions that may cause a problem to
The self-powered test light is similar in design to
should be none indicates a problem in the circuit. reappear or a different problem to arise. A blown
the 12 volt test light, but contains a 1.5 volt penlight
Checks for short circuits are made in the same man- fuse, for example, is a simple problem that may re-
battery in the handle. It is most often used in place of
ner as checks for open circuits, except that the circuit quire more than another fuse to repair. If you don’t
a multimeter to check for open or short circuits when look for a problem that caused a fuse to blow, a
power is isolated from the circuit (continuity test). must be isolated from both power and normal
ground. Infinite resistance indicates no continuity, shorted wire (for example) may go undetected.
The battery in a self-powered test light does not Experience has shown that most problems tend
provide much current. A weak battery may not pro- while zero resistance indicates a dead short.
to be the result of a fairly simple and obvious
vide enough power to illuminate the test light even I ’ cause, such as loose or corroded connectors, bad
when a complete circuit is made (especially if there is grounds or damaged wire insulation which causes a
high resistance in the circuit). Always make sure that Never use an ohmmeter to check the resis- short. This makes careful visual inspection of com-
the test battery is strong. To check the battery, briefly tance of a component or wire while there is ponents during testing essential to quick and accu-
touch the ground clip to the probe; if the light glows voltage applied to the circuit. rate troubleshooting.
brightly, the battery is strong enough for testing.
*A self-powered test light should not be
l Ammeter-an ammeter measures the amount
- I
used on any computer controlled system or of current flowing through a circuit in units called
component. The small amount of electricity amperes or amps. At normal operating voltage, most
circuits have a characteristic amount of amperes, OPEN CIRCUITS
transmitted by the test light is enough to
damage many electronic automotive compo- called “current draw” which can be measured using
an ammeter. By referring to a specified current draw # See Figure 8
nents.
rating, then measuring the amperes and comparing
MULTIMETERS the two values, one can determine what is happening
within the circuit to aid in diagnosis. An open circuit,
for example, will not allow any current to flow, so the
Multimeters are an extremely useful tool for trou-
bleshooting electrical problems. They can be pur- ammeter reading will be zero. A damaged component
or circuit will have an increased current draw, so the
chased in either analog or digital form and have a
reading will be high. The ammeter is always con-
price range to suit any budget. A multimeter is a volt-
netted in series with the circuit being tested. All of
meter, ammeter and ohmmeter (along with other fea-
the current that normally flows through the circuit
tures) combined into one instrument. It is often used
must also flow through the ammeter; if there is any
when testing solid state circuits because of its high
other path for the current to follow, the ammeter read-
input impedance (usually 10 megaohms or more). A
ing will not be accurate. The ammeter itself has very
brief description of the multiieter main test functions
follows: little resistance to current flow and, therefore, will not
affect the circuit, but it will measure current draw only
l Voltmeter--the voltmeter is used to measure
when the circuit is closed and electricity is flowing.
voltage at any point in a circuit, or to measure the
Excessive current draw can blow fuses and drain the
voltage drop across any part of a circuit. Voltmeters
battery, while a reduced current draw can cause mo-
usually have various scales and a selector switch to
tors to run slowly, lights to dim and other compo-
allow the reading of different voltage ranges. The
nents to not operate properly.