1991 1999 ford explorer chilton User Manual

							
FUEL TANK
Tank Assembly
REMOVAL & INSTALLATION Disconnect the negative battery cable and relieve the fuel system pressure.
1. 
Siphon or pump as much fuel as possible out through the fuel filler pipe.
2. 
Fuel injected vehicles have reservoirs inside the fuel tank to maintain fuel near the fuel pick-up during
cornering or low-fuel operation. These reservoirs could block siphon hoses or tubes from reaching the
bottom of the fuel tank. Repeated attempts, using different hose orientations, can overcome this
obstacle.
Raise and safely support the vehicle.
3. 
If equipped, remove the skid plate attaching bolts, then lower the plate and remove it.
4. 
On Explorer/Mountaineer models, the front fuel tank strap is bolted to the skid plate and will be
disconnected when the plate is removed.
Disconnect the fuel fill and vent hoses connecting the filler pipe to the tank.
5. 
On vehicles equipped with a metal retainer fastening the filler pipe to the fuel tank, remove the screw
holding the retainer to the fuel tank flange.
6. 
Disengage the fuel lines and the electrical connections to the fuel tank sending unit/fuel pump
assembly. On some vehicles, these are inaccessible on top of the tank. In this case, they must be
disconnected when the tank is partially lowered.
7. 
Place a safety support (such as a floor jack) under the fuel tank and remove the bolts from the fuel
tank straps. Allow the straps to swing out of the way. Be careful not to deform the fuel tank.
8. 
On Ranger vehicles, the rear fuel tank strap has two connections which must be unbolted. Lower the tank a few inches, then detach the fuel lines and electrical connection from the sending
unit/fuel pump assembly, if required.
9. 
Remove the tank from the vehicle.
10. 
FUEL TANK 641 
						

							Exploded view of the Explorer/Mountaineer fuel filler assembly
Click to enlarge
HOW TO USE THIS BOOK
642 REMOVAL & INSTALLATION 
						

							Exploded view of the Explorer/Mountaineer fuel tank assembly
Click to enlarge
HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 643 
						

							Exploded view of the Ranger fuel filler assembly and pump mounting
Click to enlarge
HOW TO USE THIS BOOK
644 REMOVAL & INSTALLATION 
						

							Exploded view of the Ranger Super Cab fuel tank assembly
Click to enlarge
HOW TO USE THIS BOOK
REMOVAL & INSTALLATION 645 
						

							Exploded view of the Ranger Regular Cab fuel tank assembly
Click to enlarge
To install: Before installation, it would be wise to perform the following:Double-check the tightness of the sending unit/fuel pump locking ring. If it is already loose,
now would be a good time to remove it and check the condition of the gasket underneath.
1. 
Ensure that all metal shields are reinstalled in their original positions and that the fasteners are
secure.
2. 
Be sure that the fuel vapor valve is completely installed on top of the fuel tank.
3. 
Make all necessary fuel line or wiring connections which will be inaccessible after the fuel
tank is installed.
4. 
11. 
Raise the fuel tank into position in the vehicle. If necessary, attach the fuel lines and sending unit
electrical connector before the tank is in its final position.
12. 
Lubricate the fuel filler pipe with a water-based lubricant. Install the tank onto the filler pipe, then
bring the tank into final position. Be careful not to deform the tank.
13. 
Position the tank straps around the tank and start the retaining nut or bolt. Align the tank with the
straps. If equipped, be sure the fuel tank shields are installed with the straps and are positioned
correctly.
14. 
Check the hoses and wiring on top of the tank. Make sure they are correctly routed and will not be
pinched between the tank and body.
15. 
Tighten the fuel tank strap retaining nuts or bolts to 20-5 ft. lbs. (3-41 Nm).
16.  HOW TO USE THIS BOOK
646 REMOVAL & INSTALLATION 
						

							If not already attached, connect the fuel hoses and lines. Make sure the fuel supply, fuel return (if
present) and the vapor vent attachments are made properly. If not already attached, connect the
sending unit.
17. 
If removed, install the fuel tank skid plate.
18. 
Lower the vehicle.
19. 
Fill the tank with fuel and check all connections for leaks.
20. 
Sending Unit
REMOVAL & INSTALLATION
Please refer to Fuel Pump, Removal & Installation.
Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning. HOW TO USE THIS BOOK
Sending Unit 647 
						

							
UNDERSTANDING AND TROUBLESHOOTING
ELECTRICAL SYSTEMS
Basic Electrical Theory
For any 12 volt, negative ground, electrical system to operate, the electricity must travel in a complete circuit.
This simply means that current (power) from the positive (+) terminal of the battery must eventually 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 function properly.
Perhaps the easiest way to visualize a circuit is to think of connecting a light bulb (with two wires attached to
it) to the battery-one wire attached to the negative (-) terminal of the battery and the other wire to the positive
(+) terminal. With the two wires touching the battery terminals, the circuit would be complete and the light
bulb would illuminate. Electricity would follow a path from the battery to the bulb and back to the battery. Its
easy to see that with longer wires on our light bulb, it could be mounted anywhere. Further, one wire could be
fitted with a switch so that the light could be turned on and off.
This example illustrates a simple circuit. When the switch is closed, power from the positive (+)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 terminal. 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
The normal automotive circuit differs from this simple example in two ways. First, 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 contain multiple
components which receive power from a single circuit. This lessens the amount of wire needed to power
components on the vehicle.
HOW DOES ELECTRICITY WORK: 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 an atom. The center core is comprised of protons (positive charge)
and neutrons (neutral charge). Electrons 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
UNDERSTANDING AND TROUBLESHOOTING ELECTRICAL SYSTEMS 649 
						

							
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 with 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 measurement
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 will 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 units called volts (v). When a voltmeter 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 circuit. The
standard unit for measuring resistance is an ohm. Resistance in a circuit varies depending on the amount and
type of components used in the circuit. The main factors which determine resistance are:
Material-some materials have more resistance than others. Those with high resistance are said to be
insulators. Rubber materials (or rubber-like plastics) 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 conductors. 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.
· 
Size-the larger the wire size being used, the less resistance the wire will have. This is why
components which use large amounts of electricity usually have large wires supplying current to
them.
· 
Length-for a given thickness of wire, the longer the wire, the greater the resistance. The shorter the
wire, the less the resistance. When determining 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.
· 
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
temperatures (negative temperature coefficient). These principles are used in many of the sensors on
the engine.
· 
OHMS LAW
There is a direct relationship between current, voltage and resistance. The relationship between current,
voltage and resistance can be summed up by a statement known as Ohms law.
Voltage (E) is equal to amperage (I) times resistance (R): E=I 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 resistance of a circuit goes up, the amount of current that flows in
the circuit will go down, if voltage remains 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: HOW TO USE THIS BOOK
650 HOW DOES ELECTRICITY WORK: THE WATER ANALOGY 
						

							
Power (w) is equal to amperage (I) times voltage (E): W=I 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.
Electrical Components
POWER SOURCE
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 vehicles 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 subsections
(cells) connected in series, so that the unit is capable of producing approximately 12 volts of electrical
pressure. Each subsection consists of a series of positive and negative plates held a short distance apart in a
solution of sulfuric acid and water.
The two types of plates are of dissimilar metals. This sets up a chemical reaction, and it is this reaction which
produces current flow from the battery when its positive and negative terminals are connected 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 isnt an alternator, but a generator. The difference is that an alternator supplies
alternating current which is then changed to direct 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
electromagnets. 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.
GROUND
Two types of grounds are used in automotive electric circuits. Direct ground components are grounded to the
frame through their mounting points. All other components use some sort of ground wire which is attached to
the frame or chassis of the vehicle. The electrical current runs through the chassis of the vehicle and returns to
the battery through the ground (-) cable; if you look, youll see that the battery ground cable connects between
the battery and the frame or chassis of the vehicle.
It should be noted that a good percentage of electrical problems can be traced to bad grounds.
PROTECTIVE DEVICES
It is possible for large surges of current to pass through the electrical system of your vehicle. If this surge of HOW TO USE THIS BOOK
OHMS LAW 651