1991 FORD FESTIVA jump start terminals

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F - BASIC TESTING
1991-92 ENGINE PERFORMANCE Ford Motor Co. Basic Diagnostic Procedures
INTRODUCTION
The following diagnostic steps help prevent overlooking simple problems and begin diagnosis for a no-start condition.
The first step in diagnosing any driveability problem is to verify the complaint. Test drive the vehicle under the conditions in which the
problem reportedly occurred.
Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical
breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test
listed in this article.
PRELIMINARY INSPECTION & ADJUSTMENTS
VISUAL INSPECTION
Perform a visual inspection of all electrical wiring. Look for chafed, stretched, cut or pinched wiring. Ensure electrical connections fit tightly
and are not corroded. Ensure vacuum hoses are properly routed and are not cut or pinched. If necessary, see VACUUM DIAGRAMS article in
the ENGINE PERFORMANCE Section to verify routing and connections. Inspect air induction system for possible vacuum leaks.
MECHANICAL INSPECTION
Compression
Engine mechanical condition can be checked using a compression gauge, vacuum gauge or engine analyzer. See engine analyzer instruction
manual for specific instructions. Lowest compression reading must be not less than 75 percent of highest reading.
Exhaust System Backpressure
Exhaust system can be checked with a vacuum gauge or a 0-5 psi pressure gauge. If a pressure gauge is used, remove O2 sensor. Connect gauge
to O2 sensor port. Start engine, and run at 2500 RPM. If exhaust system backpressure is more than 2 psi, exhaust system or catalytic converter
is plugged.
If a vacuum gauge is used, connect it to intake manifold vacuum. Start engine. Observe vacuum gauge. Open throttle part way and hold steady.
If vacuum gauge drops slowly after stabilizing, check exhaust system for a restriction.
FUEL PRESSURE
Fuel Pressure Release
Start engine (if possible), and unplug VAF meter connector. When engine stalls, turn ignition off and reconnect VAF meter wiring. Usin g sh o p
towel, cover fitting to absorb leakage when opening fuel system.
Fuel Pressure Check
1. Connect fuel pressure gauge between fuel filter and fuel rail. Open main valve, and close drain valve. Locate fuel pump check connector
in engine compartment, near left strut. Connect jumper wire between fuel pump test terminals (Black and Green/White wires on Capri
or Black and Green/Red wires on Festiva).
2. Turn ignition on to activate fuel pump. If pump does not run, check fuel pump circuit. If possible, start engine. Measure and record fuel
pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS
article. Disconnect vacuum from pressure
regulator. Turn engine off. Wait 5 minutes and ensure residual pressure is at least 21 psi (1.5 kg/cm
2 ).
3. Operate fuel pump by reconnecting jumper wire at fuel pump check connector. Check fuel pump performance. Pinch hose between
pressure gauge and fuel filter. Do not hold longer than necessary to check pressure.For fuel pressure specifications, see FUEL
PRESSURE SPECIFICATIONS article. If pump does not meet specifications, check fuel pump circuit, fuel pump, fuel tank and fuel
filter or replace fuel pump.
FUEL PUMP PERFORMANCE NOTE:Unless stated otherwise in test procedure, perform all voltage tests with a Digital Volt-Ohm m eter
(DVOM) with a m inim um 10-m egohm input im pedance.
CAUT ION: DO NOT use ignition switch during com pression tests on fuel injected vehicles. Fuel injectors are
triggered by ignition switch during cranking m ode. Use a rem ote starter to crank engine to prevent fire
hazard and catalytic converter and engine oiling system contam ination.
WARNING:ALWAYS relieve fuel pressure before disconnecting any fuel injection system com ponent. DO NOT
allow fuel to contact engine or electrical com ponents.
NOTE:For 1991 fuel pressure specifications, see FUEL PRESSURE SPECIFICAT IONS
article. For 1992 fuel
pressure specifications, see FUEL PRESSURE SPECIFICAT IONS
article.
ApplicationPressure psi (kg/cm2 )Min. Vol. in 10 sec. Ozs. (cc)
Capri(1) 5.5 (167)
Festiva(1) 7.4 (220)
Page 1 of 4 MITCHELL 1 ARTICLE - F - BASIC TESTING 1991-92 ENGINE PERFORMANCE Ford Motor Co. Basic Diagnostic Proced
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memory. Intermittent failures may be caused by a sensor, connector, or wiring. See INTERMITTENTS in TESTS W/O CODES article in the
ENGINE PERFORMANCE Section.
VISUAL CHECK & VEHICLE PREPARATION
Before connecting any equipment to diagnose EEC system, perform following preparatory procedures:
Verify condition of air cleaner and air ducts.
Check all vacuum hoses for leaks, restrictions, or improper routing.
Check EEC system wiring harness electrical connections for corrosion, bent or broken pins, loose wires or terminals, or improper
routing.
Check ECA, sensors, and actuators for physical damage.
Check engine oil and coolant level.
Perform all necessary safety precautions to prevent personal injury or vehicle damage.
Set parking brake. Place shift lever in Park for automatic transmissions, or Neutral for manual transmissions. DO NOT move shift lever
during test unless specifically directed.
Turn off all lights and accessories. Ensure vehicle doors are closed when measuring voltage or resistance.
Start engine. Run at idle until upper radiator hose is hot and pressurized and engine is off fast idle. Check for leaks around exhaust
manifold, exhaust gas oxygen sensor, and vacuum hose connections.
Turn ignition off. Service items as required. Go to EQUIPMENT HOOK-UP .
EQUIPMENT HOOK-UP
VOM
1. Turn ignition off. Connect a jumper wire from STI connector to ground. Refer to SELF-TEST CONNECTOR LOCATION and
SELF
-TEST CONNECTOR WIRE COLORS tables. See Fig. 1 .
2. Connect VOM between STO terminal and engine ground. Set VOM to measure 0-20 volts DC.
CHECK ENGINE Light (MIL)
Connect a jumper wire between STI connector and ground.
SUPER STAR II Tester
Turn ignition off. Connect adapter cable leads to diagnostic tester. Connect service adapter cables to vehicle self-test connectors. Ground
adapter cable.
SELF-TEST CONNECTOR LOCATION
SELF-TEST CONNECTOR WIRE COLORS

Fig. 1: Self
-Test Connector Terminal ID
Courtesy of FORD MOTOR CO.
RETRIEVING CODES
Reading Service Codes
ApplicationLocation
1.3LLeft Rear Corner Of Engine Compartment
1.6LRight Rear Corner Of Engine Compartment
CircuitWire Color
1.3L
SMLBlue/Green
STIYellow/Green
STOYellow/White
1.6L
SMLBlack/Blue
STIYellow
STOGreen/Black
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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 n o id l igh t 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 the types of
injector circuits that your noid lights are designed for. There are three. They are:
Systems with a voltage controlled injector driver. Another way to say it: The noid light is designed for a circuit with a "high" resistance
injector (generally 12 ohms or above).
Systems with a current controlled injector driver. Another way to say it: The noid light is designed for a circuit with a low resistance
injector (generally less than 12 ohms) without an external injector resistor.
Systems with a voltage controlled injector driver and an external injector resistor. Another way of saying it: The noid light is designed
for a circuit with a low resistance injector (generally less than 12 ohms) and an external injector resistor.
If you are not sure which type of circuit your noid light is designed for, plug it into a known good car and check out the results. If it flashes
normally during cranking, determine the circuit type by finding out injector resistance and if an external injector resistor is used. You now
know enough to identify the type of injector circuit. Label the noid light appropriately.
Next time you need to use a noid light for diagnosis, determine what type of injector circuit you are dealing with and select the appropriate
noid light.
Of course, if you suspect a no-pulse condition you could plug in any one whose connector fit without fear of misdiagnosis. This is because it is
unimportant if the flashing light is dim or bright. It is only important that it flashes.
In any cases of doubt regarding the use of a noid light, a lab scope will overcome all inherent weaknesses.
OVERVIEW OF DVOM
A DVOM is typically used to check injector resistance and available voltage at the injector. Some techs also use it check injector on-time
either with a built-in feature or by using the dwell/duty function.
There are situations where the DVOM performs these checks dependably, and other situations where it can deceive you. It is important to be
aware of these strengths and weaknesses. We will cover the topics above in the following text.
Checking Injector Resistance
If a short in an injector coil winding is constant, an ohmmeter will accurately identify the lower resistance. The same is true with an open
winding. Unfortunately, an intermittent short is an exception. A faulty injector with an intermittent short will show "good" if the ohmmeter
cannot force the short to occur during testing.
Alcohol in fuel typically causes an intermittent short, happening only when the injector coil is hot and loaded by a current high e n o u gh t o
jump the air gap between two bare windings or to break down any oxides that may have formed between them.
When you measure resistance with an ohmmeter, you are only applying a small current of a few milliamps. This is nowhere near enough to
load the coil sufficiently to detect most problems. As a result, most resistance checks identify intermittently shorted injectors as being normal.
There are two methods to get around this limitation. The first is to purchase an tool that checks injector coil windings under 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. NOTE:Som e noid lights can m eet both the second and third categories sim ultaneously.
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