AVI ASE-A8, Руководство пользователя, Страница: 41 / 130

correct tools and procedures. Follow the specific in-
structions of the vehicle and equipment manufacturers
when connecting and operating test equipment.
Keep in mind, the scan tool will not reveal the exact na-
ture of the problem, but does help you isolate the circuit
or component where the malfunction exists. Scan tools
provide the user with many different forms of informa-
tion. Compare the scan tool readings with the specifi-
cations from the service publications to determine if, in
fact, a problem exists.
Primary Circuit Testing
Primary circuit voltage has a direct effect on secondary
circuit voltage. The loss of a single volt in the primary
circuit can reduce secondary circuit voltage by as much
as 10 kilovolt (10,000 volts). Common causes of prima-
ry circuit voltage loss include: high circuit resistance, in-
sufficient source voltage from the battery, and low
charging system output.
Symptom Definition Possible Causes
NO START WI TH NORMAL
CRANK SPEED The starter cranks the engine
normally but the engine does
not start.
Primary ignition circuit
failure
No RPM signal to ECM /
Ignition Module
Wet secondary ignition
system components
HARD STARTING / LONG
CRANKING TIME The starter cranks the engine
normally but requires
excessive crank time to start.
Incorrect ignition timing
Deficient spark intensity
Excessive resistance in
primary circuit
STARTS AND STALLS Engine starts but stalls when
the key is released to the RUN
position.
Incorrect ignition timing
Deficient spark intensity
Ignition RUN circuit failure
STALLS AND MAY OR MAY
NOT RESTART Engine stops running under
load, usually at idle when the
transmission is in gear. Engine
may or may not restart quickly.
Incorrect ignition timing
Deficient spark intensity
Interruption of ignition
spark
High resistance in the
primary circuit
RUNS ROUGH / MISFIRES Inconsistent production of
power. Cau ses a noticeable
vibration.
Inconsistent ignition
Deficient spark intensity in
one or more cylinders
Defective spark plug wires
STUMBLE / SURGE
BUCKS / JERKS A drop off of power between
the time the throttle opens and
speed increases.
Deficient spark intensity
High resistance in the
primary circuit
Defective spark plug wires
LACK OF POWER Excessive throttle application
is required to maintain cruise.
Acceleration is slower than
normal.
Incorrect ignition timing
Deficient spark intensity
POOR FUEL ECONOMY Vehicle uses excessive fuel.
Incorrect ignition timing
Deficient spark intensity to
one or more cylinders
Defective spark plug wires
EMISSIONS TEST FAILURE Vehicle fails one or more
emissions tests.
Incorrect ignition timing
Deficient spark intensity or
duration
Excessive resistance in
primary circuit
Fig. 2-1. Ignition system driveability diagnostic procedures.
Chapter
B
: Ignition System Diagnosis and Repair
35