GxT Ferret 63 DIAGNOSTIC ENGINE ANALYZER - Manual (Page 16)

“IGNITION PRIMARY” KEY
Use to check the input power and response of the igni-
tion coil. SELECT the two screens to
see all measurements including Coil
Ignition Energy ("IgEgy"), Coil Oscilla-
tions ("Osc"), Driver Module On Voltage
("Drvr"), Ignition Dwell ("DWL"), and the
Variation of dwell and timing in degrees
("VARIES").
The signal is taken from the coil primary terminal with the
green Coil Primary Clip.
COIL OSCILLATIONS
This is an indicator of liveliness in the ignition coil. Shorts
in coil insulation or in connected components usually
dampen the oscillations so they are reduced or elimi-
nated.
Points driven ignition coils usually show 4 to 8 oscilla-
tions, which are more than electronic ignitions which do
1 to 4. Some Chrysler ignition modules begin dwell im-
mediately after the spark burn time so they normally donʼt
show any oscillations.
DRIVER MODULE / POINTS VOLTAGE
"Drvr" is the voltage during the dwell time. For mechani-
cal points it should be less than 0.3 volts. Electronic
modules typically have 0.5 to 1.5 volts. Ignitions made
alike should compare within 0.2 volts. In this test a high
voltage indicates a failing (high resistance) coil driver
output transistor, bad points, or a high resistance con-
nection to ground.
DWELL
Readings in degrees and percent are useful for setting
mechanical points. MilliSeconds are useful for checking
electronic HEI type ignitions, which take a fixed time to
charge the coil with current. A typical HEI reads about 3.5
mS up to 3000 RPM, and more while cranking.
Use SETUP and SELECT to choose whether dwell is
displayed by degrees (DEG), percent(%), or milliSeconds
(mS). If dwell is displayed in degrees it is scaled accord-
ing to the number of cylinders selected in SETUP.
This analyzer measures dwell according to the interval
that points are closed, or the transistor driver is fully on.
The coil amps dwell hold time which sometimes follows
amps buildup is not included in these readings.
IGNITION ENERGY (See HARD START page12)
SELECT the display showing "VARIES" which reads
RPM, Dwell, Dwell Variation, and Timing Variation.
Variation gauges the engineʼs control stability.
DWELL VARIATION
This is the difference in degrees between the longest and
shortest dwell period. It could be from an unstable coil
drive module. Mechanical sloppiness in the distributor
shaft bearings and cam shaft drive is the prime cause. At
higher speeds on point contact ignitions the problem can
be floating contacts from weak springs and poor lubrica-
tion. Readings should be less than 3 degrees.
TIMING VARIATION
This is the difference in engine shaft degrees of the
longest and the shortest time between ignition firings.
Variations in timing are associated with defective engine
operation. On pre-computer engines variation meant
looseness in the mechanical drive from the crankshaft to
the points cam. This is still generally true for distributor
located ignition sensors, but sometimes timing is inten-
tionally varied by engine computers.
Irregular idle RPM from O2 feedback fuel metering can
cause an apparent timing variation. Operating the en-
gine at higher RPM should reduce the variation to under
3 degrees. The point to be alert to is the erraticness of
timing variation which points to sloppiness in the gears,
bearings and chains leading to the ignition timing sensor.
Confirm timing variation with a Timing Light triggered from
the coil-distributor wire by watching the paired marks.
Read variation from 1000 to 3000 RPM with the RPM
held steady.
SENSOR
TEST
02 TPS
SETUP AMP ZERO SELECT MESSAGE
PRINT
DISPLAY
PRINT
AUTOTEST
CHARGING
STARTING
AMPS VOLTS
IGNITION
PRIMARY
COIL MODULE
DWELL VARIATION
AUXILIARY AUXILIARY PER CYLINDER
CRANKING
ANALYSIS
COMPRESSION
BAT. STARTER ALT.
POWER
BALANCE
% RPM DROP
AUTO MANUAL
PER CYLINDER
SPARK
BURN
SECONDARY
MSEC SLOPE
PER CYLINDER
HARD
START
IGNITION VOLTS
AUXILIARY
FUEL
INJECTION
MSEC, % DUTY, HZ
AUXILIARY
START
PAPER
ADVANCE
957 RPM msg Bat 13.84
Osc 3 IgEgy 38 Drvr 0.8v
-14-
957 RPM msg DWL 3.3mSec
Dwl 0.6 VARIES Tmg 2.9
SPARK
BURN
TIME
INTERMEDIATE
SECTION
COIL
OSCILLATIONS SPARK
LINE
BATTERY
GROUND
DWELL
SECTION
IGNITION CYCLE INTERVAL
MEASURED
DWELL
DWELL
VARIATION
DRIVER
VOLTAGE
DWELL
HOLD
(HEI
TYPES)
COIL PRIMARY SIGNAL