GxT Ferret 63 DIAGNOSTIC ENGINE ANALYZER - Manual (Page 18)

“SPARK BURN” KEY
Measures secondary spark events. Continuous operation
of all the spark plugs can be watched
with this test. The Average, Minimum,
Maximum, and Slope cylinder data can
be chosen with SELECT. "Min" holds
the shortest milliSeconds, and "Max"
holds the longest. Diagnostic messages
will be set by the analyzer if symptoms appear regularly,
but will go away if the symptoms are reduced. The mea-
surements for this test come from the ignition coil primary
signal that “reflects” the coil secondary events.
Spark Burn Analysis has an entry instruction:
The "briefly open throttle" procedure captures the operat-
ing limits burn times. The analyzer checks for excessive
open throttle RPM and may inform the user to redo the
"open throttle" step. Such as;
If this happens, press START and then "briefly open
throttle", but do not let the RPM get so high.
The first data display shows the Spark Burn milliSeconds
and Spark Slope averages of all the cylinders.
Press SELECT to change between the average, mini-
mum, maximum, and slope spark plug data displays.
The "mSec" screen gives the average reading from each
spark plug. Use it to watch individual cylinders as engine
operation is varied. The "Min" screen is used to find cyl-
inders with short reserves. The "Max" screen is used to
find insulation failures and fouled plugs.
To clear the "Min" and "Max" numbers press START.
When more than 8 cylinders are displayed there will be
a "Bank A" or "Bank B" shown for the first half or second
half of the firing sequence.
Compare each cylinderʼs average Burn Time to the oth-
ers. A 0.3 difference from the displayed average is sig-
nificant. When comparing Slopes, a consistent difference
of 20 above or below the measured average should be
investigated further.
BURN TIME
This is the duration of a spark in milliSeconds. It is af-
fected by the energy available to push the spark current
through the plug circuit. If there is little resistance to
block the current it will go longer, more resistance and
it will burn out quicker. The usual time is about 1.5 mil-
liSeconds (mS) with 0.8 to 2.3 milliSeconds the typical
range limits.
Some ignitions may be designed for longer or shorter
spark durations. Compare similar engines if in doubt.
Short Burn Time is caused by breaks in secondary igni-
tion wires, wide sparkplug gaps, worn plug and rotor
electrodes, high circuit resistances, and very lean fuel
mixtures.
Long Burn Time comes from narrow or fouled plug gaps,
distributor or insulation shorts, rich fuel mixture, and low
cylinder compression. Usually long times seen with the
"Max" data set show intermittent misfires from shorted
secondary insulation in the cap, rotor, wires, or plugs.
A reduction in burn times, with snap acceleration, is only
caused by the change within the plug gap from burning
fuel and pressure. So this test is an ideal check for worn
out spark plugs.
Open the throttle momentarily for engine acceleration to
check the Burn Time reserve. The Min Burn Time dis-
play shows the shortest times measured when an engine
works against its own inertia. Compare these times to
0.8 milliSeconds for the reserve.
Problems with other parts like wire breaks, wide rotor
gaps and high secondary resistance are most easily de-
tected at a moderate and steady RPM such as between
1000 and 2000 since they are not affected by the cylinder
pressures.
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
-16-
COIL WIRE
RESISTANCE
AND GAPS
BROKEN COIL
CAP CRACKS
PLUG WIRES
RESISTANCE
AND GAPS
ROTOR GAP
EROSION AND
CORROSION
WORN TIPS
LEAN MIX
IN GAP
IGNITION SECONDARY CIRCUIT
Briefly Open Throttle
do not exceed 2500 RPM
956 RPM SPARK 1.5mS
IgEgy 38 Slope - 7
SPARK 1.3 0.9 1.5 1.4
mSec msg1.9 1.7 Bank B
TEST INVALID
REDO WITH LOWER RPM