GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 37)

FIRING KV — Live and Maximum
Firing KV is the voltage that is required to start ionizing the air/fuel mix in the spark plug gap.
For the ignition to always work, the KV available from the coil must be more than the highest
KV requirement. Causes of high KV can be a wide or worn plug gap, a broken sparkwire
conductor, or a lean fuel mixture. Unusually low KV can be from a fouled plug gap, secondary
insulation failure, or low compression.
Typical live KV is 5 to 10 at a steady RPM with not more than a 5 KV difference between the
highest and lowest. On double output coils, the exhaust spark is normally less than 4 KV.
Maximum KV is required when accelerating under load. Applying momentary wide open throttle,
without letting the engine over-rev, makes an easy test for Max KV. The initial test screen has
a reminder for this procedure.
EXHAUST KV
Also known as waste KV. On double output coils, the spark plug in the cylinder on its exhaust
stroke serves as the ground path for the coil. Exhaust KV should be low because, without
compression in the cylinder, little voltage should be needed to fire the plug. Exhaust spark is
normally less than 4 KV. Higher readings indicate the possibility of a broken spark plug wire,
a wide plug gap, or a fouled plug on the opposite side.
INDIVIDUAL CYLINDER READINGS
There are four additional screens that show data for the individual cylinders. Press SELECT
to step through the screens.
The burn time bar graph screen shows live spark burn durations for each cylinder. The number
in the upper left corner shows the average reading for all cylinders.
Burn (Avg)о о я н п ь п н
1.2 mS яя я
Ω
яя я
Ω
яя я
π
яя яя
~ ¤я £я £я £я ¢я ¡я £я ¤я
Cyl 1 2 3 4 5 6 7 8
The bottom of the left bar represents the minimum burn duration and the top is the maximum.
The top of the right bar shows the live reading. Press HELP to see this screen.
Max mS---~ь
яь ---Live mS
Min mS-------~£ÿ
Cylinder--------------~ 1
4-8