GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 32)

BUILD MILLISECONDS
These readings are useful for checking current-regulating ignitions that take a fixed
time to build coil current. Typical build time is 3 to 4 mSec. This time is nearly constant
up to about 3000 RPM, and then begins to shorten as RPM increases. If battery
voltage is low, build times will lengthen.
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Per Coil 1-6 8-5 4-7 6-2
Build time is a function of battery voltage, the inductance of the coil primary, and the
peak amps level at which the ignition module is set to regulate. The following
relationships exist, if other factors are constant.
If:
Ignition Module Current Level is Low........... Build Time will be ................ Shorter
Ignition Module Current is High ................... Build Time will be ................ Longer
Battery Voltage is Low ................................. All Build Times will be ......... Longer
Battery Voltage is High ................................ All Build Times will be ......... Shorter
Coil Inductance is High ................................ Build Time will be ................ Longer
Coil Inductance is Low ................................. Build Time will be ................ Shorter
Primary Circuit Resistance is High ............... Build Time may be .............. Longer and
Peak Amps may be ............. Lower
Long build time may be caused by high resistance in the primary circuit. Remember
that the coil primary circuit includes the power feed, the coil primary, the drive module,
and its connection to ground. Increased resistance from loose or corroded connections
limits the primary current. This may cause lower peak amps or longer build time readings.
Short build time may be caused by shorted coil windings.
Build time will be slightly longer while cranking, because of reduced battery voltage. If
the ignition module is not regulating at all, then Peak Amps can be High and Build can
be Long. Both will be limited only by the primary circuit resistance and battery voltage.
The Primary Ignition Troubleshooting Chart on the facing page will help you determine
which component(s) may be bad.
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