GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 66)

FUEL INJECTORS
Press FUEL SYSTEM - GAS ANALYSIS, SELECT Injector Drive , and press NEXT. A screen
will appear, prompting you to put the black Primary Amps probe around the injector wire and
to vary RPM to set minimum and maximum drive times.
Press NEXT, and this screen will appear:
FUEL INJECTOR - AMPS Battery 14.25 Volt
839 RPM 5.2 PkAmp Build 1.3 mS
Min Pulse Width mS Max
1.6 2.4 7.5
6-1
Peak Amps (PkAmp) shows the peak
current driving the injector. It is regulated by
the driver. Typical peak readings for one
injector are 4 amps for current regulated
drivers, and 0.7 amps for resistance limited
drivers. Compare one driver bank to another.
Build Time, or ramp time in milliSeconds
(mS) is affected by the solenoid and the
pintle movement. Slightly shorter-than-
normal Build Time can be caused by a
solenoid winding short or an injector that is
stuck. Slightly longer could be from a bad
driver or wire connection. Typically, build time
is 1.3 mS.
Pulse Width is shown on the lower display
line. It lets you see if the injector is actively
driven. Use momentary wide open throttle to
see the Min and Max range. The center
reading shows what is presently happening.
The NEXT key clears the Min and Max so
they can begin accumulating again. Up to 99
milliSeconds can be measured. Readings
depend upon power demand and vary from
build time to over 30 mS.
No readings will be displayed if there are no
amps pulses, or if the pickup is reversed, or
around both wires of an injector.
FUEL INJECTION CIRCUIT TYPES
Sequential - Each injector has a separate
driver and can be driven independently of the
other injectors. The build time currents can
overlap on these systems; for valid readings
check each injector separately.
Pairs - There is one driver for each pair of
injectors. The current readings, as measured
through the common supply wire, will be
twice the reading expected for a single
injector.
Banks - Half of cylinders are driven
alternately. The current readings as
measured through the common supply wire
will be 2, 3, or 4 times the reading expected
for a single injector.
Injector drivers generally employ a current
limiting scheme. The current builds to a
maximum level and is then limited by the
components.