Owner's manual

To Connect to the Fuel Injector
1. Connect the Inductive Pickup around a single drive
wire going to an injector or bank of injectors. Confirm
the pickup is connected properly by selecting the Drive
Time function. If Drive time is full scale at Idle, the
Pickup is on Backwards.
Measurements
1. Peak Amps is the peak current driving the injector. It
is regulated by the driver. Typical peak readings are
from 1 to 4 amps for a current regulated injector driver,
and about 1 amp for a resistance limited injector driver.
Peak Amps automatically selects the proper range.
Be sure to note which range LED is active.
2. Build Time, is the time it takes the amperage to reach
its maximum. Build Time is affected by the solenoid
and pintle movement. Shorter Build Time can be caused
by a solenoid winding short or an injector that is stuck.
Longer build time could be from a bad driver or wire
connection. Build Time is read on the upper scale.
3. Drive Time is the time the injector is actively driven.
Use momentary wide open throttle to see the Min and
Max readings. Drive Time is read on the lower scale.
Analysis of Test Results
In general, a difference of 1 amp between injector banks
on resistance regulated injectors indicates that one or more
injectors is faulty in the bank with the higher amperage
draw. In a current regulated system, look for build time to
be longer on the bank with an open or high resistance
injector. Build will be shorter on the bank with a shorted
injector.
Using the Fuel Injector Probe with a Labscope
The 71 sends a signal that is scaled at .1 volts (or 100mV)
per amp detected. A 4 amp peak will appear 0.4 volts high
on the labscope. Use a BNC Cable with a BNC to Banana
Adapter (like Ferret P/N W090-10) to adapt the 71 to work
on most labscopes or graphing multimeters.
Technical Support
For additional information or technical assistance, please
contact Ferret Instruments at [phone] or
www.ferretinstruments.com.
OPERATOR’S MANUAL
Fuel Injector Probe 71
FEATURES
Test Fuel Injectors without
piercing wires or backprobing
connectors. Connect to an
individual injector or a bank of
injectors inductively.
Use a LabScope to view the fuel
injector pattern.
20 segment bar graph displays
Peak Amps, Build Time or Drive
Time at the press of a button.
Easily locate open or shorted
injectors by using current
ramping measurements.
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