GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 67)

Amps Build Sequential
None None Open circuit, check continuity
Low Long Wiring, connections, or driver
High Short Shorted Winding
Amps Build Banked or Paired
None None Open circuit or bad driver
High ------- Shorted winding
Normal Short Shorted winding, Driver OK
High Long Driver not Limiting
Low Long Open, high resistance, or
bad driver
Primary
Amps
Pickup
To
Driver
+ 12 V
Label Side
Toward
Battery
Plus
Diagnosing Injector Electrical Problems
Sequential systems - Measure each
injector, noting the build and peak current
values. If an injector does not produce any
reading, it is likely that it is open circuit.
Disconnect the plug from the injector, and
check the continuity using an ohmmeter. If
there is no continuity, or the resistance is
extremely high, then the injector is defective.
If an injector has much longer build time or
lower peak current, run a continuity check.
If the injector is normal, then check wiring,
connections and the driver (usually part of
the engine control module).
If an injector has much shorter build time or
higher peak current, then the injector may
have a shorted winding in its coil.
Banked or Paired systems - Measure each
driver branch circuit, noting the build and
peak current values.
If a driver circuit does not produce any
reading, it is likely that there is an open circuit
or defective driver. Disconnect the plugs from
the injectors in the circuit, and check the
continuity. If the injectors are good, then the
driver or connections are defective.
If the branch build time is shorter or peak
current is higher, it is likely that one of the
injectors in the branch is shorted. One
shorted injector in a branch will ‘starve’ the
other injector(s) in that branch of the current
needed to operate. Connect the pickup to
each injector in the branch, and isolate the
defective injector as described in above for
Sequential systems.
If the branch build time is longer, or the peak
current is lower, it is likely that one of the
injectors in the branch is open circuit, there
is high resistance in the circuit, or the driver
is defective. Connect the pickup to each
injector in the branch to determine if an
injector is open. Connecting to an open
injector will produce no build or peak current
measurements.
FUEL INJECTOR HOOKUP
6-2
Fuel Injection Troubleshooting Chart