1988 JEEP CHEROKEE Service Repair Manual

Fig. 18: Injector Bank - Known Good - Voltage Pattern

Fig. 19: Injector Bank - Known Good - Voltage Pattern
EXAMPLE #2 - VOLTAGE CONTROLLED DRIVER
The known-good waveform pattern in Fig. 20 is from a GM 3.8L
V6 PFI VIN [3]. It was taken during hot idle, closed loop and no load.

Fig. 20: Injector Bank - Known Good - Voltage Pattern
EXAMPLE #3 - VOLTAGE CONTROLLED DRIVER
This known-good waveform pattern, Fig. 21, is from a GM 5.0L
V8 TPI VIN [F]. It was taken during hot idle, closed loop and no load.

Fig. 21: Injector Bank - Known Good - Voltage Pattern
EXAMPLE #4 - CURRENT CONTROLLED DRIVER
From 1984 to 1987, Chrysler used this type injector drive on
their TBI-equipped engines. See Fig. 22 for a known-good pattern.
Instead of the ground side controlling the injector, Chrysler
permanently grounds out the injector and switches the power feed side.
Most systems do not work this way.
These injectors peak at 6 amps of current flow and hold at 1
amp.

Fig. 22: Single Injector - Known Good - Voltage Pattern
EXAMPLE #5 - CURRENT CONTROLLED DRIVER
These two known-good waveform patterns are from a Chrysler 3.
0L V6 VIN [3]. The first waveform, Fig. 23, is a dual trace pattern
that illustrates how Chrysler uses the rising edge of the engine speed
signal to trigger the injectors. The second waveform, Fig. 24, was
taken during hot idle, closed loop, and no load.

Fig. 23: Injector Bank - Known Good - Voltage Pattern

Fig. 24: Injector Bank - Known Good - Voltage Pattern
EXAMPLE #6 - CURRENT CONTROLLED DRIVER
This known-good pattern from a Ford 3.0L V6 PFI VIN [U]
illustrates that a zener diode inside the computer is used to clamp
the injector's inductive kick to 35-volts on this system. See Fig. 25.

Fig. 25: Injector Bank - Known Good - Voltage Pattern
EXAMPLE #7 - CURRENT CONTROLLED DRIVER
This known-good waveform from a Ford 5.0L V8 CFI VIN [F] was
taken during hot idle, closed loop, and no load. See Fig. 26.