Mitsubishi Montero (1991+). Manual — part 322

PFI VIN [3]. It is a perfect example of the peak and hold theory. The

waveform shows a 1-amp per division current flow, ramping to 4 amps

and then decreasing to 1-amp to hold the injector open.

Fig. 13: Injector Bank w/Normal Current Flow - Current Pattern

EXAMPLE #6 - CURRENT CONTROLLED DRIVER

This next known-good waveform is from a Ford 5.0L V8 CFI VIN

[F]. See Fig. 14. The pattern, which is set on a 250 milliamps scale,

indicates a 1.25 amp peak draw and a hold at 350 milliamps.

Fig. 14: Single Injector w/Normal Current Flow - Current Pattern

EXAMPLE #7 - CURRENT CONTROLLED DRIVER

The known-good current controlled type waveform in Fig. 15 is

from a GM 2.0L TBI VIN [1]. With the lab scope set at 2 amps per

division, notice that this system peaks at 4 amps and holds at 1 amp.

The next waveform is from the same type of engine, except

that it shows a faulty injector. See Fig. 16. Notice that the current

went to almost 5 amps and stayed at 1 amp during the hold pattern.

Excessive amounts of current flow from bad injectors are a common

source of intermittent computer shutdown. Using a current waveform

pattern is the most accurate method of pinpointing this problem.

Fig. 15: Single Injector w/Normal Current Flow - Current Pattern

Fig. 16: Single Injector w/Excessive Current Flow - Current Pattern

EXAMPLE #8 - CURRENT CONTROLLED DRIVER

This known-good CPI system waveform from a GM 4.3L V6 CPI VIN

[W] peaks at 4 amps and holds at 1-amp. See Fig. 17 for waveform.

Fig. 17: Single Injector w/Normal Current Flow - Current Pattern

VOLTAGE WAVEFORM SAMPLES

EXAMPLE #1 - VOLTAGE CONTROLLED DRIVER

These two known-good waveform patterns are from a Ford 4.6L

V8 VIN [W]. Fig. 18 illustrates the 64 volt inductive kick on this

engine, indicating no clamping is occurring. The second pattern,

Fig. 19, was taken during hot idle, closed loop, and no load.

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