Mitsubishi Montero (1991+). Manual - part 321

 

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Mitsubishi Montero (1991+). Manual - part 321

 

 

Fig. 5:  Injector Bank w/Excessive Current Flow - Current Pattern

Fig. 6:  Single Injector w/Normal Current Flow - Current Pattern

Fig. 7:  Single Injector w/Excessive Current Flow - Current Pattern

         EXAMPLE #2 - VOLTAGE CONTROLLED DRIVER

         This time we will look at a GM 3.1L V6 VIN [T].  Fig. 8 shows

the 1, 3, 5 (odd) injector bank with the current waveform indicating

about a 2.6 amp draw at idle. This pattern, taken from a known good

vehicle, correctly stays at or below the maximum 2.6 amps current

range. Ideally, the current for each bank should be very close in

comparison.

         Notice the small dimple on the current flow’s rising edge.

This is the actual injector opening or what engineers refer to as the

"set point." For good idle quality, the set point should be uniform

between the banks.

         When discussing Ohm’s Law as it pertains to this parallel

circuit, consider that each injector has specified resistance of 12.2

ohms. Since all three injectors are in parallel the total resistance

of this parallel circuit drops to 4.1 ohms. Fourteen volts divided by

four ohms would pull a maximum of 3.4 amps on this bank of injectors.

However, as we discussed in EXAMPLE #1 above, other factors knock this

value down to roughly the 2.6 amp neighborhood.

         Now we are going to take a look at the even bank of

injectors; injectors 2, 4, and 6. See Fig. 9. Notice this bank peaked

at 1.7 amps at idle as compared to the 2.6 amps peak of the odd bank (

Fig. 8). Current flow between even and odd injectors banks is not

uniform, yet it is not causing a driveability problem. That is because

it is still under the maximum amperage we figured out earlier. But be

aware this vehicle could develop a problem if the amperage flow

increases any more.

         Checking the resistance of this even injector group with a

DVOM yielded 6.2 ohms, while the odd injector group in the previous

example read 4.1 ohms.

Fig. 8:  Injector Odd Bank w/Normal Current Flow - Current Pattern

Fig. 9:  Injector Even Bank w/Normal Current Flow - Current Pattern

         EXAMPLE #3 - VOLTAGE CONTROLLED DRIVER

         Example #3 is of a Ford 5.0L V8 SEFI.  Fig. 10 shows a

waveform of an individual injector at idle with the Lab Scope set on

200 milliamps per division. Notice the dimple in the rising edge. This

dimple indicates the actual opening of the injector (set point)

occurred at 400 milliamps and current peaked at 750 milliamps. This is

a good specification for this engine.

         The next waveform pattern in Fig. 11 shows an abnormality

with another injector. With the Lab Scope set on 500 milliamps per

division, you can see that the current waveform indicates a 1200

milliamp draw. This is a faulty injector.

         Abnormally low resistance injectors create excessive current

draw, causing rough idle, and possible computer driver damage.

Fig. 10:  Single Injector w/Normal Current Flow - Current Pattern

Fig. 11:  Single Injector w/Excessive Current Flow - Current Pattern

         EXAMPLE #4 - CURRENT CONTROLLED DRIVER

         Example #4 is of a Ford 4.6L SEFI VIN [W]. See  Fig. 12 for

the known-good waveform pattern. This Ford system is different from

the one above in EXAMPLE #3 as it peaks at 900 milliamps and the

actual opening of the injector (set point) is just below 600

milliamps.

         This is offered as a comparison against the Ford pattern

listed above, as they are both Ford SEFI injectors but with different

operating ranges. The point is that you should not make any broad

assumptions for any manufacturer.

Fig. 12:  Single Injector w/Normal Current Flow - Current Pattern

         EXAMPLE #5 - CURRENT CONTROLLED DRIVER

         The known-good waveform in Fig. 13 is from a Chrysler 3.0L V6

 

 

 

 

 

 

 

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