Volkswagen New Beetle. Manual - part 168

 

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Volkswagen New Beetle. Manual - part 168

 

 

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 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Waveforms - Injector Pattern Tutorial

  

manufacturer.  

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

EXAMPLE #5 - CURRENT CONTROLLED DRIVER 

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

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Waveforms - Injector Pattern Tutorial

  

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

EXAMPLE #7 - CURRENT CONTROLLED DRIVER 

The known-good current controlled type waveform in Fig. 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

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Waveforms - Injector Pattern Tutorial

  

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. Fig. 18 illustrates the 64 
volt inductive kick on this engine, indicating no clamping is occurring. The second pattern, Fig. Fig. 19 , was 
taken during hot idle, closed loop, and no load. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Waveforms - Injector Pattern Tutorial

  

 

 

 

 

 

 

 

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