ISUZU Amigo/Pick-ups/Rodeo/Trooper 1981-1996

Diagnosis and Testing

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See Figures 1, 2, 3, 4, 5, 6, 7 and 8

Before beginning any diagnosis and testing procedures, visually inspect the components of the ignition system and engine control systems. Check for the following:



Discharged battery
 
Damaged or loose connections
 
Damaged electrical insulation
 
Poor coil and spark plug connections
 
Ignition module connections
 
Blown fuses
 
Damaged vacuum hoses
 
Damaged spark plugs
 

Check the spark plug wires and boots for signs of poor insulation that could cause crossfiring. Make sure the battery is fully charged and that all accessories are off during diagnosis and testing. Make sure the idle speed is within specification.

You will need a good quality volt-ohmmeter and a spark tester in order to check the ignition system. A spark tester resembles a spark plug without threads and the side electrode removed. Using a modified spark plug is as a spark tester is not recommended.

When attempting to search for ignition troubles, keep in mind the various sensor inputs which the control module uses to calculate timing may affect engine performance. The PCM will alter timing based on sensor inputs as follows:



Low MAP output voltage = More spark advance
 
Cold engine = More spark advance
 
High MAP output voltage = Less spark advance
 
Hot engine = Less spark advance
 

With this in mind, DETONATION could be caused by low MAP output or high resistance in the coolant sensor circuit. POOR PERFORMANCE could be caused by a high MAP output or low resistance in the coolant sensor circuit.



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Fig. Fig. 1: Schematic of the Electronic Distributor Ignition System-4ZD1 and 4ZE1 engines



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Fig. Fig. 2: Electronic Ignition Diagnostic Chart 1



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Fig. Fig. 3: Electronic Ignition Diagnostic Chart 2



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Fig. Fig. 4: Electronic Ignition Diagnostic Chart 3



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Fig. Fig. 5: Electronic Ignition Diagnostic Chart 4



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Fig. Fig. 6: Schematic of the Electronic Distributor Ignition System-V6 Trooper



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Fig. Fig. 7: Schematic of the Electronic Distributor Ignition System-V6 Rodeo



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Fig. Fig. 8: Electronic Ignition Diagnostic Chart-V6 engine

INPUT VOLTAGE TEST



See Figure 9



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Fig. Fig. 9: Checking the input voltage-1981 Pick-up

  1. Place the ignition switch in the ON position.
  2.  
  3. Using a suitable voltmeter, measure the voltage between the positive (+) terminal of the coil and a ground.
  4.  
  5. The standard voltage should be approximately 12 volts. If the voltage is not within specification, check the wiring and connectors. As long as the wiring and connectors are OK, replace the coil if testing deems it to be defective.
  6.  

 
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