How To Test The Fuel Injectors (3.2L Isuzu Amigo, Rodeo, Trooper)

Checking if a fuel injector has failed and causing your 3.2L Isuzu to misfire or suffer a rough idle is not difficult.

When a fuel injector fails, it's usually because its internal coil winding has a short-circuit problem or an open-circuit problem.

For you and me, this means that we can use a multimeter (in Ohms mode) to check the injector's resistance and figure out if it's bad (or not).

The fuel injectors have a factory resistance specification and in this tutorial, I'll show you how to test them.

You can find this tutorial in Spanish here: Cómo Probar Los Inyectores De Combustible (3.2L Isuzu Amigo, Rodeo, Trooper) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.2L Isuzu Amigo: 1999, 2000.
• 3.2L Isuzu Rodeo: 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003.
• 3.2L Isuzu Trooper: 1992, 1993, 1994, 1995, 1996, 1997.
• 3.2L Honda Passport: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002.

Symptoms Of A Bad Fuel Injector

Fuel injectors can fail in a number of ways. Here are some of the most basic types of fuel injector failure:

1. The fuel injector's internal winding suffers a short-circuit problem or an open-circuit problem. This causes the fuel injector to stop injecting fuel.
2. The fuel injector is clogged and does not inject properly or not enough fuel.
3. The fuel injector turns on and doesn't turn off (due to electrical issues). In other words, it doesn't pulse ON and OFF, it stays on all the time and sprays a tremendous amount of fuel as soon as you turn the ignition key to the ON position.

The symptoms of a failed fuel injector are pretty much the same ones no matter how it fails. These symptoms are:

• Rough idle.
• Lack of power.
• Hesitation when you accelerate your 3.2L Isuzu Amigo (Rodeo, Trooper or Honda Passport) down the road.
• Misfire trouble codes (OBD II equipped only):
  • P0300: Random Cylinder Misfire.
  • P0301: Cylinder #1 Misfire.
  • P0302: Cylinder #2 Misfire.
  • P0303: Cylinder #3 Misfire.
  • P0304: Cylinder #4 Misfire.
  • P0305: Cylinder #5 Misfire.
  • P0306: Cylinder #6 Misfire.

The focus of this tutorial is to see if the fuel injector's internal coil has failed (thus causing the injector to stop injecting fuel), but testing for a clogged injector isn't much more complicated and I'll show you how in the next page.

Where To Buy The Fuel Injector And Save

Check out the following links and comparison shop the fuel injector on your 3.2L Isuzu Amigo, Rodeo or Trooper (Honda Passport):

NOTE: Not sure if the above fuel injectors fit your particular 3.2L Isuzu (Honda Passport)? Don't worry. Once you click on the links and arrive on the site, they'll make sure it fits! If it doesn't, they'll find you the right one.

Checking The Injector's Internal Resistance

To find out if one of the injectors has fried in your Isuzu, we'll check the internal coil winding resistances of all six fuel injectors.

If a fuel injector is bad, its coil winding will have an open-circuit or a short-circuit problem.

As mentioned at the beginning, this is a very easy test that can be accomplished with a simple multimeter (set to Ohms mode).

By the way, the following instructions call for testing all six fuel injectors on your 3.2L V6 equipped Isuzu Amigo (Rodeo, Trooper).

IMPORTANT: On the 1993 to 1997 Isuzu SOHC 3.2L engines, the upper intake manifold plenum must be removed to access the fuel injectors. If your specific 3.2L Isuzu falls into this category, take a look at the following section: Fuel Injectors Under The Intake Manifold Plenum.

NOTE: Don't have a multimeter or need to upgrade yours? Check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing.

Alright, here are the steps:

1. 1

   Disconnect the fuel injectors from their harness connectors.
   
   NOTE: To identify which cylinder the fuel injector belongs to, see the cylinder ID illustration above.

2. 2

   Set your multimeter to Ohms (Ω) mode.

3. 3

   Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads (see the illustration above).

4. 4

   Write down the resistance value that your multimeter records for the specific fuel injector you're testing.
   
   The illustration above will help you identify the cylinder # the fuel injector belongs to.

5. 5

   Repeat steps 3 and 4 on the remaining fuel injectors.
   
   NOTE: The Isuzu fuel injector resistance specification is: 11.8 to 12.6 Ohms.

Let's find out what your specific multimeter test results mean:

CASE 1: All fuel injectors registered the same resistance values. This confirms that the coil windings of all six injectors are OK.

Here's why: If any one of the fuel injectors were bad, your multimeter would've registered a completely different resistance value from the factory specification. Since all resistance (Ohms) values were the same, this is an indication that the fuel injectors do not have an internal electrical fault.

CASE 2: One of the fuel injectors registered a completely different resistance value. This indicates that the fuel injector is bad. Replace the fuel injector.