This tutorial explains how to do and interpret a fuel injector resistance test on 2.6L equipped Isuzu Pickup (Amigo and Rodeo).
Why a resistance test? Well, because when a fuel injector fails, it's usually due to the fact that its internal coil's windings have shorted together or have an open).
For you and I, this means that we can use a multimeter (in Ohms mode) to check the fuel injector's resistance and find 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.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar Los Inyectores (2.6L Isuzu Pick Up, Amigo, Rodeo) (at: autotecnico-online.com).
Symptoms Of A Bad Fuel Injector
Fuel injectors can fail in one of several ways. Here are some of the most basic types of fuel injector failures:
- The fuel injector's internal winding suffers an open-circuit or short-circuit problem. This causes the fuel injector to stop injecting fuel.
- The fuel injector becomes clogged and doesn't spray correctly or not enough fuel.
- It comes ON and does not turn OFF (due to electrical issues). In other words: it does not pulse ON and OFF but stays on all of the time spraying a tremendous amount of fuel as soon as you turn the ignition key to the ON position.
No matter how the fuel injector fails, the symptoms are pretty much the same ones. These symptoms are:
- Rough idle.
- Lack of power.
- Hesitation when you accelerate your 2.6L Isuzu Pickup (2.6L Amigo and 2.6L Rodeo) down the road.
- Misfire trouble codes (OBD II equipped 2.6L Rodeo only):
- P0300: Random Cylinder Misfire.
- P0301: Cylinder #1 Misfire.
- P0302: Cylinder #2 Misfire.
- P0303: Cylinder #3 Misfire.
- P0304: Cylinder #4 Misfire.
The focus of this tutorial is to see if the fuel injector's internal coil has failed (and thus causing the fuel injector to stop injecting fuel) but testing for a clogged injector isn't that much more complicated and I'll show you how in the next page.
Checking The Injector's Internal Resistance
To find out if any one of the fuel injectors in your Isuzu are fried, we're gonna' check the resistance of their internal coil winding.
If the fuel injector is bad, this coil winding will have a short or an open.
As mentioned at the beginning, this is a very easy test that can be accomplished with a simple multimeter. The multimeter will be set to its Ohms (Ω) mode to check the injector's resistance.
By the way, the instructions below call for testing all 4 fuel injectors on your 2.6L equipped Isuzu Amigo (Rodeo, Trooper).
IMPORTANT: You may need to remove the throttle body to access the fuel injectors. Follow the recommended remove and replace procedure in the repair manual to avoid complications.
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:
Disconnect the fuel injectors from their harness connectors.
NOTE: To identify which cylinder the fuel injector belongs to, see the above illustration with the cylinder # id for the 2.6L Isuzu.
Set your multimeter to Ohms (Ω) mode and:
Measure the resistance of the fuel injector across its two male spade terminals with the multimeter test leads (see the illustration above).
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.
Repeat steps 1 through 3 on the remaining fuel injectors.
NOTE: The 2.6L Isuzu fuel injector factory manual resistance specification is: 13.8 Ohms.
Let's find out what your specific multimeter test results mean:
CASE 1: The fuel injector resistance of all 4 was within specification (or similar). This confirms that the fuel injectors are OK. Specifically, that none are shorted or open internally.
Here's why: If any one of the fuel injectors were shorted or open internally, the fuel injector would have registered a radically different resistance value on your multimeter. Since the resistance values for a 4 were uniform then this test result tells you that they are not defective.
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.