How To Test The Fuel Pump (1993-1995 3.2L Isuzu Rodeo)

Sooner or later the fuel pump will fail in your 3.2L Isuzu Rodeo and when it does, the engine will either not start or it will start and run but will run with a lack of power.

The cool thing is that testing the fuel pump is not difficult and in this tutorial, I'll explain how to test the fuel pressure produced by the fuel pump using a fuel pressure gauge.

You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1993-1995 3.2L Isuzu Rodeo) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.2L V6 Isuzu Rodeo: 1993, 1994, 1995.
• 3.2L V6 Honda Passport: 1994, 1995.

Symptoms Of A Bad Fuel Pump

Your 3.2L Isuzu Rodeo's engine needs three things to start and they are: air, fuel and spark. It's the job of the fuel pump to provide the fuel that the engine needs.

Over the years, I've found that fuel pumps typically fail in one of two ways. The most common type of failure I've seen involves the fuel pump failing completely, stopping fuel delivery to the engine. This causes the engine to crank but not start due to lack of fuel.

In the other type of failure, the fuel pump is still working, but it's delivering just enough fuel to start the engine, but not enough to keep it running optimally.

This type of fuel pump failure causes one or more of the following symptoms.

• Engine backfires when you accelerate the vehicle on the road.
• Engine take a long time to start.
• Engine knock when accelerating the vehicle on the road (due to a lean air/fuel mixture).

What makes testing the fuel pump so easy is that your 3.2L Isuzu Rodeo has a Schrader valve that we can hook up a fuel pressure gauge to and see if the fuel pump is actually delivering fuel to the injectors.

Where To Buy A Fuel Pressure Test Gauge

A fuel pressure tester is one of the most important tools any serious DIY'er should have in their tool box.

The cool thing is, you can buy a fuel pressure test gauge just about anywhere. The following fuel pressure gauge kits are pretty good deals and will help you compare prices:

All of the fuel pump pressure test kits above have the fitting that will connect to your Isuzu's Schrader valve.

TEST 1: Fuel Pressure Test (Engine Does Not Start)

If the fuel pump fails, your 3.2L V6 Rodeo (Honda Passport) will not start due to a lack of fuel at the injectors.

The cool thing is that to test the fuel pump, you simply hook up a fuel pressure tester to the Schrader valve located on the fuel rail and then crank or start the engine.

If the fuel pump is good (and not behind the engine no-start problem), you'll see a fuel pressure of 41-46 PSI on the fuel pressure gauge.

If the fuel pump is bad (thus causing the engine no-start problem) you'll see a fuel pressure of 0 PSI.

NOTE: If you don't have a fuel pressure gauge, take a look at the section: Where To Buy A Fuel Pressure Test Gauge.

OK, let's get started with this test:

1. 1

   Remove the plastic dust cap from the Schrader valve.

2. 2

   Place a shop towel around the Schrader valve and fuel line. The shop towel's job is to absorb any fuel that may leak when doing step 3.

3. 3

   Connect the fuel pressure gauge to the Schrader valve.

4. 4

   When ready, ask your helper to cycle the key ON and OFF but don't crank the engine.

5. 5

   Check your connections for fuel leaks. Resolve any fuel leaks before continuing to the next step.

6. 6

   Crank the engine and check the fuel pressure gauge.

7. 7

   Your fuel pressure gauge should register the specified fuel pressure.

Let's take a look at what your results mean:

CASE 1: The fuel pressure gauge registered 0 PSI. This confirms that the fuel pump is not functioning.

This test result usually means that the fuel pump is bad and needs to be replaced. But before you do, you need to check that the fuel pump fuse isn't blown. Go to: TEST 3: Checking The Fuel Pump Fuse.

CASE 2: The fuel pressure gauge registered 41 to 46 PSI. This is the correct and expected test result.

CASE 3: The fuel pressure gauge registered a pressure less than 41 PSI. This test result tells you that the fuel pump is failing.