How To Test The Fuel Pump (1998, 1999, 2000 2.2L Chevrolet S10, GMC Sonoma, And Isuzu Hombre)

This tutorial explains how to test the fuel pump with a fuel pressure test gauge on the 1998-2000 2.2L Chevrolet S10 pickup and GMC Sonoma.

You'll also find an explanation for performing and interpreting a starting fluid test.

With your test results, you'll quickly determine if the fuel pump is causing an engine no-start or an engine driveability problem.

In Spanish You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1998-2000 2.2L Chevrolet S10, GMC Sonoma) (at:

APPLIES TO: This tutorial applies to the following vehicles:

  • 2.2L Chevrolet S10 Pickup: 1998, 1999, 2000.
  • 2.2L GMC Sonoma: 1998, 1999, 2000.
  • 2.2L Isuzu Hombre: 1998, 1999, 2000.

Symptoms Of A Bad Fuel Pump

As you're probably already aware, the 2.2L engine in your Chevrolet S10 (GMC Sonoma) needs three things to start. These three are:

  • Air (compression).
  • Fuel.
  • Spark.

It's the fuel pump's job to provide the fuel the engine needs to start and stay running.

Sooner or later, the fuel pump will wear out and fail. When it does, it'll cause one of two problems:

  • An engine no-start problem.
  • An engine performance problem.

If the fuel pump is still working but not delivering the correct amount of fuel, you'll see one or more of the following symptoms:

  • Engine takes longer than usual to start (extended cranking).
  • Engine idle is very rough.
  • Engine backfires thru' the intake manifold under load.
  • Engine starts, then dies.
  • Lack of power when accelerating the engine under load.
  • The check engine light illuminated by lean air/fuel mixture diagnostic trouble codes.

Whether the fuel pump is causing an engine no-start or an engine performance problem, a simple fuel pump pressure test will help you diagnose the issue.

Where To Buy A Fuel Pressure Test Gauge

You'll need a fuel pressure test gauge with the GM Schrader valve adapter to test the fuel pressure on your 2.2L Chevy S10 pickup (GMC Sonoma). Here are my recommendations:

Using A Fuel Pump Pressure Tester To Test The Fuel Pump

What makes connecting a fuel pressure test gauge to the fuel system a simple affair is the Schrader valve's location on the fuel rail inlet fuel line.

In photos 2 and 3 in the image viewer above, the orange arrow points to the location of the Schrader valve on the fuel injector inlet fuel line.

Once you've connected the fuel pressure test gauge to the Schrader valve, you'll check the fuel pump's pressure output with the engine cranking (or running).

The fuel pump pressure specification for the 1998-2000 2.2L Chevrolet S10 pickup and GMC Sonoma is:

  • 41-47 PSI Key On With Engine Off.
  • With Key On Engine Running, fuel pressure should drop 3 to 10 PSI.

OK, these are the test steps:

  1. 1

    Remove the plastic dust cap from the Schrader valve.

  2. 2

    Place a shop towel around the Schrader valve.

    The shop towel's job is to absorb any fuel that may leak when doing step 2.

  3. 3

    Connect the fuel pressure test 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 while you observe the fuel pressure tester's gauge.

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

  5. 5

    Crank the engine and check the fuel pressure gauge.

  6. 6

    Your fuel pressure gauge should register the specified fuel pressure.

Let's interpret your test result:

CASE 1: The fuel pressure test gauge registered 0 PSI. This confirms that the no-start problem is caused by a lack of fuel.

This usually means that the fuel pump is bad and needs to be replaced.

CASE 2: The fuel pressure gauge registered the indicated fuel pressure specification. This fuel pressure gauge result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. You can conclude the fuel pump is OK and not behind the no-start problem.

CASE 3: The fuel pressure gauge registered a fuel pressure way below the specification. This test result lets you know that the fuel pump is failing.

Chevrolet Vehicles:

  • S10 Pickup 2.2L
    • 1998, 1999, 2000

GMC Vehicles:

  • Sonoma 2.2L
    • 1998, 1999, 2000

Isuzu Vehicles:

  • Hombre 2.2L
    • 1998, 1999, 2000