How To Test The Fuel Pump (1992, 1993, 1994, 1995 4.3L V6 CPI Chevrolet S10 Pickup And GMC Sonoma)

In this tutorial, I'll explain the fuel pump pressure test step by step on the 1992-1995 Chevrolet S10 pickup or GMC Sonoma equipped with the 4.3L V6 CPI fuel injected engine.

You'll quickly determine if a fuel pump issue is causing an engine no-start or performance problem.

I'm also explaining how to use starting fluid to determine if the engine's no-start problem is due to a lack of fuel.

NOTE: CPI = Central Port Injection.

In Spanish You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1992-1995 4.3L CPI Chevrolet S10 Pickup, GMC Sonoma) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

  • 4.3L V6 CPI Chevrolet S10 Pickup: 1992, 1993, 1994, 1995.
  • 4.3L V6 CPI GMC Sonoma: 1992, 1993, 1994, 1995.

NOTE: The following fuel pressure test tutorials may come in handy:

Symptoms Of A Bad Fuel Pump

The fuel pump, which is located inside the fuel tank, will fail sooner or later and generally cause one of two problems:

  • An engine no-start problem.
  • An engine performance problem (the engine starts and runs, but runs badly).

When the fuel pump supplies barely enough fuel to start the engine, 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 vehicle under load.

A fuel pump pressure test will help you determine if a fuel pump failure is causing an engine no-start or an engine performance problem.

Where To Buy A Fuel Pressure Test Gauge

The Actron CP7838 Professional Fuel Pressure Tester is my go-to tester for three reasons:

  • Its a quality tool (not some cheap knock-off tool that'll only last one use).
  • It fits the GM Schrader valve.
  • It doesn't cost an arm and a leg.

You can buy it here: Actron CP7838 Professional Fuel Pressure Tester (at amazon.com).

Fuel Pump Pressure Specification

Chevrolet
Year/Engine/Model KOEO KOER
1992-1995 4.3L CPI S10 Pickup 55-61 PSI 3 to 10 PSI drop w/ KOER
GMC
Year/Engine/Model KOEO KOER
1992-1995 4.3L CPI Sonoma Pickup 55-61 PSI 3 to 10 PSI drop w/ KOER

KOEO = Key On Engine Off.

KOER = Key On Engine Running.

CPI = Central Port Injection.

Using A Fuel Pump Pressure Tester To Test The Fuel Pump

The fuel pump pressure test consists of connecting a fuel pressure gauge to the Schrader valve and then cranking the engine.

If the fuel pump is OK, your fuel pressure tester should indicate the specified fuel pressure. If the fuel pump is bad, you'll usually see one of two things:

  • A fuel pressure of 0 PSI.
  • A fuel pressure below the specified value.

To describe the location of the Schrader valve in a little more detail, it's located on the fuel pressure line that enters the left side of the intake manifold manifold. The orange arrow in photo 1 of 2 above points to the general location of the Schrader valve.

NOTE: If you don't have a fuel pressure tester with the correct adapter, see my recommendations here: Where To Buy A Fuel Pressure Test Gauge.

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 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 interpret your test results:

CASE 1: The fuel pressure test gauge registered 0 PSI. This test result confirms that a lack of fuel from the fuel pump is causing the engine to not start.

This test result usually confirms that the fuel pump has failed and needs to be replaced. When replacing the fuel pump, you'll also need to replace the fuel pump strainer and the fuel filter.

CASE 2: The fuel pressure gauge registered the indicated fuel pressure specification. This test result tells you that the fuel pump is functioning correctly and sending fuel to the fuel injectors.

If the engine isn't starting, You can conclude that the fuel pump IS NOT behind the issue.

CASE 3: The fuel pressure gauge registered a fuel pressure way below the specification. This test result tells you that the fuel pump is failing. Replace the fuel pump, the fuel pump strainer, and the fuel filter.

Chevrolet Vehicles:

  • S10 Pickup 4.3L
    • 1992, 1993, 1994, 1995

GMC Vehicles:

  • Sonoma 4.3L
    • 1992, 1993, 1994, 1995