How To Test The Fuel Pump (1988, 1989, 1990, 1991, 1992, 1993 2.8L V6 TBI Chevrolet S10 Pickup, GMC S15 Pickup, And GMC Sonoma)

The fuel pump can be easily tested with a fuel pressure tester on your 2.8L Chevrolet S10 pickup. In this tutorial, you'll find the step-by-step instructions that explain how to connect a fuel pressure test gauge to the fuel system and check the fuel pump pressure.

I'm also including a section on using starting fluid to determine if the engine won't start due to lack of fuel.

APPLIES TO: This tutorial applies to the following vehicles:

  • 2.8L Chevrolet S10 Pickup: 1988, 1989, 1990, 1991, 1992, 1993.
  • 2.8L GMC S15 Pickup: 1988, 1989, 1990.
  • 2.8L GMC Sonoma: 1991, 1992, 1993.

Symptoms Of A Bad Fuel Pump

You would think that a bad fuel pump would simply stop working and the engine would not start until it was replaced.

Unfortunately, a fuel pump can fail but provide just enough fuel to start the engine but not enough to keep it running optimally. To reiterate this point, the fuel pump can fail in two ways:

  • 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 two reasons: Its quality and its brand name (it's not some cheap knock-off tool that'll only last one use). You can buy it here: Actron CP7838 Professional Fuel Pressure Tester (at

Fuel Pump Pressure Specification

Year/Engine/Model KOEO KOER
1988-1993 2.8L TBI S10 Pickup 9-13 PSI 9-13 PSI
Year/Engine/Model KOEO KOER
1988-1993 2.8L TBI S15 Pickup, Sonoma 9-13 PSI 9-13 PSI

KOEO = Key On Engine Off.

KOER = Key On Engine Running.

Using A Fuel Pump Pressure Tester To Test The Fuel Pump

In order to check the fuel pump pressure, a special adapter must be installed between the fuel filter and the fuel line that connects to the throttle body.

As you can see in the illustrations in the image viewer above, the adapter is connected to the outlet side of the fuel filter.

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, let's get testing:

  1. 1

    Place a shop towel under the fuel filter. The shop towel's job is to absorb any fuel that may leak when doing the next step.

  2. 2

    Disconnect the fuel line from the fuel filter.

    NOTE: You need to disconnect the fuel line on the engine side of the fuel filter.

  3. 3

    Connect the test adapter between the fuel line and the fuel filter.

  4. 4

    Connect the fuel pressure gauge to the adapter.

  5. 5

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

  6. 6

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

  7. 7

    Crank the engine and check the fuel pressure gauge.

  8. 8

    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 2.8L
    • 1988, 1989, 1990, 1991 1992, 1993

GMC Vehicles:

  • S15 Pickup 2.8L
    • 1988, 1989, 1990
  • Sonoma 2.8L
    • 1991, 1992, 1993