How To Test The Fuel Pump (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma)

The Starting Fluid Test

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

The cool thing about the throttle body fuel injection system is that you can see whether or not the injectors are injecting fuel into the intake manifold.

The other benefit of this system is that when fuel is not being injected you can simply spray starting fluid into the throttle body bores and then crank the engine and see if the engine starts.

If only fuel injection is missing, the engine will start and run until the starting liquid you sprayed is consumed.

Although this is not the most accurate way to test the fuel pump, it will point your engine no-start diagnostic in the right direction.

IMPORTANT: If you haven't checked all six spark plug wires for spark yet, please do so before performing the starting fluid test. I recommend using a dedicated spark tester for the spark test.

OK, these are the test steps:

  1. 1

    Remove the cover from the air cleaner assembly.

    You don't have remove the air cleaner assembly from the engine (best to leave it in place).

  2. 2

    Open the throttle manually, and spray starting fluid down the bore.

  3. 3

    When you have sprayed a good squirt of starting fluid, quickly install the air cleaner assembly's cover (you don't have to tighten the nut).

    Reinstalling the air cleaner assembly's top is a very important safety precaution in case you get a back-fire thru' the intake manifold.

  4. 4

    Crank the engine once you've place the cover back on the air cleaner assembly.

  5. 5

    You'll get one of two results with this test:

    1.) The engine will start momentarily and after a few seconds will die.

    2.) The engine will only crank but not start at all.

OK, let's interpret your test results:

CASE 1: The engine started and ran for a few seconds. This test result confirms that the engine isn't starting due to a lack of fuel.

The most likely cause of this lack of fuel is a bad fuel pump.

CASE 2: The engine did not start, not even momentarily. This test result tells you that the engine's no-start problem IS NOT due to a lack of fuel.

It's important to note that this the accuracy of this test result depends on having all six spark plug wires sparking.

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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