The Starting Fluid Test

How To Test The Fuel Pump With Starting Fluid (1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995 4.3L V6 TBI Chevrolet S10 Pickup, GMC S15 Pickup, And GMC Sonoma)

The starting fluid test has been my go-to test for diagnosing an engine no-start problem from day one of my automotive repair career.

And when I started, most vehicles had carburetors and throttle body fuel injection systems (TBI) were just coming online.

The cool thing about using starting fluid (to diagnose an engine no-start issue) is that it let's you know right away if a lack of fuel is keeping the engine from starting.

The most important thing to remember when performing a starting fluid test is that you first need to make sure that all six spark plug wires are sparking (with a spark tester).

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 4.3L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995

GMC Vehicles:

  • S15 Pickup 4.3L
    • 1988, 1989, 1990
  • Sonoma 4.3L
    • 1991, 1992, 1993, 1994, 1995