How To Test The Fuel Pump (1998-2000 2.2L Chevrolet S10, GMC Sonoma)

Using Starting Fluid

Spraying starting fluid down the throttle body and then cranking the engine to see if it starts has been my go-to test when troubleshooting an engine no-start problem.

Although it's not the most accurate way of diagnosing a bad fuel pump, it gets my troubleshooting efforts pointed in the right direction. I think it'll help you too.

IMPORTANT: The accuracy of the starting fluid test depends on having all four spark plugs delivering spark to their cylinders. If you haven't checked the spark plug wires for spark (with a dedicated spark tester), you need to do so before starting the test. Otherwise, you may get a false-positive result from this test.

These are the test steps:

1. 1

   Remove the intake air duct from the throttle body.
   
   You don't have to completely remove it, since you'll have to reconnect it in one of the next steps.

2. 2

   Open the throttle manually, and spray starting fluid down the bore.
   
   When you have sprayed a good squirt of starting fluid, quickly reconnect the air duct to the throttle body (you don't have to tighten the hose clamp).
   
   Reconnecting the intake air duct is a very important safety precaution in case you get a back-fire thru' the intake manifold.

3. 3

   Crank the engine once the intake air duct is back on the throttle body.

4. 4

   You'll get one of two results:
   
   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 analyze your test result:

CASE 1: The engine started and ran for a few seconds. This result confirms that the engine's no-start problem is caused by a lack of fuel.

I suggest that your next step be to test the fuel pump's fuel pressure with a test gauge. For this test go to: Using A Fuel Pump Pressure Tester To Test The Fuel Pump.

CASE 2: The engine did not start, not even momentarily. This result generally tells you a lack of fuel IS NOT the reason your car is not starting.

Now, remember what I said about this test not being very accurate? Well, I suggest you do one more test and this is to test the fuel pump's fuel pressure with a test gauge. For this test go to: Using A Fuel Pump Pressure Tester To Test The Fuel Pump.