I think you'll be surprised at how easy it is to troubleshoot the fuel pump on your 3.1L V6 Chevrolet or 3.1L V6 Pontiac vehicle as good or bad.
In this tutorial, you'll find the fuel pump pressure test explained step by step. With your test results, you'll quickly determine whether the fuel pump is good or bad.
I'll also explain how to do the starting fluid test. The starting fluid test will help you diagnose an engine no-start problem caused by a lack of fuel.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1989-1994 3.1L V6 Chevrolet y Pontiac) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L Chevrolet Beretta: 1990, 1991, 1992, 1993.
- 3.1L Chevrolet Cavalier: 1990, 1991, 1992, 1993, 1994.
- 3.1L Chevrolet Celebrity: 1990.
- 3.1L Chevrolet Corsica: 1990, 1991, 1992, 1993.
- 3.1L Chevrolet Lumina: 1990, 1991, 1992, 1993, 1994.
- 3.1L Pontiac 6000: 1989, 1990, 1991.
- 3.1L Pontiac Grand Prix: 1989, 1990, 1991, 1992, 1993.
- 3.1L Pontiac Sunbird: 1991, 1992, 1993, 1994.
Symptoms Of A Bad Fuel Pump
When the fuel pump fails, it'll fail in one of two flavors:
- The fuel pump will cause an engine no-start problem.
- The fuel pump will cause an engine performance problem.
If the fuel pump is allowing the engine to start but isn't sending enough fuel, 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.
Both can be diagnosed with a simple fuel pump pressure test.
Where To Buy A Fuel Pressure Test Gauge
You'll need a fuel pressure test gauge with the GM Schrader valve adapter to test the fuel pressure on your 3.1L V6 Buick or Oldsmobile. Here are my recommendations:
Using A Fuel Pump Pressure Tester To Test The Fuel Pump
What makes testing the fuel pump easy is the fact that GM put a Schrader valve on the injector rail.
This Schrader valve allows us to connect a fuel pressure gauge (to it) and check the fuel pump pressure output.
If the fuel pump is bad, your fuel pressure reading will be at 0 PSI or below the factory specification.
If you don't have a fuel pressure tester with the correct adapter, take a look at this section: Where To Buy A Fuel Pressure Test Gauge.
The fuel pump pressure specification for the 1989-1994 3.1L V6 Chevy and Pontiac vehicles is:
- 40-47 PSI Key On With Engine Off.
- With Key On Engine Running, fuel pressure should drop 3 to 10 PSI.
Alright, let's get started:
Remove the plastic dust cap from the Schrader valve.
Connect your fuel pressure tester to the Schrader valve.
When ready, ask your helper to cycle the key ON and OFF but not crank the engine while you check your test gauge connection for fuel leaks.
If any fuel leaks are present, resolve them before continuing to the next step.
Have your helper crank the engine while you observe the needle on the fuel pressure tester gauge.
Your fuel pressure gauge should register the specified fuel pressure..
Let's take a look at your fuel pressure test results:
CASE 1: The fuel pressure test gauge registered 0 PSI. This confirms that the no-start problem is caused by a lack of fuel.
This usually means that the fuel pump is bad and needs to be replaced.
CASE 2: The fuel pressure gauge registered the indicated fuel pressure specification. This fuel pressure gauge result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. You can conclude the fuel pump is OK and not behind the no-start problem.
CASE 3: The fuel pressure gauge registered a fuel pressure way below the specification. This test result lets you know that the fuel pump is failing.