In this tutorial I'm going to show you how to test the fuel pump on the 2004, 2005, 2006, 2007, and 2008 3.5L Chevrolet Malibu and 2005, 2006, 2007, 2008 3.5L Pontiac G6. You'll be able to find out if the fuel pump is defective (or not).
Testing the fuel pump is a piece of cake because the Chevrolet Malibu (Pontiac G6) comes equipped with a Schrader valve on the fuel injector rail. This valve allows a fuel pressure test gauge to be connected to the fuel system so that you and I can check the fuel pump's output pressure.
Contents of this tutorial at a glance:
APPLIES TO: This tutorial applies to the following vehicles:
- 3.5L V6 Chevrolet Malibu: 2004, 2005, 2006, 2007, 2008.
- 3.5L V6 Pontiac G6: 2005, 2006, 2007, 2008.
You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (2004-2008 3.5L Chevrolet Malibu Y Pontiac G6) (at: autotecnico-online.com).
NOTE: You can find the fuel pump circuit wiring diagram, for the 2004-2005 3.5L Chevrolet Malibu here: Fuel Pump Wiring Diagram (2004-2005 3.5L Malibu).
Symptoms Of A Bad Fuel Pump
For the most part, fuel pump failures fall into one of two categories. The most common is where the fuel pump fails completely and it stops sending fuel to the fuel injectors. The end result is an engine that cranks but does not start.
In the second category of failures, the fuel pump continues to operate but does not send enough fuel for the engine to run optimally.
When this happens, the engine will start and run but it'll run with a few drivability issues. You'll see one or more of the following problems:
- Rough idle.
- Engine takes a long time to start (extended cranking time).
- Lack of power when accelerating the vehicle down the road.
- Engine backfires through the intake manifold when accelerating the vehicle down the road.
- Lean air fuel mixture trouble code: P0171: Fuel System Too Lean.
With this information under our belts, let's get testing.
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
The most accurate way to test the fuel pump on your 3.5L Chevy Malibu (Pontiac G6) is to use a fuel pump pressure tester.
This fuel pump pressure tester is connected to the Schrader valve (see photo above) which is located on the fuel injector rail. To be a bit more specific, it's located near the alternator and above fuel injector for cylinder #1.
NOTE: If you don't have a fuel pressure test gauge, you can run down to your local auto parts store and buy one there. You can also buy one online. Check out my recommendations here: Where To Buy A Fuel Pressure Test Gauge.
FUEL PRESSURE SPECIFICATION:
2004-2005 3.5L Malibu: 50-60 PSI with the key on engine off (KOEO) or key on engine running (KOER).
2006 3.5L Malibu: 55-60 PSI with the key on engine off (KOEO) or key on engine running (KOER).
2007-2008 3.5L Malibu: 56-62 PSI with the key on engine off (KOEO) or key on engine running (KOER).
These are the test steps:
Place a shop towel around the Schrader valve.
Connect a fuel pressure gauge to the Schrader valve on the fuel rail.
When ready have your helper crank the engine while you observe the fuel pressure tester gauge.
The fuel pressure tester should register:
2004-2005 3.5L Malibu: 50-60 PSI.
2006 3.5L Malibu: 55-60 PSI.
2007-2008 3.5L Malibu: 56-62 PSI.
Let's examine your test results:
CASE 1: The fuel pressure gauge registered 0 PSI. This test result lets you know that the fuel pump is not supplying fuel to the engine. Without fuel, the engine is not going to start.
If your Chevy Malibu (Pontiac G6) is cranking but not starting, then you can conclude that the reason behind this is a defective fuel pump.
CASE 2: The fuel pump registered a pressure way below the specified range but not 0 PSI. This lets you know that the fuel pump is defective.
If the fuel pump is not supplying enough fuel to the engine, the engine may start and run but it'll run badly. In these cases you'll see one or more of the following:
- The engine will start and run but as soon as your put the transmission in Drive and accelerate, the engine stalls.
- The engine starts and runs, but you hear explosions coming from the intake manifold when you accelerate the engine.
- Lean air/fuel mixture trouble codes lighting up the check engine light.
CASE 3: The fuel pump registered a pressure within the specified range. This lets you know that the fuel pump is working within normal parameters. In other words, it's not defective.
If your 3.5L Chevy Malibu (Pontiac G6) is cranking but not starting, you can conclude that it's not due to a defective fuel pump.