How To Troubleshoot The Fuel Pump (GM 3.1L, 3.4L)

I'm going to show you two different methods to verify if the no start condition on your 3.1L or 3.4L GM vehicle is due to a lack of fuel, which usually means that the fuel pump has gone bad.

One method involves using just starting fluid and the other involves using a fuel pressure gauge. One method is a very accurate way of diagnosing a lack of fuel condition causing a no start. The other method is not that accurate.

I've used both methods successfully and I'll describe them in a step-by-step way in this tutorial.

IMPORTANT: Gasoline is extremely flammable. Be careful and take all necessary safety precautions. Use extreme care when using starting fluid since it ignites as easily as gasoline. Accomplishing both tests indicated in this article, without any unhappy consequences, is more than possible if you're careful and use common sense.

En Español You can find this tutorial in Spanish here: Cómo Probar La Bomba de Combustible (GM 3.1L, 3.4L) (at: autotecnico-online.com).

Symptoms Of A Bad Fuel Pump

A bad fuel pump will make your 3.1L or 3.4L Venture (or Malibu, Regal, Skylark, Corsica, Impala, Venture, etc.) crank but not start. Here are some more specific symptoms:

  1. All of the coil packs, sitting on top of the ignition control module, are creating and delivering spark to the spark plugs. So you know that the ignition system is not at fault.
  2. You've sprayed starting fluid (or carburetor spray) into the throttle body and your vehicle started, even if only momentarily.

Although the above list is a not a very complete list of symptoms, the theme that runs thru' them, and any other related symptom, is that the engine will crank and crank, but not start.

Which And Where To Buy A Fuel Pressure Gauge

Owning a fuel pressure gauge is now becoming a must. All vehicles now use an electrical fuel pump to deliver fuel (under high pressure) to the fuel injectors and the best way to diagnose this fuel pump is with a fuel pressure gauge.

As mentioned earlier (in fuel pump test 2), in all of the GM 3.1L and 3.4L V6 equipped vehicles GM was kind enough to put a Schrader valve on the fuel injector rail where you can tap into the fuel system and check its performance.

A fuel pressure gauge can cost you as little as $40 (US) or as much as $200 (US). The price difference depends on what type of fuel pressure gauge set you buy, this means either buying a non-professional technician grade tool or a professional technician grade too. Whichever one you buy, it's an investment that will pay for itself many times over.

Here are my recommendations:

NOTE: All of the kits above have the adapter for the GM Schrader valve that you'll need to test your vehicle.

FUEL PUMP TEST 1: Fuel Pressure Test With Gauge

Fuel Pump Schrader Valve Test Port Location. How To Troubleshoot The Fuel Pump (GM 3.1L, 3.4L)

Testing the fuel pressure with a fuel pressure gauge can be very easily done on your 3.1L or 3.4L Monte Carlo (Venture, Beretta, Corsica, Lumina, Monte Carlo, Grand Prix, Grand Am, Cutlass Supreme, etc.). This is due to the fact that GM has included a Schrader valve on the fuel rail to which you and I can attach a fuel pressure gauge to.

Using a fuel pressure gauge to make sure that enough fuel is reaching the fuel injectors is the most accurate way to diagnose the fuel pump in your car or mini-van.

If you don't own a fuel pressure gauge, you can rent one from your local auto parts store (AutoZone, O'Reilly Auto Parts). If you're interested in buying your own, check out my recommendations here: Which And Where To Buy A Fuel Pressure Gauge.

OK, let's get started with this test:

  1. 1

    Connect the fuel pressure gauge to the Schrader valve on the fuel rail.

    With a shop towel, mop up any fuel that was released during the process of connecting the fuel pressure test gauge.

  2. 2

    When ready, ask your helper to crank the engine a few seconds while you check for fuel leaks at the Schrader valve.

    If a fuel leak is present, resolve it before continuing to the next step.

  3. 3

    Ask your helper to crank the engine while you observe the fuel pressure tester's gauge.

  4. 4

    Your fuel pressure gauge will register one of the two following results:

    1.) The fuel pressure gauge will register 35 PSI.

    2.) The fuel pressure gauge will register 0 PSI.

OK, now that the testing part is done, let's take a look at what your results mean:

CASE 1: If the fuel pressure gauge registered 0 PSI. This confirms that the cause of your Venture's (Malibu, Impala, Lumina, Grand Am, Cutlass Supreme, etc.) is caused by a lack of fuel.

Now, I usually take one more precaution, before condemning the fuel pump as bad and this is to check that the fuel pump is getting 12 Volts as the engine is cranking. This is just to make sure that the fuel pump relay and fuse are OK and doing their job.

What you'll have to do to accomplish this is to attach a multimeter in Volts DC mode to the wire that supplies this voltage to the fuel pump and while a helper cranks the engine, verify that the fuel pump is getting this power. If the 12 Volts are being supplied to the fuel pump, then you have now 100% verified that the fuel pump is fried and needs to be replaced.

CASE 2: If the fuel pressure gauge registered 35 PSI. This fuel pressure gauge result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. The reason your 3.1L or 3.4L GM vehicle is not starting is due to another reason. The fuel pump is OK.

For more testing suggestions, I suggest you take a look at the following tutorial How To Troubleshoot A No Start (GM 3.1L, 3.4L).



Buick Vehicles:

  • Century 3.1L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Regal 3.1L
    • 1994, 1995, 1996, 1997, 1998
  • Skylark 3.1L
    • 1994, 1995, 1996, 1997, 1998

Chevrolet Vehicles:

  • Beretta 3.1L
    • 1994, 1995, 1996
  • Corsica 3.1L
    • 1994, 1995, 1996
  • Impala 3.4L
    • 2000, 2001, 2002, 2003, 2004, 2005
  • Lumina 3.1L
    • 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001

Chevrolet Vehicles:

  • Malibu 3.1L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • Monte Carlo 3.1L, 3.4L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Oldsmobile Vehicles:

  • Achieva 3.1L
    • 1995, 1996, 1997, 1998
  • Alero 3.4L
    • 1999, 2000, 2001, 2002, 2003, 2004
  • Cutlass (& Ciera) 3.1L
    • 1995, 1996, 1997, 1998, 1999
  • Cutlass Supreme 3.1L
    • 1995, 1996, 1997

Pontiac Vehicles:

  • Grand Am 3.1L, 3.4L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
  • Grand Prix 3.1L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003