In this tutorial, I'll explain how to test the fuel pump with a fuel pressure test gauge.
I've also included the instructions on how to perform a starting fluid test (which will help you confirm if an engine no-start problem is due to a lack of fuel).
All of the tests are explained in detail so that you find out if the fuel pump is bad or not.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L V6 Buick Century: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.
- 3.1L V6 Buick Regal: 1994, 1995, 1996.
- 3.1L V6 Buick Skylark: 1994, 1995, 1996.
- 3.1L V6 Oldsmobile Achieva: 1994, 1995, 1996, 1997, 1998.
- 3.1L V6 Oldsmobile Cutlass: 1997, 1998, 1999.
- 3.1L V6 Oldsmobile Cutlass Ciera: 1994, 1995, 1996.
- 3.1L V6 Oldsmobile Cutlass Supreme: 1993, 1994, 1995, 1996, 1997.
ENGINE NO-START DIAGNOSTICS:
Symptoms Of A Bad Fuel Pump
For the most part, when a fuel pump fails, it'll cause one of two problems:
- Either the engine will not start
- - or -
- The engine starts and runs, but runs very badly.
If the fuel pump still functions, but doesn't send the correct amount of 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.
If these conditions are being caused by a bad fuel pump, a simple fuel pump pressure test will let you know.
If you're troubleshooting an engine no-start problem, this guide is a good resource:
Where To Buy A Fuel Pressure Test Gauge
You'll need a fuel pressure test gauge and the correct adapter to test the fuel pump pressure on your vehicle.
The following kits include the adapter you need to connect the fuel pressure gauge to the Schrader valve:
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Using A Fuel Pump Pressure Tester To Test The Fuel Pump
The fuel injector rail, on your vehicle's engine comes equipped with a Schrader valve.
It's to this Schrader valve that we're going to connect the fuel pressure tester gauge via an adapter.
The Schrader valve is located on the side of the engine facing the serpentine drive belt, beside the power steering pump reservoir.
The orange arrow in the photo above points to the Schrader valve.
NOTE: 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 for the 1993-1999 3.1L V6 Buick and Oldsmobile vehicles is:
- 40-47 PSI Key On With Engine Off.
- With Key On Engine Running, fuel pressure should drop 3 to 10 PSI.
The fuel pump pressure for the 2000 3.1L V6 Buick Century is:
- 48-55 PSI Key On With Engine Off.
- With Key On Engine Running, fuel pressure should drop 3 to 10 PSI.
The fuel pump pressure for the 2001-2005 3.1L V6 Buick Century is:
- 52-59 PSI Key On With Engine Off.
- With Key On Engine Running, fuel pressure should drop 3 to 10 PSI.
OK, these are the test steps:
- 1
Place a shop towel under the Schrader valve. The shop towel's job is to absorb any fuel that may leak when doing step 2.
- 2
Connect the fuel pressure gauge to the Schrader valve.
Most fuel pressure gauges can be connected to the Schrader valve without an adapter. If yours isn't one of them, connect the correct adapter to the Schrader valve and then connect the gauge to it. - 3
When ready, ask your helper to cycle the key on and off but don't crank the engine while checking for fuel leaks.
If no fuel leaks, go to next step.
If fuel is leaking, resolve the leak before continuing to the next step. - 4
Crank the engine and observe the fuel pressure gauge.
- 5
The 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 test result confirms that the engine is not starting due to a lack of fuel.
You can conclude that the fuel pump is not functioning and is the cause of the engine's no-start problem.
CASE 2: The fuel pressure gauge registered the indicated fuel pressure specification. This is the correct and expected test result and it confirms that the fuel pump is OK.
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. Replace the fuel pump.
Using Starting Fluid
The starting fluid test is a pretty simple way of checking to see if the engine is not starting due to a lack of fuel (like when the fuel pump stops working).
This test is usually the first test I perform when diagnosing a no-start problem.
Although the starting fluid test is not the most accurate way of diagnosing a bad fuel pump, it will get your no-start diagnostic pointing in the right direction.
IMPORTANT: To get the most accurate test result from this test you need to first make sure that all 6 spark plug wires are sparking. If you haven't already, test all 6 spark plug wires for spark with a dedicated spark tester.
OK, this is what you'll need to do:
- 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
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
Crank the engine once the intake air duct is back on the throttle body.
- 4
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 find out what your results mean:
CASE 1: If the engine started and ran for a few seconds. This test result lets you know that the engine's no-start problem is due to lack of fuel.
Now remember, this isn't the most accurate way of diagnosing a bad fuel pump. If I were in your shoes I would 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 test result most always tells you that the engine's no-start problem IS NOT due to a lack of fuel from the fuel pump.
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.
More 3.1L V6 Buick, Oldsmobile Tutorials
You can find a complete list of 3.1L V6 Buick (Oldsmobile) tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test Engine Compression Test (3.1L V6 Buick, Oldsmobile).
- How To Test A Blown Head Gasket (3.1L V6 Buick, Oldsmobile).
- How To Test The 24X Crankshaft Position Sensor (1995-1997 3.1L V6 Oldsmobile Cutlass Supreme).
- What Does The CKP Sensor Do? (3.1L V6 Buick, Oldsmobile).
If this info saved the day, buy me a beer!
