What makes testing the fuel pump so easy, on the 3.1L V6 equipped Buick Regal or Oldsmobile Cutlass Supreme is that the fuel injector rail is fitted with a Schrader valve.
We can connect a fuel pressure gauge to the Schrader valve to check the fuel pump pressure.
In this tutorial, I'll walk you through the process of testing the fuel pump using a fuel pressure tester. I've also included instructions on how to test an engine no-start problem with starting fluid.
Contents of this tutorial:
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You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1989-1993 3.1L Buick Regal, Oldsmobile Cutlass Supreme) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 3.1L Buick Regal: 1989, 1990, 1991, 1992, 1993.
- 3.1L Oldsmobile Cutlass Supreme: 1989, 1990, 1991, 1992, 1993.
ENGINE NO-START DIAGNOSTICS: The following guide is a good engine no-start troubleshooting resource:
Symptoms Of A Bad Fuel Pump
It's the job of the fuel pump to deliver fuel to the injectors when you turn the key to start and crank the engine.
Once the engine starts, the fuel pump continues to deliver fuel to the fuel injectors (until the engine stops).
When the fuel pump fails, it usually causes one of the following problems:
- An engine no-start problem.
- A driveability problem.
If the fuel pump is still working but not delivering 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.
Both can be diagnosed with a simple fuel pump pressure test.
NOTE: If the fuel pump is OK (not behind the engine no-start), the following guide is a good resource that'll help you get to the bottom of the issue:
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:
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Using A Fuel Pump Pressure Tester To Test The Fuel Pump
We'll connect the fuel pressure gauge to the Schrader valve on the fuel injector rail (photo 2 of 2 shows the location of the Schrader valve).
You'll need the special GM Schrader valve adapter to connect your fuel pressure gauge to the Schrader valve.
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 1989-1993 3.1L V6 Buick Regal and Oldsmobile Cutlass Supreme vehicles:
- 40-47 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
Remove the plastic dust cap from the Schrader valve.
- 2
Connect your fuel pressure tester to the Schrader valve.
- 3
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. - 4
Have your helper crank the engine while you observe the needle on the fuel pressure tester gauge.
- 5
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.
Using Starting Fluid
I've used the starting fluid test fairly frequently over the years to diagnose engine no-start problems.
Although the test isn't as accurate as the fuel pressure test, the starting fluid test will still point your engine no-start diagnostic in the right direction.
IMPORTANT: To get the most accurate test result from the starting fluid test, you must ensure that all of the spark plug wires are sparking before beginning the test. Test all 6 spark plug wires for spark with a dedicated spark tester if you haven't already done so.
OK, these are the test steps:
- 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 or.
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 isn't starting due to 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.
If this info saved the day, buy me a beer!
