I think you'll be quite surprised at how easy it is to diagnose the fuel pump as good or bad.
And the cool thing is that you don't need expensive diagnostic equipment for the fuel pump pressure test.
In this tutorial, I'll explain how to use a fuel pump pressure gauge to quickly determine if the fuel pump is good or bad.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar La Bomba De Combustible (1995-1997 2.3L Ford Ranger And Mazda B2300) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.3L Ford Ranger: 1995, 1996, 1997.
- 2.3L Mazda B2300: 1995, 1996, 1997.
NOTE: The following tutorial will help you test the fuel pressure on the 1990-1994 2.3L Ford Ranger (Mazda B2300):
Symptoms Of A Bad Fuel Pump
As you already know, the job of the fuel pump is to deliver the fuel that the engine needs to start and run.
Eventually, the fuel pump will fail and when it does, it usually causes one of the following problems:
- An engine no-start problem.
- An engine performance 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.
- Lack of power when accelerating the engine under load.
- The check engine light illuminated by lean air/fuel mixture diagnostic trouble codes.
Whether the fuel pump is causing an engine no-start problem or an engine performance issue, a fuel pump pressure test will help you determine the cause the problem.
Where To Buy A Fuel Pressure Test Gauge
You'll need a fuel pressure tester with the Ford Schrader valve adapter to test the fuel pressure on your 2.3L Ford Ranger (Mazda B2300). Here are my recommendations:
Fuel Pump Pressure Specification
| Ford | ||
|---|---|---|
| Year/Engine/Model | KOEO | KOER |
| 1995-1997 2.3L Ranger | 35-45 PSI | 30-45 PSI |
| Mazda | ||
|---|---|---|
| Year/Engine/Model | KOEO | KOER |
| 1995-1997 2.3L B2300 | 35-45 PSI | 30-45 PSI |
KOEO = Key On Engine Off.
KOER = Key On Engine Running.
Using A Fuel Pump Pressure Tester To Test The Fuel Pump
Testing the fuel pump with a fuel pressure gauge is the most accurate way to find out if the fuel pump is good or bad.
Fortunately, the fuel injector rail is equipped with a Schrader valve; to which we will connect the fuel pressure gauge.
If the fuel pump is working properly, your fuel pressure gauge should show the fuel pressure within the specified specification.
If the fuel pump is defective, the fuel pressure that the fuel pressure tester registers will not be within specification.
IMPORTANT: If the engine does not start, check the fuel pump inertia switch and reset it if necessary. A fuel pump inertia switch which has been activated by a vehicle impact (or even just hitting the curb) will cut power to the fuel pump and cause an engine no-start problem. You can find out more about it and its location here: Fuel Pump Inertia Switch Commonly Asked Questions (1989-1997 2.3L Ford Ranger).
These are the test steps:
- 1
Remove the plastic dust cap from the Schrader valve.
- 2
Place a shop towel around the Schrader valve.
The shop towel's job is to absorb any fuel that may leak when doing the next step. - 3
Connect the fuel pressure test gauge to the Schrader valve.
- 4
When ready, ask your helper to cycle the key ON and OFF but don't crank the engine while you observe the fuel pressure tester's gauge.
Check your connections for fuel leaks. Resolve any fuel leaks before continuing to the next step. - 5
Crank the engine and check the fuel pressure gauge.
- 6
Your fuel pressure gauge should register the specified fuel pressure.
Let's interpret your test result:
CASE 1: The fuel pressure gauge read 0 PSI. This confirms that the engine's no-start problem is caused by 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 specified fuel pressure specification. This test result lets you know that the fuel pump is working properly.
You can conclude that the fuel pump is fine and is not behind the engine's no-start problem.
CASE 3: The fuel pressure gauge has registered a fuel pressure well below specification. This test result indicates that the fuel pump is defective.
