Sooner or later, the fuel pump in your 3.0L equipped Ford Ranger (or Mazda B3000) is gonna' fail. And let me tell you that testing it is not hard.
In this tutorial I'll explain the two methods you can use the test to see if the fuel pump is behind your Ford's no-start condition. I'll also explain how the fuel pump pressure test can help you find out if the fuel pump is behind a lean condition causing a lack of power on your vehicle.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar La Bomba de Combustible (3.0L Ford Ranger) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- Ford 3.0L Ranger: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000.
- Mazda 3.0L B3000: 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999.
Symptoms Of A Bad Fuel Pump
The fuel pump can fail in one of two ways. The first type of failure is a complete failure in which the fuel pump stops sending fuel to the fuel injectors.
The other type of failure is a fuel pump that's working but NOT sending enough fuel to the fuel injectors and thus provoking all kinds of performance issues.
When a fuel pump completely fails, you'll see that:
- The engine turns over but will not start.
- The ignition coil pack feeding spark to all 6 cylinders.
- The PCM will still pulse (activate) all 6 fuel injectors.
- Fuel pressure PSI is 0 PSI at the Schrader valve test port.
- Engine starts, although momentarily, if you spray starting fluid into the throttle body and then crank the engine.
When the fuel pump is starting to fail and under-performing, you'll probably see one or more of the following symptoms:
- Lean air/fuel mixture trouble codes.
- Rough idle.
- Engine starts after extended cranking.
- Lack of power when accelerating the vehicle down the road.
- Back-fires thru' the intake manifold when accelerating your pickup or van down the road.
Both of these conditions can be tested with a fuel pressure gauge. Alright, with this info under our belts, let's get testing.
Where To Buy A Fuel Pressure Test Gauge
You can buy a fuel pressure test gauge just about anywhere and is one of the most important tools any serious DIY'er should have in his/her tool box.
The following fuel pressure test gauge kits are pretty good deals and include the adapter to tests all 3.0L Fords:
All of the fuel pump pressure test kits above have the fitting that will connect to your Ford's Schrader valve.
TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge
In this section we'll use a fuel pressure test gauge to find out if the fuel pump is creating the factory specified pressure.
The cool thing about using a fuel pressure test gauge, to test the fuel pump's fuel pressure, is that we can find out if the fuel pump is behind the no-start condition or behind a lean condition (if your Ford starts, runs, but runs with a lack of power).
The fuel pressure specifications with the key on engine off (KOEO) and key on engine running (KOER) are:
| Year | KOEO | KOER |
|---|---|---|
| 1992-1993 | 35-40 PSI | 30-45 PSI |
| 1994-1995 | 35-45 PSI | 28-45 PSI |
| 1996-1997 | 30-45 PSI | Not Available |
| 1998 | 56-72 PSI (Gasoline) 47-63 PSI (Flex Fuel) | Not Available |
NOTE: If you don't have a fuel pressure gauge, take a look at the section: Where To Buy A Fuel Pressure Test Gauge.
OK, let's get started with this test:
- 1
Place a shop towel around the Schrader valve. The shop towel's job is to absorb any fuel that may leak when doing step 2.
To see the location of the Schrader valve, go here: Location Of The Schrader Valve. - 2
Connect the fuel pressure gauge to the Schrader valve on your 3.0L Ford Ranger's fuel injector rail.
- 3
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 the connection at the Schrader valve for fuel leaks and if any tighten the fuel pressure a bit more (by hand only) to eliminate them. - 4
Your fuel pressure gauge should register the specified KOEO fuel pressure for the particular year of your 3.0L Ford in the table above if the fuel pump is OK.
Let's take a look at what your results mean:
CASE 1: The fuel pressure gauge registered 0 PSI. This confirms that the cause of your 3.0L Ford Ranger no-start problem is caused by a lack of fuel.
Now, I usually take 2 more precautions, before condemning the fuel pump as bad:
- Making sure the fuel pump inertia switch hasn't tripped (if it has tripped, then the fuel pump will not run). To see what the fuel pump inertia switch looks like, go to: Fuel Pump Inertia Switch.
- Making sure the fuel pump relay is feeding the fuel pump power (if the fuel pump relay is bad, then the fuel pump will not run).
CASE 2: The fuel pressure gauge registered the specified fuel pressure for your vehicle's model year. This test result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. The reason your 3.0L Ford Ranger is not starting is due to another reason. The fuel pump is OK.
