How To Test The Fuel Pump (1992-2000 3.0L Ford Ranger)

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.

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:

1. The engine turns over but will not start.
2. The ignition coil pack feeding spark to all 6 cylinders.
3. The PCM will still pulse (activate) all 6 fuel injectors.
4. Fuel pressure PSI is 0 PSI at the Schrader valve test port.
5. 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:

1. Lean air/fuel mixture trouble codes.
2. Rough idle.
3. Engine starts after extended cranking.
4. Lack of power when accelerating the vehicle down the road.
5. 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:

NOTE: 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. 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. 2

   Connect the fuel pressure gauge to the Schrader valve on your 3.0L Ford Ranger's fuel injector rail.

3. 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. 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.

TEST 2: Using Starting Fluid To Confirm Lack Of Fuel

Although using starting fluid to check a no-start is not the most accurate way to test the fuel pump, it's the fastest way to jump start your troubleshooting efforts.

I've been using the starting fluid test, to diagnose a lack of fuel causing a no-start problem, ever since I've been working on cars professionally but let me tell you that the successful outcome of this test depends on making sure that all 6 cylinders are getting spark.

This means that, to get an accurate test result, you have to first check all (or at least the majority of) cylinders for spark test with a dedicated spark tester before you perform the starting fluid test.

IMPORTANT: This is a very fast and easy test but you do have to take one very important safety precaution and this is to reconnect the air intake duct after spraying starting fluid down the throttle bore (although you don't have to fasten it). This will prevent any backfire, that might occur, from scaring the heck out of you when cranking the engine.

This is what you have to do:

1. 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. 2

   Open the throttle plate and spray starting fluid down the bore.
   
   As a safety precaution reconnect the air duct after you have sprayed a good squirt of starting fluid (but you don't have to tighten the air duct's hose clamp).

3. 3

   Crank the engine once the air duct is back on and you're clear of the engine compartment.

4. 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 find out what your results mean:

CASE 1: The engine started and ran for a few seconds. This test result tells you that the no-start problem is due to a lack of fuel.

Your next step is to check to see what the fuel pressure is with a fuel pressure test gauge. Go to: TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.

CASE 2: The engine did not start, not even momentarily. This usually means that 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 check the fuel pressure with a fuel pressure test gauge. Go to: TEST 1: Checking Fuel Pressure With A Fuel Pressure Gauge.

Location Of The Schrader Valve

NOTE: The photo above is of a 1999 3.0L Ford Ranger's Schrader valve.

The Schrader valve is located on the fuel injector rail (on the majority of vehicles covered by this tutorial). This is the fuel rail that feeds injectors for cylinders 1, 2, and 3. As you can see in the photo above, it's next to the ignition coil pack.

Fuel Pump Inertia Switch

Your Ford comes equipped with a fuel pump inertia switch, whose job is to de-activate the fuel pump in case of an impact and thus prevent a possible fire from fuel spilling. It's usually located on the right side (passenger side) of the dash, below the glove box.

When the inertia switch is jolted into action, the engine is not gonna' start. It'll crank but not start, which can lead you to believe that the fuel pump is bad.

Although it's designed to activate during a severe impact caused by an automobile accident, sometimes it gets activated by less than severe impacts. This means that it's always a good idea to check and reset the inertia switch whenever testing the fuel pump.

Resetting the fuel pump inertia switch simply involves pushing down on the button located on top of the inertia switch till it bottoms out.

Where To Buy The Fuel Pump And Save

The fuel pump in your 3.0L Ford Ranger is located inside the fuel tank. The fuel pump can be bought in any auto parts store, but I think you'll find the better price online. The following fuel pumps are pretty good deals:

1990-1996

1998-2000

Not sure if the above fuel pumps fit your particular 3.0L Ford Ranger? Don't worry, once you get to the site, they'll make sure it fits by asking you the specifics of your vehicle. If it doesn't fit, they'll find you the right one.