How To Test The Fuel Pump (1990-1997 2.3L Ford)

As you're probably already aware, the engine in your 2.3L Ford Ranger (Mustang, Mazda B2300) needs 3 things to start. These are fuel, air and spark.

The major component that provides the fuel the engine needs to start is the in-tank electric fuel pump.

Testing it isn't difficult and in this tutorial I'll give you some pointers on how to do it and more importantly, the fuel pressure specifications of the fuel pump.

You can find this tutorial in Spanish here: Cómo Probar La Bomba de Gasolina (1990-1997 2.3L Ford) (at: autotecnico-online.com).

Symptoms Of A Bad Fuel Pump

When the fuel pump, in your 2.3L Ford Ranger (Mustang, Mazda B2300) fails, you'll see the following symptoms:

1. The engine will crank but not start.
2. Ignition system will still create and deliver spark to all 4 cylinders.
3. The PCM will still pulse (activate) all 4 fuel injectors.
4. The fuel pump inertia switch has not activated (in other words, it's not cutting power to the fuel pump).
   • To find out more about the inertia switch, go here: Checking The Fuel Pump Inertia Switch.

The Two Methods To Troubleshoot The Fuel Pump

There are two very basic ways to find out if the no-start your 2.3L Ford Ranger (Mustang, Mazda B2300) is being caused by a lack of fuel (a bad fuel pump).

One way involves using starting fluid and the other involves using a fuel pressure test gauge.

Both test tests are effective but the most accurate of the two is the checking for a lack of fuel with a fuel pressure test gauge.

Using Starting Fluid: The idea behind using starting fluid is to use the fluid as a substitute for gasoline.

The starting fluid is sprayed into the throttle body and then the engine is cranked. If the no-start is being caused by a lack of fuel, the engine will start. Now, it won't stay running, because as soon as the starting fluid that was sprayed in the throttle body is consumed, the engine will stall and cut off.

Although the engine doesn't stay running, this test result is enough to tells you that your 2.3L Ford Ranger's no-start problem is due to a lack of fuel (probably from the fuel pump).

Using A Fuel Pressure Gauge: This is the more accurate of both tests.

Ford was kind enough to install a Schrader valve on the fuel injector rail where you and I can install a fuel pressure gauge and measure the exact fuel pressure the fuel pump is outputting while the vehicle is being cranked.

IMPORTANT: Gasoline and starting fluid are extremely flammable. Take all necessary safety precautions while working around fuel. Safety is your responsibility. Be careful, stay alert, and use common sense.

TEST 1: Using Starting Fluid To Confirm A Lack Of Fuel

As mentioned earlier, the idea behind using starting fluid is to confirm that a lack of fuel is causing your 2.3L Ford Ranger (Mustang or Mazda B2300) to crank but not start.

This is usually the very first thing that most techs will do when they suspect that the fuel pump is bad (or that the no-start problem is due to a lack of fuel).

NOTE: To get an accurate test result from the starting fluid test, you need to first check and confirm that the ignition system on your 2.3L Ford Ranger (Mustang or B2300) is creating and feeding spark to all 4 cylinders. Without spark already present... the starting fluid test won't prove or disprove that a lack of fuel is the problem behind the no-start condition.

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: If the engine started and ran for a few seconds. This test result tells you that the reason your 2.3L Ford Ranger (Mustang, Mazda B2300) is cranking but NOT starting is due to a lack of fuel.

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.