How To Troubleshoot A Bad Fuel Pump (Ford 4.6L, 5.4L)

You can easily verify if the no start condition on your Ford F150 (or Expedition, or Crown Victoria, or any 4.6L or 5.4L equipped car, pick up, or SUV) is due to a lack of fuel. In this ‘How To’ test article, I'm gonna' show you how to do it using one of two different diagnostic techniques.

One troubleshooting technique involves using starting fluid and the other involves using a fuel pressure gauge. Both methods will effectively let you know if the fuel pump is pumping fuel or not but only one is 100% accurate.

A word of caution: starting fluid and gasoline are extremely flammable, so you need to be very careful around them. The tests I'm presenting to you here can be easily and safely done (and I've done them lot's of times without any unwanted and unhappy accidents), if you take all necessary safety precautions, stay alert and use common sense.

En Español You can find this tutorial in Spanish here: Cómo Probar la Bomba de Combustible (Ford 4.6L, 5.4L) (at:

Symptoms Of A BAD Fuel Pump

When the fuel pump stops working, the most obvious symptom is that your 4.6L, 5.4L Ford (or Mercury or Lincoln) will ‘crank but not start’. Here are a couple of others that are more specific:

  1. You've got spark coming out of all of the Coil-on-Plug ignition coils or coil packs. So you know that the ignition system is not at fault.
  2. You've done a fuel injector Noid Light test, and all four fuel injectors are getting both 12 Volts and the activation signal.
  3. You've sprayed starting fluid into the throttle body and your vehicle started, even if only momentarily.

Although the above list is a not a very complete list of symptoms... the theme that runs thru' them, and any other related symptom, is that the engine will crank and crank, but not start.

NOTE: A fuel pump inertia switch that has triggered, will interrupt power going to the fuel pump. In layman's terms, this means the fuel pump will not run. So, it's always a good idea to check the fuel pump inertia switch first. For more info on this, see: Checking The Fuel Pump Inertia Switch.

FUEL PUMP TEST 1: Spraying Start Fluid Into The Throttle Body

Spraying Start Fluid Into the Throttle Body. How To Troubleshoot A Bad Fuel Pump (Ford 4.6L, 5.4L)

I'm going to jump into the lack of fuel troubleshooting with the starting fluid test. This is probably the fastest and the one that does not require any expense to do (like buying a fuel pressure gauge). With this test, you will be able to confirm if the no start condition, on your Ford Expedition (Cougar, Thunderbird, Explorer, Mountaineer, etc.), is being caused by a lack of fuel (although it's not the most accurate way of diagnosing a BAD fuel pump).

Before you jump into the actual test (on your F150, Mustang, Thunderbird, Navigator, Grand Marquis, etc.), you must first check that the ignition system is creating and delivering spark to all of the spark plugs. This is important cause if there's no spark... none of the tests in this article will help you. Not only that, this no spark results tells you that the cause of the no start is not due to a BAD fuel pump.

NOTE: If you haven't already, check the to make sure the fuel pump inertia switch isn't behind the no start problem. See: Checking The Fuel Pump Inertia Switch.

OK, enough talking... let's get this ball rolling:

  1. 1

    Disconnect the air intake duct from the throttle body. The end that connects to the air filter box (or canister) can remain connected to it.

  2. 2

    Manually open the throttle and spray starting fluid down the bore and then, quickly, reconnect the air duct to the throttle body (you don't have to tighten the Hose Clamp).

  3. 3

    Once the intake air duct is back on the throttle body, have your helper crank the engine.

    Having the intake air duct back on is a safety precaution, since the starting fluid could cause a back-fire to come out thru' the throttle body.

  4. 4

    One of two things is gonna happen:

    1.) The engine will start, even if it's just momentarily or for a few seconds and then die or.

    2.) The engine will only crank but not start at all.

Alright, let's interpret your results by choosing one of the following CASES:

CASE 1: If the engine started, even momentarily: This test result indicates that the no start condition your Ford vehicle is experiencing is due to a lack of fuel.

This test result usually confirms that the fuel pump is BAD (in about 80% of the cases) and replacing it will solve the no start problem but not always.

In about 20% of the cases, this lack of fuel could be caused by a blown fuse, a BAD fuel pump relay, a triggered fuel pump interrupt switch etc. So, keeping this in mind, I suggest you do two more things:

  1. 1

    Remove the fuel line that connects to the fuel injector rail (this is the one that delivers fuel from the fuel filter) and place it in a container. When ready, have your helper bump the starter motor while you verify if fuel comes out or not. No fuel coming out of the fuel line further confirms a BAD fuel pump.

  2. 2

    Find the wire (circuit) that feeds power (12 Volts) to the fuel pump and with a multimeter in Volts DC mode, verify that 12 Volts are reaching the fuel pump when you crank the engine.

CASE 2: The engine did not start, not even momentarily: This indicates that the no start condition is NOT due to a lack of fuel.

Now, since a starting fluid test is not the most accurate way to find out if the fuel pump is BAD, I suggest you do one more test...

... This is to use a fuel pressure gauge to see the exact amount of fuel pressure the fuel pump is producing. For more info on this test, go to: FUEL PUMP TEST 2: Using a Fuel Pressure Gauge.

Another handy tutorial is this one: How To Test A No Start Condition (Ford 4.6L, 5.4L).