How To Test The Fuel Pump on Ford MPI (Ford 4.9L, 5.0L, 5.8L)

Testing to see if the fuel pump has failed (or not) on your Ford 4.9L, 5.0L, or 5.8L multi-port fuel-injected pickup/van isn't hard.

Ford was kind enough to install a Schrader valve on the fuel injector rail and it's to this valve that you and I can connect a fuel pressure test gauge to see if the fuel pump is working or not.

In this tutorial I'm gonna' explain the two methods used to check for a ‘no fuel’ condition causing a no-start condition.

One method involves using just starting fluid and the other involves using a fuel pressure gauge. One method is a very accurate way of diagnosing a lack of fuel condition causing a no-start. The other method is not that accurate.

IMPORTANT: Gasoline is extremely flammable. Be careful and take all necessary safety precautions. Use extreme care when using starting fluid since it ignites as easily as gasoline. Accomplishing both tests indicated in this article, without any unhappy consequences, is more than possible if you're careful and use common sense.

Symptoms Of A Bad Fuel Pump

A bad fuel pump will make your 4.9L, 5.0L, or 5.8L multi-port fuel-injected pickup (van or SUV) crank but not start. Here are some more specific symptoms:

  1. The ignition system is creating and delivering spark to the spark plugs. So you know that the ignition system is not at fault (in other words: the ignition control module is OK, the ignition coil is OK, etc.).
  2. You've sprayed starting fluid (or carburetor spray) into the throttle body and your vehicle started, even if only momentarily.
  3. You don't hear the fuel pump making a buzzing sound as you turn the key to the On position or crank the engine.
  4. You don't see the fuel injectors spraying gasoline.
  5. You've checked and confirmed that the fuel pump inertia switch HAS NOT activated.

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.

IMPORTANT: You should first check the fuel pump inertia switch before starting your fuel pump diagnostic. For more info go to: Checking The Fuel Pump Inertia Switch.

TEST 1: Using Starting Fluid

Using Starting Fluid. How To Test The Fuel Pump On Ford MPI (Ford 4.9L, 5.0L, 5.8L)

Spraying starting fluid (or carburetor cleaner spray) into the throttle body and having a helper crank the engine is usually the very first test that's done at an automotive repair shop to see if the no-start problem is due to a lack of fuel.

In a nutshell, if the fuel pump isn't supplying fuel, then the starting fluid will get the engine to start and run for a few seconds.

CAUTION: You'll be working around a cranking engine, so take all necessary safety precautions and think safety all of the time.

OK, to get this show on the road, this is what you'll need to do:

  1. 1

    Remove the intake air duct hose from the throttle body.. You don't have to completely remove them completely.

  2. 2

    Spray starting fluid down the bore of the throttle body. When you have sprayed a good squirt of starting fluid, quickly place the air intake duct hoses back on.

    IMPORTANT: Placing the intake air ducts back on the throttle body is important because it'll prevent any back-fire, that may occur, from spouting flames out of the throttle body.

  3. 3

    Have your helper crank the engine once the intake air ducts are back on the throttle body.

  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 means that the reason your pick up (or van) is not starting is due to a lack of fuel. This usually means that the fuel pump is bad.

To make sure the fuel pump has fried and stopped working, you now need to actually confirm how much pressure the fuel pump is producing with a fuel pressure gauge. For this test go to: TEST 2: Fuel Pressure Test With Gauge.

CASE 2: The engine did not start, not even momentarily. This usually means that a lack of fuel IS NOT the reason your pickup or van 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 test the fuel pressure with a fuel pressure test gauge.

Quite a few things can cause a ‘no-start’ condition and if you have ruled out the fuel pump as the problem, this tutorial may be of help: How To Troubleshoot A No Start (Ford 4.9L, 5.0L, 5.8L).