How To Test The Fuel Pump (4.2L Ford E150, E250, F150)

How To Test The Fuel Pump (4.2L Ford E150, E250, F150)

Ford has made it easy to test the fuel pump on your 4.2L V6 equipped F150 (E150 and E250 van). This is due to the fact that Ford installed a Schrader valve on the fuel injector rail. It's to this Schrader valve that you and I can connect a fuel pressure gauge to and check fuel pressure.

Of course, testing a lack of fuel can be done in several ways. In this tutorial, I'll present to you the two most common: Using starting fluid and using a fuel pressure gauge.

In Spanish You can find this tutorial in Spanish here: Cómo Probar La Bomba De Gasolina (4.2L Ford E150, E250, F150) (at: autotecnico-online.com).

Symptoms Of A Bad Fuel Pump

Fuel pump failures fall into two categories: Total fuel pump failure and a slowly dying fuel pump.

Obviously, when the fuel pump completely fails, your 4.2L equipped pickup or van isn't gonna' start. In this type of scenario, you'll see that:

  1. The engine turns over but will not start.
  2. The ignition coil pack is creating and distributing spark to all 6 cylinders.
  3. The PCM will still pulse (activate) all 6 fuel injectors.

But when the fuel pump fails slowly, your Ford will start and run but with engine performance problems. You'll probably see one or more of the following symptoms:

  1. Rough idle.
  2. Engine starts after extended cranking.
  3. Lack of power when accelerating the vehicle down the road.
  4. 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 Ford with a Ford-type Schrader valve:

All of the fuel pump pressure test kits above have the fitting that will connect to your Ford's Schrader valve.

TEST 2: Checking Fuel Pressure With A Fuel Pressure Gauge

Checking Fuel Pressure With A Fuel Pressure Gauge. How To Test The Fuel Pump (4.2L Ford E150, E250, F150)

The most accurate way to find out if the fuel pump is bad is to use a fuel pressure gauge to test it (this is the way it's done in all professional repair shops).

As I mentioned before, we can connect a fuel pressure gauge to the fuel system using the Schrader valve located on the fuel injector rail.

Most fuel pressure gauge kits include an adapter to use. This adapter looks just like the one in the illustration above.

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.

  2. 2

    Connect the fuel pressure gauge to the Schrader valve on your 4.2L V6 Ford'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: 30 to 45 PSI with the Key On Engine Off (KOEO) 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 4.2L V6 engine's no-start problem is caused by a lack of fuel.

Now, I usually take one more precaution, before condemning the fuel pump as bad and this is to check that the fuel pump is getting 12 Volts as the engine is cranking. This is just to make sure that the fuel pump relay and fuse are OK and doing their job.

What you'll have to do to accomplish this is to attach a multimeter in Volts DC mode to the wire that supplies this voltage to the fuel pump and while a helper cranks the engine, verify that the fuel pump is getting this power. If the 12 Volts are being supplied to the fuel pump, you have now 100% verified that the fuel pump is fried and needs to be replaced.

CASE 2: The fuel pressure gauge registered 30 to 45 PSI. This fuel pressure gauge test result lets you know that the fuel pump is working and delivering enough fuel to the fuel injectors. The reason your 4.2L V6 F150 (E150 or E250) is not starting is due to another reason. The fuel pump is OK.

Ford Vehicles:

  • E150 4.2L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003
  • E250 4.2L
    • 1997, 1999, 2000, 2001, 2002, 2003
  • F150 4.2L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006