TEST 3: Jumpering The Fuel Pump Circuit

How To Test The Ford Fuel Pump Relay -No Start Troubleshooting (Green Relay)

OK, so far you have confirmed that the fuel pump relay on your Ford car or pickup is getting power on wires labeled with the numbers 2 and 4.

In this test step, we're gonna' jumper two wires (numbers 3 and 4) together to manually get the fuel pump to activate.

Although it's not absolutely necessary, you should connect a fuel pressure gauge to the Schrader Valve (on the fuel injector fuel rail), so that when you jumper the fuel pump to power, you can check that the fuel pressure the fuel pump is outputting is enough to start your vehicle.

If you're in need to a fuel pressure gauge, I recommend this one:

Actron CP7838 Professional Fuel Pressure Tester

This fuel pressure gauge is inexpensive (compared to how much you'll pay for one at your local auto parts store), and has the adaptor to test the fuel pressure on your Ford car and/or pickup.

OK, to get this test going, this is what you'll need to do:

  1. Connect your fuel pressure gauge to the Schrader Valve on the fuel rail.
  2. Disconnect the fuel pump relay from its connector.
  3. Locate the terminals labeled with the numbers 3 and 4.
  4. Using a jumper wire, jumper terminals 3 and 4 together.
    1. NOTE: Don't use anything that is too big to fit into the female terminals of the connector, OR you run the risk of damaging the metal terminals.
    2. By ‘damaging’, I mean that the female terminals will open up permanently and later cause a false contact that will become a headache later to troubleshoot.
  5. Turn the Key On (but don't crank the engine).
  6. You should hear the hum of the fuel pump (as it's activated) AND you should see the fuel pressure rise on your fuel pressure gauge.
    1. Fuel pressure should be between 35 to 45 PSI.

OK, let's interpret your test results:

CASE 1: Fuel pump came On and the fuel pressure was at specification (35 - 45 PSI). This tells you that the fuel pump is OK.

This test result indirectly tells you several things also:

  1. That the fuel pump Inertia Switch is OK (not tripped).
  2. That the wiring between the fuel pump and the fuel pump relay is OK.

The next step is to make sure that the EEC Computer (fuel injection computer) is activating the fuel pump. For this test, go to: TEST 4.

CASE 2: Fuel pump came On but the fuel pressure WAS NOT at specification (35-45 PSI). This tells you that the fuel pump is getting power but that it's bad and needs to be replaced.

To be a little more specific: you ca hear the fuel pump come on if you place your ear on the fuel tank filler tube, but the fuel pressure does not register any fuel pressure or the fuel pressure is way below the 35 PSI minimum.

CASE 3: Fuel Pump DID NOT come On and the fuel pressure WAS NOT at specification. This test result means one of two things:

  1. That the fuel pump is bad.
    1. To further check this, you'll need to confirm that the fuel pump Inertia Switch has not tripped by pushing down on its button and resetting it.
    2. Or, checking for 10 to12 Volts at the fuel pump connector itself (by the gas tank). NOTE: Checking that power (10 to 12 Volts) are actually reaching the fuel pump is a very important step before replacing it.
  2. The fuel pump Inertia Switch has been tripped and is not allowing current to reach the fuel pump.
    1. To check this, locate the fuel pump Inertia Switch and push down on its button. If the Inertia Switch has tripped, you'll hear (and feel) a clicking sound when pushing down on the reset button. It if hasn't tripped, then you won't hear (or feel) anything when pushing down on its reset button.

TEST 4: Checking That The Computer Is Activating The Fuel Pump Relay

How To Test The Ford Fuel Pump Relay -No Start Troubleshooting (Green Relay)

As you may already be aware, it's the fuel injection computer that activates the low current circuit of the fuel pump relay.

It does this by grounding the circuit internally (inside the computer itself) and this can be easily verified with a 12 Volt automotive test light (or a multimeter).

There are some very important precautions you have to take and keep in mind when testing this circuit and they are:

  1. Never apply 12 Volts to this circuit (either intentionally or accidentally), or you'll fry the computer.
  2. Never jumper circuit numbers 1 and 2 together, or you'll fry the computer.
  3. This test step has to be done with the engine cranking, so you have to be careful!

OK, to get this test going, this is what you'll need to do:

  1. Unplug the fuel pump relay from its connector.
  2. Connect your 12 Volt test light's alligator clip to the battery's positive (+) terminal.
  3. With the metal probe point of the test light, probe the wire identified with the number 1.
    1. What I recommend you do is to probe behind the fuel pump relay connector or probe the wire itself.
    2. Avoid probing the front of the fuel pump relay connector to avoid damaging the female terminal.
  4. Have a helper crank the engine for you as you observe the test light.
    1. IMPORTANT: Take all necessary safety precautions and think safety when working around a cranking engine.
  5. As long as the engine is cranking, the 12 Volt test light should come On and stay On.
  6. When done, turn the Key Off.
    1. With the Key Off (or out of the Ignition Switch), the 12 Volt test light should turn Off.

OK, let's interpret your test results:

CASE 1: The 12 Volt test light came On (and stayed On the whole time the engine was cranking). This is the normal and expected test result and it confirms that the fuel injection computer (EEC Electronic Control Module) is activating the fuel pump relay.

So far, if you started testing from the beginning, you have checked and confirmed that:

  1. The fuel pump relay's low current circuit (wire 2) is getting power (TEST 1).
  2. The fuel pump relay's high current circuit (wire 4) is getting power (TEST 2).
  3. That the fuel pump does come on and is producing the correct fuel pressure Specification (35 to 45 PSI) (TEST 3).
  4. In this test (TEST 4), you have confirmed that the computer is Grounding the relay's low current circuit.

The next step is to check that the fuel pump relay is sending power to the fuel pump. For this test, go to: TEST 5.

I also recommend taking a look at: TEST 6.

CASE 2: The 12 Volt test light DID NOT come On. Make sure that you're probing the correct wire and repeat the test one more time.

If your 12 Volt automotive test light still does not come On, then the PCM is not activating the fuel pump relay. I can tell you that it's extremely rare for the fuel injection computer to go bad and not activate the fuel pump relay (but I'm sure it happens).

The most likely problems causing this missing voltage are:

  1. An ‘open-circuit’ problem between the fuel injection computer (EEC Electronic Control Module) and the fuel pump relay connector.
  2. The PIP (Profile Ignition Pickup -which is the crankshaft position sensor inside the Distributor) is bad and not sending a PIP signal (Crank Position Signal) to the fuel injection computer.
    1. When this happens (a bad PIP Sensor), you'll also notice that there's NO SPARK at any spark plug wire.
    2. The ignition Coil won't be sparking either.

Ford Vehicles:

  • Aerostar
    • 1986, 1987, 1988, 1989, 1990, 1991, 1992
  • Bronco
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
  • Bronco II
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992

Ford Vehicles:

  • Country Squire
    • 1987, 1988, 1989, 1990, 1991
  • Crown Victoria
    • 1992
  • E100, E150, E250, E350
    • 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992

Ford Vehicles:

  • Escort
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • Explorer
    • 1991, 1992
  • F100, F150, F250, F350
    • 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992

Ford Vehicles:

  • Fairmont
    • 1981, 1982, 1983
  • LTD
    • 1981, 1982, 1983, 1984, 1985, 1986
  • LTD Crown Victoria
    • 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991

Ford Vehicles:

  • Mustang
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993
  • Ranger
    • 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992

Ford Vehicles:

  • Taurus
    • 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995
  • Tempo
    • 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994

Ford Vehicles:

  • Thunderbird
    • 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995

Lincoln Vehicles:

  • Continental
    • 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996

Lincoln Vehicles:

  • Mark VI
    • 1981, 1982, 1983
  • Mark VII
    • 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
  • Mark VIII
    • 1993

Lincoln Vehicles:

  • Town Car
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

Mercury Vehicles:

  • Cougar
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997

Mercury Vehicles:

  • Grand Marquis
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992
  • Lynx
    • 1981, 1982, 1983, 1984, 1985, 1986, 1987

Mercury Vehicles:

  • Marquis
    • 1980, 1981, 1982, 1983, 1984, 1985, 1986
  • Sable
    • 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995

Mercury Vehicles:

  • Topaz
    • 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994
  • Tracer
    • 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997