TEST 1: Checking For Power (Low Current Circuit)

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

The very first thing that you and I need to do, is to make sure that the fuel pump relay is getting power.

This power is in the form of battery voltage and will range between 10 to 12 Volts DC.

Power is supplied to two circuits (wires). These two wires are the ones labeled with the number 2 and the number 4.

In this test, we'll focus on testing wire number 2 first (this wire is the one that feeds power to the low current circuit).

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

  1. Expose the fuel pump relays' 4 wires
    1. These 4 wires are usually wrapped in black electrical tape.
  2. Locate the wire that corresponds to circuit number 2.
  3. Set your multimeter in Volts DC mode and:
    1. With an appropriate tool (like a Wire Piercing Probe), pierce the wire labeled with the number 2 (in the image viewer) with the red multimeter test lead.
    2. NOTE: It's not possible to probe the front of the connector or you run the risk of damaging the metal female connector inside.
  4. Ground the black multimeter test lead directly on the battery negative terminal or on a clean metal spot on the engine.
  5. Turn the Key On.
  6. Your multimeter should register one of two things:
    1. Battery voltage (10 to 12 Volts DC).
    2. Or no voltage at all.
  7. When done, turn the Key Off.

OK, let's interpret your test results:

CASE 1: Your multimeter showed battery power. This tells you that the low current circuit of the fuel pump relay is getting juice and this is a good thing.

The next step is to verify that the fuel pump relay's high current circuit is being fed with battery power too. Go to: TEST 2.

CASE 2: Your Multimeter DID NOT show battery power. Recheck all of your multimeter connections and repeat the test one more time.

If the multimeter still does not register battery voltage (10 to 12 Volts DC) this second or third time around, then you need to find out why this voltage is missing (this voltage is provided by the EEC Power Relay).

Without voltage in this wire (with the Key On or Engine Cranking), the fuel pump relay will not activate the fuel pump.

TEST 2: Checking For Power (High Current Circuit)

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

So far, you have checked and confirmed that the low current circuit of the fuel pump relay is getting power (TEST 1).

The next step, in troubleshooting the fuel pump relay, is to make sure that it's getting battery power on wire labeled with the number 4.

This wire is the one that supplies power to the Ford fuel pump relay's high current circuit.

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

  1. Place your multimeter in Volts DC mode.
  2. With the Red Multimeter Lead, probe the wire labeled with the number 4.
    1. This is where a Wire Piercing Probe comes in handy (to see what this tool looks like, click here: Wire Piercing Probe).
    2. NOTE: It's not a good idea to probe the front of the fuel pump relay connector, since the metal female terminal could get damaged.
  3. Ground the black multimeter test lead directly on the battery negative terminal or on a clean metal spot on the engine.
  4. Turn the Key On.
  5. Your multimeter should register one of two things:
    1. Battery voltage (10 to 12 Volts DC).
    2. Or no voltage at all.
  6. When done, turn the Key Off.

OK, let's interpret your test results:

CASE 1: Your multimeter showed battery power. This is the normal and expected test result and it confirms that the high current circuit (that feeds the fuel pump itself with power) is being fed power.

The next step is to jumper wires number 3 and number 4 of the fuel pump relay connector to manually get the fuel pump to come On. Go to: TEST 3.

CASE 2: Your Multimeter DID NOT show battery power. Recheck all of your multimeter connections and repeat the test one more time.

If the multimeter still does not register battery voltage (10 to 12 Volts DC) this second or third time around, then you need to find out why this voltage is missing.

These 10 to 12 Volts are provided by the ignition switch (with the Key On or Engine Cranking), and if they are missing, the fuel pump relay will not activate the fuel pump.

Ford Vehicles:

  • Aerostar
    • 1986, 1987, 1988, 1989, 1990, 1991, 1992
  • Bronco
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Ford Vehicles:

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Ford Vehicles:

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Ford Vehicles:

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Lincoln Vehicles:

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Lincoln Vehicles:

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Lincoln Vehicles:

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Mercury Vehicles:

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Mercury Vehicles:

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