Replacing The Fuel Pump Relay In A 1999 Ford Ranger

If you're experiencing issues with your 1999 Ford Ranger's fuel pump, you may need to replace the fuel pump relay. The fuel pump relay failure could be due to several reasons, including current overload, short circuit, or defective internal components. Before replacing the relay, it's important to confirm that it is indeed the issue by testing it with a multimeter or replacing it with another relay of the same specifications. If the relay is functioning correctly, other potential causes of fuel pump failure include a blown fuse, impact sensor activation, engine control unit (ECU) issues, or a clogged fuel filter. Troubleshooting and repairing a fuel pump issue can be complex, so it's recommended to seek assistance from a qualified mechanic or refer to a reliable repair manual specific to your vehicle.

How to test a fuel pump relay

To test a fuel pump relay, you will need a multimeter or a voltmeter, and some jumper/test leads.

First, locate the fuel pump relay in the fuse box. The fuse box is usually located underneath the hood near the front of your vehicle, but there may also be a smaller fuse box under the steering column inside your car. The fuel pump relay is usually coloured green or grey.

Next, turn off your vehicle and remove the key from the ignition. Then, pull the relay straight out from the fuse box. You can try to put a new relay in the fuse box and start your vehicle. If it starts without a problem, then the old relay is broken.

If you want to test the old relay, you can use a multimeter or voltmeter to check the resistance going through the relay's circuit.

Using a multimeter:

• Set your multimeter to the ohm setting (Ω).
• Attach jumper wires to the terminals on your vehicle's battery.
• Connect the jumper wires to the positive and negative relay terminals.
• Listen for a clicking sound when you attach the power.
• Hold the multimeter probes against the other two prongs on the relay.
• Check the multimeter for a 0 reading to know the relay still functions.

Using a voltmeter:

• Set the volt meter to Ohms (measures resistance).
• Connect to terminals 30 and 87.
• Connect the other two leads to 12V+ and 12V- on your battery.
• You should hear a click, and the resistance should drop to 0 on the voltmeter.

If the relay is functioning correctly, the problem may lie elsewhere, such as a blown fuse, impact sensor activation, engine control unit (ECU) issues, a clogged fuel filter, fuel pressure problems, wiring problems, or a defective fuel pump.

Common issues with the fuel pump relay

One of the most common issues with the fuel pump relay in a 1999 Ford Ranger is the inertia switch only receiving 6 volts. This can cause the fuel pump to not receive enough power to operate, resulting in the vehicle not starting.

Another common issue is a blown fuse. The fuse protecting the fuel pump relay or the fuel pump fuse itself may blow due to an electrical problem, such as a damaged wire coming into contact with the vehicle's body. This can prevent the pump from receiving power and cause it to malfunction.

Additionally, the fuel pump relay may fail due to current overload or a short circuit in the electrical system. This can cause the relay contacts to overheat and burn out, or damage the relay's coil.

Defective internal components in the relay, such as the electromagnetic coil or mechanical contacts, can also fail over time due to repeated use, vibrations, or age.

It is important to note that there are other potential causes of fuel pump failure in the 1999 Ford Ranger, such as impact sensor activation, engine control unit (ECU) issues, clogged fuel filter, fuel pressure problems, wiring problems, or a defective fuel pump itself.

How to reset the ECU

Resetting the ECU (Engine Control Unit) of a 1999 Ford Ranger involves clearing the trouble codes in the PCM (Power Control Module). Here is a step-by-step guide on how to do this:

First, put the vehicle in park and turn off the ignition. Then, open the hood and locate the car battery. Place an adjustable wrench on the bolt securing the negative battery cable to the negative terminal. Adjust the wrench until it fits snugly, then loosen the bolt until you can remove the cable.

Wait for at least 15 minutes, and up to 20 minutes or an hour, depending on the source. Then, reattach the negative battery cable to the terminal and tighten it with the wrench. Start the vehicle to confirm the check engine light is no longer on.

Note that you will need to reprogram your radio station presets and reset the time, as these will be erased when the battery is disconnected. Some sources also suggest driving at various RPMs and speeds to "relearn" the PCM.

This process can also be done with an OBDII scanner, although this may require more expensive diagnostic equipment.

How to check for a blown fuse

A blown fuse is a common issue with a 1999 Ford Ranger, and it can cause a range of electrical problems. To check for a blown fuse, follow these steps:

Step 1: Locate the fuse box

Your 1999 Ford Ranger may have up to four fuse boxes located in different parts of the vehicle. The most common locations for fuse boxes are beneath the dashboard and underneath the back seats. Refer to your user manual to determine which fuse box controls the circuit you suspect is affected.

Step 2: Identify the individual fuse

Once you've located the fuse box, you need to identify the suspect fuse. Most fuse boxes have a diagram explaining the function and location of each fuse. If your fuse box doesn't have a diagram, you can use a test light or a multimeter to test the fuses.

If using a test light, attach the clip to any exposed metal, then use the probe to touch each end of each fuse. If the fuse is working properly, the test light will illuminate on both sides. If the fuse has blown, only one side of the test light will light up.

Alternatively, you can use a multimeter to test for continuity across fuses. Set the multimeter to 20K ohms, then touch both sides of the fuse with the device's probes. A good fuse will read 0.00. If you see a different number, the fuse is blown.

Step 3: Remove and inspect the fuse

After turning off the car, remove the suspect fuse using a fuse puller or needle-nose pliers. Grip the fuse with the tool, and hold it up to the light. Look through the translucent body of the fuse for the thin metal wire inside. If the wire appears broken or in two pieces, the fuse has blown and needs to be replaced.

Step 4: Replace the blown fuse

Replace the blown fuse with an identical one of the same type and amperage rating to prevent further issues. Push the new fuse into the correct slot in the fuse box, then start your vehicle to see if the issue has been resolved. If the problem persists, contact your local mechanic for a professional diagnosis.

How to check for wiring problems

Wiring problems can be a cause of fuel pump failure in the 1999 Ford Ranger. To check for wiring problems, you can perform the following steps:

• Check for damaged, corroded, or loose wires. Look for any signs of damage, such as fraying, melting, or exposed wires. Corrosion may appear as a white, green, or blue powder on the wire connectors.
• Test for power at the fuel pump. Use a multimeter to check for voltage at the fuel pump connector. With the key in the "on" position, you should have 12 volts at the fuel pump. If there is no power, check the fuses and relays associated with the fuel pump.
• Check the inertia switch. The inertia switch is a safety feature that cuts off power to the fuel pump in the event of an accident. Ensure that the red button on the switch is depressed. If the switch is activated, you may need to reset it or replace it.
• Verify fuel pump operation. If you have access to the fuel pump, you can connect it directly to a 12-volt power source to test its operation. If the fuel pump runs when connected directly to power, the issue is likely related to wiring or relays.
• Check for voltage at the fuel pump relay. With the key in the "on" position, use a multimeter to check for voltage at the fuel pump relay. The relay should have power on one of the large terminals. If there is no power, check the fuses and wiring associated with the relay.
• Test the fuel pump relay. You can test the relay by jumping the two large terminals with a small screwdriver or paper clip. This will bypass the relay and send power directly to the fuel pump. If the fuel pump runs with the relay jumped, the relay may be faulty and need replacement.
• Inspect the wiring harness. Ensure that the wiring harness connected to the fuel pump and inertia switch is intact and not damaged. Corrosion or damage to the wiring harness can cause a loss of power to the fuel pump.
• Refer to a wiring diagram. Obtain a wiring diagram specific to your 1999 Ford Ranger and carefully inspect each wire and connection. This will help you identify any potential issues or discrepancies in the wiring.

It is important to note that working with automotive electrical systems can be complex and hazardous. Always exercise caution and refer to a qualified mechanic or technician if you are unsure about any procedures.

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