Replacing The Fuel Pump Diode In A 2002 Lincoln Ls

If your 2002 Lincoln LS is not starting, it could be due to a faulty fuel pump diode. The fuel pump diode is located in the trunk power distribution box (PDB). To replace it, you will need to remove the rear seat and access the PDB. Once you have located the fuel pump diode, you can replace it with a new one. It is recommended to replace the fuel filter as well when changing the fuel pump diode.

Location of the fuel pump diode

The fuel pump diode in a 2002 Lincoln LS is located in the trunk power distribution box (PDB). To access the fuel pump, you will need to get to the fuel pump access door, which is usually located underneath the rear seat. In some vehicles, you may need to drop the fuel tank to access the pump.

The main fuel pump is located behind the passenger rear seat bottom. There is also a jet pump to stabilize the fuel in the saddle gas tank, which is behind the driver's rear seat bottom under a 6" rubber cover.

How to check if the fuel pump diode is faulty

To check if the fuel pump diode in your 2002 Lincoln LS is faulty, you can perform the following tests:

Listen for the Fuel Pump

Place your ear near the fuel tank and turn the ignition key to the "on" position. A correctly functioning fuel pump should make an audible noise. If you don't hear anything, the fuel pump or diode could be faulty.

Whack the Fuel Tank

This test involves hitting the fuel tank with a rubber mallet while an assistant cranks the engine. If the car starts during this procedure, it indicates that the electric motor inside the pump is faulty. Whacking the tank temporarily jars the motor, and while this test may get the motor running, it is only a temporary fix and the fuel pump will need to be replaced.

Use Starter Fluid (With Caution)

This test carries a risk of personal injury and potential engine damage, so it should only be performed with the proper safety equipment, such as safety glasses and a fire extinguisher. Do not use starter fluid on a diesel engine. During the test, spray starter fluid into the throttle body while an assistant cranks the engine. If the engine starts and runs momentarily, it indicates a fuel-related problem, which may be due to a bad pump.

Check for Diagnostic Trouble Codes (DTCs)

Diagnostic trouble codes can be checked using a scanner or code reader. These codes are set in the car's computer and may be directly related to the fuel pump or refer to an air/fuel ratio problem. Many auto parts stores will pull these codes for free, and there are also inexpensive code-reading tools and smartphone apps available.

Check Fuel Trim with a Scan Tool

This test applies if the engine is running. Scan tools will display a data parameter called short-term fuel trim (STFT). Generally, fuel trim readings should be between -10 and 10. If the fuel trim is above 10, the engine is running lean, and the fuel pump may not be delivering enough fuel. However, other factors such as vacuum leaks can also cause lean conditions, so checking fuel pressure is the next recommended step.

Check Fuel Pressure and/or Volume

Checking fuel pressure and/or volume will indicate whether enough fuel is making it from the tank to the engine. This can be done using a mechanical fuel pressure gauge, which is inexpensive and readily available. Most modern vehicles have a test port located on the fuel rail, making it easy to perform a static fuel pressure test.

Connect the gauge as outlined in your repair manual, turn the ignition to the "on" position (engine off), and note the reading. Compare this reading to the specification listed in your repair manual. If the reading is significantly different from the specification, it may indicate a faulty fuel pump.

Additionally, you can perform a static fuel pressure test to see if the pressure holds. Consult your repair manual to determine how long the fuel pressure should hold once the pump is turned off. If the pressure bleeds off too quickly, there is a fuel-related problem, such as a bad pump check valve or faulty regulator.

Advanced Tests

There are also some advanced tests that can be performed using specialized equipment, such as an oscilloscope or a professional-grade scan tool. These tests can provide more detailed information about the fuel pump's condition.

How to remove the fuel pump diode

To remove the fuel pump diode on a 2002 Lincoln LS, you will first need to locate the diode. The fuel pump diode is located in the trunk power distribution box (PDB) behind the battery.

• Open the trunk of your Lincoln LS.
• Locate the battery. It is typically placed on one side of the trunk, either the left or right, depending on your model.
• Remove the cover of the power distribution box, which is located behind the battery. You may need to remove the battery or move it to the side to access the PDB cover easily.
• Once you have accessed the PDB, locate the fuel pump diode. It should be labelled as such, or you can refer to your Lincoln LS service manual for a diagram and specific location.
• Before proceeding, ensure that the ignition is turned off, and disconnect the negative terminal of your car battery to prevent any accidental electrical shorts.
• Identify the wires connected to the fuel pump diode. There should be at least two wires, one for power and one for ground.
• Using appropriate tools, carefully detach the wires from the diode. You may need to use a small screwdriver to release the wire connectors.
• Now, you can remove the fuel pump diode from its housing. It may be secured in place with screws or clips, so use the necessary tools to carefully remove it without damaging any surrounding components.
• With the diode removed, inspect it for any signs of damage, corrosion, or wear. A faulty diode may exhibit physical signs of malfunction, such as burnt marks or melted plastic.
• If you are replacing the diode, make sure to install the new one securely and connect the wires correctly, following the colour-coding or labels.

Remember to reattach any components you had to remove or move during the process, and always exercise caution when working with electrical systems in your vehicle.

How to install a new fuel pump diode

To install a new fuel pump diode in a 2002 Lincoln LS, you will first need to locate the diode in the trunk power distribution box (PDB). The PDB is located behind the battery in the trunk.

Once you have located the PDB, you will need to remove the old diode. To do this, simply unplug the diode from the PDB. Be careful not to damage any of the other components in the PDB.

Next, take your new diode and plug it into the PDB. Make sure that it is securely connected.

Finally, you will need to test your new diode to ensure that it is functioning properly. Turn the key to the "on" position and check for power at the green/orange wire and pulsed ground at the black/red wire. If you have power, your new diode is installed correctly and should be functioning properly.

If you do not have power, you may need to check the fuses. There are two fuses that you should check: F204 (5 amp) in the passenger kick panel and F417 (15 amp) in the trunk PDB. Check for battery power on both sides of the fuse with the key on. If the fuses are blown, replace them and retest the diode.

What to do if the fuel pump still doesn't work

If the fuel pump in your 2002 Lincoln LS still doesn't work, there are a few things you can check and some potential issues you can investigate.

Firstly, check if you can hear the fuel pump when you turn the key. If you don't hear it, the pump may be faulty or not receiving power.

If the pump is not the issue, there are a few other potential causes. One possibility is the fuel pump shut-off switch, which may need to be reset. This switch is located behind the left kick panel. Another cause could be blown fuses. There are two fuses you should check: one in the kick panel on the passenger side floor and the other in the trunk in the power distribution box.

Additionally, a bad fuel pump relay could be the culprit. This relay is also located in the trunk's power distribution box. Finally, a faulty fuel pump diode, which is in the same location as the relay, could be the issue.

If none of these solutions work, it may be best to consult a professional mechanic or seek further advice specific to your situation.

Frequently asked questions