Replacing The Fuel Pump Relay In Your Buick 350 Engine

The fuel pump relay is a device that sends an electric current to the fuel pump, which then sends gasoline to the engine, allowing the car to start running. The fuel pump relay is also called the relay switch and its functions are similar to those of the automotive fuse. The fuel pump relay is controlled by the engine control module and is usually found under the hood or under the dashboard, near the steering wheel. Fuel pump relays can oxidize or rust and need to be changed frequently. Now, to change the fuel pump relay in a Buick 350, you would typically follow these steps:

1. Raise and support the vehicle hood.

2. Remove the defective fuel pump relay.

3. Install the new fuel pump relay.

4. Test the fuel pressure and clear codes with a scanner or gauge.

5. Close the vehicle hood and road test for proper operation.

Locating the fuel pump relay

The fuel pump relay is typically located under the hood or under the dashboard, near the steering wheel of the car. In some Buick models, such as the 1987 Chevy Truck, the fuel pump relay is located on the right-hand side of the engine compartment. For a 1997 Buick LeSabre, the fuel pump relay is located to the right of the glove box.

It is important to note that not all Buick models have a fuel pump relay. For example, the 2010 Buick Enclave does not have a fuel pump relay as it uses Direct Injection for its fuel injection setup. Instead, it uses a Fuel Pump Flow Control Module, which is located under the car, towards the rear of the fuel tank.

Once you have located the fuel pump relay, you can proceed with the next steps of changing the fuel pump relay in your Buick 350.

Removing the defective relay

To remove the defective relay, you will first need to locate the fuel pump relay. Depending on the make of your car, it may be found under the hood or under the dashboard, near the steering wheel. Once you have located the fuel pump relay, follow these steps:

• Raise and support the vehicle hood.
• Identify the defective fuel pump relay. It is a black plastic component, set in a small box with a wiring harness attached to its underside.
• Disconnect the wiring harness from the fuel pump relay.
• Remove the fuel pump relay from its mounting location. This may involve unscrewing or unclipping any mounting brackets or fasteners.
• Visually inspect the fuel pump relay for any signs of damage, such as oxidation or rust.
• Compare the defective fuel pump relay with a new one to ensure you have purchased the correct replacement part.

It is important to note that you should only attempt this repair if you have sufficient knowledge and experience in automotive repairs. If you are unsure, it is recommended to consult a certified mechanic to avoid any potential damage to your vehicle.

Installing a new fuel pump relay

Step 1: Raise and Support the Vehicle Hood

Before beginning any work on your Buick, it is important to ensure the vehicle is securely raised and the hood is supported to provide ample space to access the engine.

Step 2: Locate and Remove the Defective Fuel Pump Relay

The fuel pump relay is a small black plastic component, often found in a small box with a wiring harness attached to its underside. Depending on the make of your car, it may be located under the hood or under the dashboard near the steering wheel. Once located, carefully remove the defective fuel pump relay.

Step 3: Install the New Fuel Pump Relay

With the defective relay removed, you can now install the new fuel pump relay. Ensure it is securely fitted and the wiring harness is connected properly.

Step 4: Test the Fuel Pressure and Clear Codes

After installing the new fuel pump relay, test the fuel pressure using a scanner or gauge. This step is crucial to ensure the new relay is functioning correctly and that the fuel pump is receiving the correct amount of current.

Step 5: Close the Vehicle Hood and Road Test

Once you have confirmed the fuel pressure is within the normal range and all codes have been cleared, close the vehicle hood and take your Buick for a road test to ensure it is running properly.

Additional Information:

The fuel pump relay is an important component that sends an electric current to the fuel pump when you turn on the ignition. While the fuel pump operates as long as the engine is running, the fuel pump relay only works during startup and when you turn off the ignition. Due to its function, the fuel pump relay is prone to damage, especially the coil and contact points, and may need to be replaced more frequently than the fuel pump itself.

Symptoms of a malfunctioning fuel pump relay include an engine that cranks but does not start, irregular engine function, the car slowing down without braking, and the car coming to a halt after running a short distance.

It is important to keep the fuel pump relay in perfect working order. If it malfunctions, it can conduct too much power to the fuel pump, leading to damage or complete failure.

Testing the fuel pressure

Step 1: Prepare for Testing

Before beginning, exercise extreme caution as the fuel system is under pressure, and any mishandling can lead to fire or damage to painted surfaces. It is recommended to go through all the steps before starting the testing procedure. Ensure you have the necessary tools, such as a fuel pressure tester, a jumper wire, and safety equipment like gloves and eye protection.

Step 2: Access the Fuel Rail

Remove the plastic cover from the intake manifold to expose the fuel rail. This will allow you to access the Schrader valve, which is located on the fuel rail.

Step 3: Attach the Fuel Pressure Tester

Unscrew the cap from the Schrader valve. Be cautious, as the cap might be tight, and you may need pliers to loosen it. However, be gentle to avoid damaging the valve. Once the cap is removed, quickly screw the fuel pressure tester onto the valve to minimize fuel loss. Check for any fuel leaks, and clean up any excess fuel before proceeding.

Step 4: Test Pump Pressure

Instruct your assistant to turn the ignition switch to the "Run" position without starting the engine. Observe the reading on the fuel pressure tester. The fuel pump will run for about 2 seconds each time the ignition key is turned to the "Run" position. Be vigilant for any fuel leaks, and if observed, address the leak and clean up the spilled fuel before repeating the test. Repeat this step to verify consistent results.

Step 5: Interpret the Test Results

A normal reading for this test is between 40-47 psi. If your Buick 350 is within this range and you are still experiencing starting issues, the problem lies elsewhere, and fuel pressure is not the culprit. If the pressure is above 35-39 psi, it is slightly out of the normal range, but the engine should still function. However, if the pressure is significantly lower than 35 psi, you may encounter starting difficulties and poor engine performance. In such cases, you should perform the fuel pump load test described below.

Step 6: Fuel Pump Load Test

This test bypasses the fuses and relays to comprehensively test the fuel pump's performance under continuous operation. Ensure the ignition key is in the "Off" position. Use a 14-gauge or larger wire to connect the green fuel pump prime/test connector to the positive side of the battery. This will supply the fuel pump with 12 volts, and it should start running. Observe the fuel pressure tester for 15 to 30 seconds. The pressure should reach and maintain a steady reading between 40 and 47 psi, with fluctuations of no more than 1-2 psi. If you notice significant fluctuations, it indicates a problem, which could be due to a defective fuel pressure regulator or a restriction, such as a blocked fuel filter or a dirty sock/filter at the bottom of the pump. If the pump fails to run, there may be a bad connection or a defective fuel pump.

Step 7: Fuel System Pressure Hold Test

For this test, ensure the ignition key is in the "Off" position. Use a 14-gauge or larger wire to connect the green fuel pump prime/test connector to the positive side of the battery, which should start the pump. Allow the pump to run and build maximum pressure for about 10 seconds. Then, disconnect the wire powering the pump from the battery and continue observing the fuel pressure tester for about 15 seconds. Ideally, the pressure should remain steady without dropping. If you notice a rapid pressure drop, it indicates an issue with the fuel system, which could be due to a leaking fuel injector, a faulty check valve in the fuel pump, or a faulty fuel pressure regulator.

Clearing codes with a scanner or gauge

After the fuel pump relay has been replaced, the fuel pressure is tested, and the codes are cleared using a scanner or gauge. This is a crucial step in the process of changing the fuel pump relay in a Buick 350. Here is a detailed, step-by-step guide on how to clear the codes using a scanner or gauge:

Clearing Codes with a Scanner:

• Locate the OBD-II Port: The OBD-II port is usually found near the steering column, under the dashboard. This port allows access to the vehicle's diagnostic information.
• Turn on the Ignition: Turn the ignition key to the "ON" position without starting the engine. If your Buick has a START/STOP feature, press the button without pressing the brake pedal.
• Connect the Scanner: Plug the scanner into the OBD-II port. Ensure that the vehicle is turned off before connecting the scanner.
• Access the Diagnostic Menu: On the scanner's display, navigate to the "Diagnostic" or "Scan" menu. This menu will allow you to perform various diagnostic functions.
• Select the Vehicle Make: Choose "Buick" as the vehicle make to ensure effective communication with the Buick's on-board diagnostic system.
• Select the Vehicle Model: Scroll through the available options and select the correct model and chassis/body type for your Buick. This step is crucial for proper synchronization between the scanner and your vehicle.
• Select Control Modules: You can choose to perform a "Quick Scan" or select specific control modules, such as the Engine Control Module (ECM) or Transmission Control Module (TCM), for diagnosis.
• Retrieve and Interpret the Codes: The scanner will display the fault codes along with their descriptions. Note these codes down for further analysis and diagnosis.
• Erase the Codes: After the issue has been resolved, return to the scanner's menu and select the option to "Erase Codes" or "Clear Codes." This will remove the stored fault codes, indicating that the problem has been addressed.

Clearing Codes with a Gauge:

While the previous steps outline the process of clearing codes with a scanner, it is important to note that some gauges may have different buttons or functions. Here are the general steps for clearing codes with a gauge:

• Connect the Gauge: Ensure the vehicle is turned off. Locate the OBD-II port and connect the gauge.
• Turn on the Gauge: With the gauge connected, turn on the ignition without starting the engine.
• Access the Menu: Navigate through the gauge's menu to find the "Diagnostic" or "Scan" section.
• Select the Vehicle Information: Choose the vehicle make, model, and chassis/body type accurately.
• Retrieve and Interpret the Codes: The gauge will display the fault codes. Make sure to take note of these codes for further analysis.
• Clear the Codes: After resolving the issue, use the gauge's menu to find and select the option to "Erase Codes" or "Clear Codes." This will remove the stored fault codes from the vehicle's system.

It is important to consult a qualified mechanic or a professional-grade scanner user guide for specific instructions regarding your Buick 350 model and the scanner or gauge you are using. Additionally, always make sure to address the root cause of the issue before clearing the codes to prevent them from reappearing.

Frequently asked questions