Aligning Gmc Acadia's High-Pressure Fuel Pump: Step-By-Step Guide

If you're experiencing problems with your GMC Acadia's high-pressure fuel pump, you're not alone. Several Acadia owners have reported issues such as low fuel pressure, white smoke, and engine hesitation. While there can be several causes for these problems, one common solution is to replace the high-pressure fuel pump. However, even after replacing the pump, some owners have continued to experience issues. This suggests that the problem may lie elsewhere, such as with the follower, the camshaft lobe, or even a cracked camshaft. To diagnose the issue, it's recommended to conduct tests such as measuring fuel pressure with the engine running or monitoring it electronically with a scan tool. With the right tools and knowledge, you can get your GMC Acadia's fuel pump running smoothly again.

Fuel pump cam lobe alignment

To align the fuel pump cam lobe of a GMC Acadia, you need to ensure that the cam lobe is properly aligned with the roller lifter. This is important because the cam lobe's position relative to the roller lifter affects the fuel pump's ability to build pressure.

• Remove the high-pressure fuel pump: Before attempting any repairs or adjustments, it is necessary to remove the high-pressure fuel pump from the engine. This provides access to the fuel pump cam lobe and other relevant components.
• Inspect the camshaft and cam lobe: With the fuel pump removed, carefully inspect the camshaft and cam lobe for any signs of damage or abnormal wear. Ensure that the cam lobe is intact and not broken, as this could affect its ability to engage with the roller lifter properly.
• Check the roller lifter: Verify that the roller lifter is in place and in good condition. The roller lifter should be positioned correctly to follow the cam lobe as the camshaft rotates.
• Align the cam lobe with the roller lifter: To ensure proper alignment, the cam lobe should be at its lowest point relative to the roller lifter. This alignment ensures that the roller lifter is in the correct position to engage with the cam lobe during the camshaft's rotation.
• Reinstall the high-pressure fuel pump: Once you have confirmed that the cam lobe and roller lifter are properly aligned, carefully reinstall the high-pressure fuel pump, ensuring that all components are secure and properly connected.
• Test the fuel pump: After reassembly, test the fuel pump to ensure it is functioning correctly. You can do this by monitoring fuel pressure with a scan tool or physically measuring it at the test port on the fuel rail.

It is important to note that fuel pump cam lobe alignment is just one aspect of fuel pump maintenance and repair. Other factors, such as internal pump issues, wiring problems, or a faulty fuel pressure sensor, can also contribute to fuel pump malfunctions. It is always recommended to consult a qualified mechanic or refer to the manufacturer's guidelines for specific instructions related to your vehicle.

Testing the fuel pump

To test the fuel pump on a GMC Acadia, you can either physically measure the fuel pressure with the engine running or monitor it electronically with a scan tool.

Physically Measuring Fuel Pressure

The first method involves locating the test port on the fuel rail. This is where you will physically measure the fuel pressure. With the engine running, you can expect to see a pressure of around 500 psi or higher. If the pressure drops below this threshold, it indicates an issue with the fuel pump.

Monitoring Electronically with a Scan Tool

The second method involves using a scan tool to monitor the fuel pump electronically. This tool will display the actual fuel rail pressure and compare it to the desired pressure. If the actual pressure is significantly lower than the desired pressure, it suggests a problem with the fuel pump or another component in the fuel system.

Additional Testing Procedures

In some cases, you may need to remove the pump from the vehicle and perform a bench test. This is usually done if the initial tests indicate a potential issue with the fuel pump but further confirmation is required. Additionally, if you suspect an issue with the high-pressure fuel pump, it is worth checking the camshaft and roller lifter for any signs of damage or malfunction.

Common Issues and Symptoms

Some common issues with the high-pressure fuel pump include internal pump problems, follower issues, or camshaft lobe-related problems. Symptoms of a faulty fuel pump can include white smoke from the engine, long crank times, and hesitating or stalling during driving. Furthermore, specific error codes, such as P0090 or P069E, can indicate potential issues with the fuel pump or related components.

Troubleshooting low fuel pressure

If you are experiencing low fuel pressure in your GMC Acadia, there are several troubleshooting steps you can take to try and identify and resolve the issue.

Firstly, it is important to determine if the issue is with the high-pressure fuel pump or the in-tank (low-pressure) fuel pump. The high-pressure pump is a mechanical pump, so the issue could be internal, or related to the follower or the camshaft lobe. The camshaft lobe must be aligned properly for the pump to function correctly. If the camshaft is cracked, it may spin the high-pressure pump lobe until it meets resistance from the roller lifter, and then stop spinning.

To test the high-pressure pump, you can use a scantool to monitor fuel rail pressure. You are looking for a reading of at least 500 psi. Alternatively, there should be a test port on the fuel rail where you can physically measure the fuel pressure with the engine running.

If the high-pressure pump appears to be functioning correctly, the issue may lie with the in-tank fuel pump. To test this pump, you will need to connect a fuel pressure tester to the low-pressure feed line, with the key on and the engine off. You are looking for a pressure of 56-62 psi, which should not decrease by more than 5 psi in one minute.

If you find that the in-tank fuel pump is not functioning correctly, you may need to replace it. However, if you replace the pump and the issue persists, the problem could be related to the fuel pump control module (FPCM). This can be diagnosed by checking for issues with the FPCM wiring harness.

Fuel pump replacement

Step 1: Testing the Fuel Pump

Before replacing the fuel pump, it is important to test whether it is faulty. Park your vehicle on a firm, level surface and engage the parking brake. Locate the fuel pump, which is usually in the fuel tank. Open the fuel cap and turn the key to the "ON" position. Listen at the filler opening; a properly functioning fuel pump will produce a hum for two to three seconds. If no sound is heard, the pump may need to be replaced.

Step 2: Checking the Fuse and Relay

Next, find and verify the fuel pump fuse and relay. If the fuse is blown, replace it with one of the same amperage. If the fuse and relay are functional, check for power and ground at the fuel pump. If there is power and ground at the pump, then it is faulty and should be replaced.

Step 3: Preparing for Replacement

Before beginning the replacement process, relieve the fuel system pressure by disconnecting the negative battery cable. Siphon or drain as much fuel as possible from the fuel tank to reduce the risk of spills. Disconnect the filler tube hose and the electrical connection to the pump.

Step 4: Removing the Fuel Tank

Support the fuel tank with a jack and a block of wood. Remove any retaining straps or bolts holding the tank to the frame and carefully lower it.

Step 5: Replacing the Fuel Pump

Disconnect the fuel lines and remove the old fuel pump from the tank. Compare the new fuel pump with the original to ensure you have the correct part. Install the new fuel pump, reconnecting the fuel lines and any retaining straps.

Step 6: Reassembling the System

Reconnect the filler tube hose and the electrical connector. Reconnect the negative battery cable and fill the tank with fuel. Conduct a road test to confirm that the new fuel pump is functioning properly.

Additional Tips:

• Work in a well-ventilated area to minimize the risk of fire and inhalation of harmful fumes.
• Always wear safety glasses, gloves, and appropriate clothing to protect against fuel spills and splashes.
• Clean around the fuel pump before removal to prevent dirt and debris from falling into the fuel tank.
• Consider replacing related components such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.

Alignment of High-Pressure Fuel Pump in GMC Acadia

When installing a high-pressure fuel pump in a GMC Acadia, proper alignment of the fuel pump cam lobe is crucial. Ensure that the roller follower is in place and that the cam lobe is at its lowest point. If the roller does not slide easily into the key slot, do not force it, as there may be an issue with the camshaft.

Testing High-Pressure Fuel Pump in GMC Acadia

To test the high-pressure fuel pump on a GMC Acadia, you can either physically measure the fuel pressure using a test port on the fuel rail with the engine running or monitor it electronically with a scan tool. A functioning pump should maintain a pressure of at least 500 psi.

Fuel injectors

To avoid these issues, it's crucial to maintain your Acadia's fuel injectors properly. Regular cleaning and inspection can help prevent carbon buildup and ensure optimal performance. Additionally, using high-quality fuel and regular engine maintenance can contribute to the longevity of your fuel injectors.

If you suspect issues with your fuel injectors, it's essential to have them diagnosed and addressed promptly by a qualified technician. Driving with faulty injectors can lead to further complications and potentially costly repairs. In some cases, fuel injector issues may be covered under your vehicle's warranty or federal emissions policies, so it's worth consulting your dealer or a trusted mechanic.

Frequently asked questions