Replacing The Fuel Pressure Sensor: Diy Guide

The fuel pressure sensor in a Chevy or GMC Duramax diesel engine can cause problems with engine performance if it malfunctions. The sensor is located on the rear of the fuel rail on the passenger side of the engine compartment, near the firewall. To replace it, you will need to remove the air intake tube to access the sensor more easily. Then, disconnect the sensor and plug in the male fuel pressure plug into the truck's wiring harness. Finally, ensure all connections are tight and gently tug on them to make sure they are secure.

Check for low fuel pressure

To check for low fuel pressure, look out for the following symptoms:

• Engine power loss: If your engine struggles with high-load situations, such as sudden acceleration or climbing a hill, it may be due to low fuel pressure.
• Difficulty starting: If your engine is cranking but not starting, low fuel pressure could be the culprit.
• Engine popping at high speeds: If your engine sputters at high speeds, it may indicate that the fuel pump is unable to supply a constant stream of fuel at the required pressure.
• Unresponsive throttle: Lag in your car's pickup can be a sign of low fuel pressure.
• Stalling engine: If your engine stalls while running or idling, it could be due to fluctuations or sudden drops in fuel pressure.
• Check engine light: Modern cars have a fuel pressure sensor that can indicate low fuel pressure. A check engine light often comes on with a P0190 code.
• Turbo lag: If you have a turbocharger and it's taking longer than usual to spool, it could be a sign of low fuel pressure.

If you suspect low fuel pressure, you can perform a few checks before seeking professional help:

• Listen for the fuel pump: Turn the key from the OFF to the ON position. If you don't hear the fuel pump buzzing, it may need replacement.
• Check fuel pump delivery: Locate the OUTPUT port of the fuel pump, usually connected to the fuel filter. Disconnect the hose and block the passage with your finger. Start the car, and if you don't feel strong fuel pressure, the pump may need replacement.
• Inspect the fuel filter: A clogged fuel filter can cause low fuel pressure. Check if it's due for a replacement.
• Check fuel pipelines: Inspect the fuel lines for any damage or leaks, especially if you've been driving on bumpy roads or off-road.
• Use a fuel pressure tester: You can connect a fuel pressure tester to the Schrader valve fitting on the fuel rail. Turn the ignition on and check the psi reading. Compare it to the recommended pressure for your vehicle.

Install a shim kit

To install a shim kit for the fuel pressure sensor on an LLY Duramax engine, follow these steps:

First, purchase a suitable shim kit. This will cost around \$12. You will also need a range of tools, including various sockets and wrenches, a vice or vice grips, a small punch, and a c-clamp. You may also want to use some paper towels or newspaper to protect parts of the engine.

Begin by locating the Glow Plug Controller. Use a 10mm socket to loosen the left-side bolt, and a 10mm end wrench to loosen the right side. Then, move the box to one side and remove the bracket underneath using a 12mm socket and 10mm bolt. With the bracket removed, you will now be able to see the Fuel Rail.

On the end of the Fuel Rail, you will see what appears to be a nut; this is the Pressure Valve. Use an 18mm wrench, and another wrench for leverage, to remove this. Be careful not to damage the O-ring. Once removed, the valve should have a spring and a plate with three holes inside. Thread the supplied nut onto the valve, then use an adjustable wrench to thread the nut towards the vice/vice grips to separate the fuel valve.

Now, take the three washers from the kit and place them inside, under where the spring will go. Place the spring on top of the washers, then the plate, and then the end cap. Use a piece of thick paper or cardboard on the end cap to protect it, then use a c-clamp to push it all back together. Make sure it is lined up straight. Tap the three spots back into place with a small punch.

Finally, thread the valve back into the Fuel Rail and tighten it. Replace the bracket and the Glow Plug Controller, ensuring all bolts are tight. Your truck may take a couple of attempts to start as you have introduced air into the fuel system.

Note that some sources suggest that installing a lift pump or a PPE race FPRV is a more reliable solution than a shim kit.

Change the fuel filter

To change the fuel filter on an LLY Duramax engine, follow these steps:

First, locate the fuel pressure sensor. It is usually found near the firewall, behind the intake tube on the passenger side of the engine compartment. You may need to remove the air intake tube to access it more easily.

Once you have located the fuel filter, place a drain pan or container underneath it to catch any spilled fuel. Then, disconnect the fuel lines from the filter. Be sure to relieve the fuel system pressure and absorb any spilled fuel with a rag before proceeding.

Next, remove the old fuel filter by unscrewing it from the mounting bracket. You may need to use a filter wrench to loosen it. Take note of the direction of the fuel flow arrow on the filter, as the new filter must be installed in the same direction.

Before installing the new fuel filter, inspect the O-rings on the filter housing for any damage and replace them if necessary. Clean the mounting surface and ensure it is free of debris.

Install the new fuel filter by screwing it into the mounting bracket, ensuring that the fuel flow arrow is pointing in the correct direction. Tighten the filter securely, but be careful not to overtighten it.

Finally, reconnect the fuel lines to the new fuel filter, making sure all connections are secure. Start the engine and check for any leaks.

It is recommended to replace the fuel filter regularly as part of routine maintenance to ensure optimal engine performance and fuel efficiency.

Monitor demand vs actual fuel rail pressure

Monitoring the demand versus the actual fuel rail pressure is an important diagnostic tool for your Chevy Duramax LLY engine. This can be done using a device like the Edge CTS, which will allow you to see if there is a discrepancy between the desired and actual fuel rail pressure. This can help you identify issues with your fuel system, such as a faulty fuel pressure relief valve or injectors returning too much fuel.

If you notice that your engine is not performing as expected, especially when under load or at higher temperatures, monitoring the demand versus actual fuel rail pressure can help you identify the cause. This can include issues such as low fuel pressure, which can be addressed by installing a shim kit or a lift pump. It may also be worth checking the age of your fuel filter and considering a replacement if it has been a while since the last change.

Additionally, monitoring fuel rail pressure can help diagnose issues with your injectors. If they are returning too much fuel, it can cause the fuel pump to struggle to keep up with demand, resulting in reduced engine performance. In some cases, you may need to replace the injectors to resolve the issue.

By regularly monitoring the demand versus actual fuel rail pressure and addressing any discrepancies, you can help ensure that your Chevy Duramax LLY engine is running optimally and prevent potential issues from occurring.

Check for a collapsed or kinked fuel line

To check for a collapsed or kinked fuel line, you will need to inspect the rubber portion of the fuel supply (suction) lines. The rubber section of the line could become kinked or collapse, causing a fuel system restriction (high vacuum gauge readings) or fault codes such as P0087, P0093, and/or P1093.

To inspect the fuel lines for kinks or collapse, carefully cut, split, and remove the OEM crimp from both ends of the flexible hose. You can use a small cut-off wheel to make these cuts. Be very careful not to damage the flare on the end of the steel pipe that will be reused. Once the OEM crimps and flexible portion of the hose are removed, you can inspect the hose for any signs of collapse or kinking. If the hose is damaged, it should be replaced.

If you are experiencing low fuel pressure or fuel system restriction, it is recommended to replace the rubber section of the fuel supply line with a 1/2 ID hose meeting SAE specification 100R3. The replacement hose would be a 1/2" diameter Parker part number 601-8 or H017-8. Use worm-type hose clamps (double clamps on each end) to attach the new hose to the existing pipe.

Frequently asked questions