Changing The Fuel Pressure Relief Valve In A Duramax Engine

If you're experiencing issues with your Chevy or GMC Duramax, such as low fuel rail pressure or frequent change fuel filter messages, you may need to replace the fuel pressure relief valve. This valve is responsible for regulating fuel pressure in the rail, and a faulty one can cause your vehicle to go into limp mode and trigger error codes like P1093 and P0087. Before attempting any repairs, it's important to accurately diagnose the problem, as similar symptoms could be caused by other issues such as collapsing fuel lines or a failing injector. If you determine that the fuel pressure relief valve does need to be replaced, you can find aftermarket options at a third of the cost of a GM replacement, and the installation process should take around 30 minutes.

The location of the fuel pressure relief valve

The fuel pressure relief valve is located on the fuel junction block in the middle of the valley underneath the metal turbo inlet. To get to it, you will need to remove the AC compressor, thermostat housing, and turbo inlet. This will give you a good view of the fuel pressure relief valve.

In the last picture of the engine, you can see the return line tee and banjo bolt. The banjo bolt threads into the fuel pressure relief valve. To remove the valve, undo the 10mm strap holding it in place and hold it with a 24mm wrench while removing the banjo bolt in the return line tee with a 19mm wrench.

The contents of the valve are spring-loaded, so be careful when taking it apart.

How to remove the valve

To remove the fuel pressure relief valve, you will first need to locate it. The FPRV is situated on the fuel junction block in the middle of the valley underneath the metal turbo inlet. To get to it, you will need to remove the AC compressor, thermostat housing, and turbo inlet.

Once you have a clear view of the FPRV, you can begin the removal process. First, undo the 10mm strap holding the valve in place. Next, you will need to hold the FPRV with a 24mm wrench while removing the banjo bolt in the return line tee with a 19mm wrench. Be careful when removing the banjo bolt, as the contents of the FPRV are spring-loaded.

With the banjo bolt removed, you can now take the FPRV out of the fuel junction block. To do this, you will need to use a 5mm Allen wrench to loosen the valve. Again, be cautious as the spring-loaded contents may be released during this step.

Now that the FPRV is removed, you can either replace it with a new one or shim it to increase the pressure. If you choose to shim the valve, you will need two M4 washers, which can be purchased from most hardware stores. Simply place the washers inside the cap of the valve before reassembling it.

How to take the valve apart

To take the valve apart, you will need a 5mm Allen wrench and a vice, or something similar. The contents of the valve are spring-loaded, so be careful when dismantling it.

First, undo the 10mm strap holding the valve in place. Then, use a 24mm wrench to hold the valve while removing the banjo bolt in the return line tee with a 19mm wrench. Now you can start dismantling the valve. Place the valve in the vice and use the 5mm Allen wrench to unscrew the cap. Inside, you will find a spring and a ball bearing. Remove these carefully and place them to one side. You can now clean the parts and replace the spring if necessary. To reassemble the valve, simply follow these steps in reverse.

How to fix a leaking valve

If you are experiencing issues with your Chevy or GMC Duramax, such as a "change fuel filter" message, it may be due to a leaking fuel pressure relief valve. Before attempting to replace the valve, you can try diagnosing the issue by performing a "bottle test". This test will help determine if the valve is leaking and causing the problem.

• Locate the "U" shaped 3/8 hose on the driver's side fuel rail, next to the turbo.
• Remove the hose from the fuel rail and plug it.
• Attach a 3/8 hose to the fuel rail nipple and place the other end in a bottle.
• Drive the truck aggressively, with several wide-open runs.
• Check the bottle for any fuel; if there is fuel in the bottle, it confirms that the fuel pressure relief valve is leaking main pressure.

If the bottle test indicates a leaking valve, you have a few options for repair or replacement:

• Shim the valve: This involves adding washers to increase the pressure and help hold the pressure. However, this is considered a temporary solution and may not address the root cause of the leak.
• Use a "race" plug: This is a solid plug without a valve, also known as a rail plug. It is not recommended by some users as it completely blocks the relief valve.
• Replace the valve with an aftermarket option: You can find aftermarket fuel pressure relief valves from vendors online or through Duramaxtuner, which also provides instructional videos on YouTube.
• Replace with the OEM valve: You can purchase the original equipment manufacturer (OEM) valve from a dealer, with the part number #97371618, priced between $350 and $400.

Alternatively, you can try to fix a leaking valve without replacing it by tightening the packing nut or replacing the packing washer. Here are the steps:

• Locate the packing nut and use a wrench to tighten it gently.
• Check if the leak has stopped; if not, tighten the nut a little more, being careful not to overtighten, as this can damage the threads, nut, or valve.
• If tightening the packing nut does not work, proceed to replace the packing washer.
• Turn off the water supply or relevant fluid supply.
• Uninstall the handle, loosen the stem, and remove the packing nut and washer.
• Install a new, identical packing washer.
• Reassemble the system, ensuring all components are securely tightened.
• Turn on the fluid supply and check for leaks.
• If the leak persists, tighten the packing nut slightly more.
• If the leak continues, consult a professional, such as a plumber or mechanic, for further advice and assistance.

Please note that the above repair instructions for tightening the packing nut and replacing the packing washer are for a water shut-off valve. The process may differ for a fuel pressure relief valve, so consult a professional or a repair manual for specific instructions.

How to replace the valve

To replace the fuel pressure relief valve on a Duramax engine, you will first need to locate the valve. On the LB7 motor, the valve is located on the fuel junction block in the middle of the valley underneath the metal turbo inlet. To get to it, you will need to remove the AC compressor, thermostat housing, and turbo inlet.

Once you have located the valve, you will need to remove it. First, undo the 10mm strap holding it in place. Next, hold the valve with a 24mm wrench while removing the banjo bolt in the return line tee with a 19mm wrench. Be careful, as the contents of the valve are spring-loaded.

Now you can disassemble the valve. To do this, you will need a 5mm Allen wrench and a vice or similar tool. Again, be cautious of the spring-loaded contents when taking the valve apart.

After disassembling the valve, you can now reassemble it with any necessary replacements or adjustments. For example, you may need to shim the valve if it is weak. To do this, you can use two M4 washers from Ace Hardware, which fit perfectly in the cap and are roughly .030" thick each.

Finally, reinstall the valve and torque it down to the GM specification of 75 ft-lb.

Frequently asked questions