Replacing The Fuel Check Valve In A Detroit Diesel Engine

The check valve for the fuel return line for a Detroit Diesel Series 50/60 engine is located in the return line before the return line enters the tank. It is important to replace the fuel check valve as it prevents the return line from siphoning fuel out of the passages in the head. If the fuel is siphoned, the fuel pump will have to refill the passages before the injectors can function.

Location of the check valve

The check valve is an important component in a diesel engine as it stops fuel from flowing backward and prevents air intrusion. It is usually located in the return line just before the return line enters the tank.

In the case of a Detroit Diesel engine, the check valve for the fuel return line is located just before the return line enters the tank. This is contrary to what is shown in Detroit manuals and YouTube videos, which suggest that it is located on the back of the engine.

In general, check valves can be found in various locations in different vehicles. For example, in a Hummer, there are three check valves, with two of them located by the fuel tank and one by the fuel pump. In 6.2L diesel injection pumps, check valves are built into the fuel outlet that goes to the return line.

It is important to note that check valves should not be placed before the pump as this will create a restriction and cause unneeded stress on the fuel pump, leading to potential damage. The best practice is to reduce inlet restriction as much as possible when designing and installing a fuel system.

How the system works

The check valve for the fuel return line is located in the return line just before the return line enters the tank. The fuel enters the fuel filter and exits to the fuel pump. The fuel pump pulls a slight vacuum on the filter and supplies fuel up to 75 psi up to the back of the engine head.

The fuel circulates under pressure through passages in the engine head to provide fuel to the injectors. Since there is an excess of fuel supplied, the excess exits the head, restricted by a 1/16 passage and check valve to a fuel return line that ends in the fuel tank. This creates a loop, and the purpose of the check valve in the return line is to prevent the return line from siphoning all the fuel out of the passages in the head.

If the fuel is siphoned, the fuel pump has to refill the passages before the injectors have any fuel. This is a challenge for a Series 60 because the fuel pump is mechanical and only pumps if the engine is turning over.

Troubleshooting

Understanding the Fuel System:

• Familiarize yourself with the fuel system's components and their functions. The fuel check valve plays a vital role in preventing fuel from flowing backward and stopping air from entering the system.
• Know the location of the fuel check valve(s) in your specific Detroit Diesel engine model. They are typically found near the fuel tank, fuel pump, or injection pump.

Identifying Symptoms:

• Difficulty starting the engine, especially after it has been sitting for a while, could be a sign of fuel drain-back, indicating a potential issue with the fuel check valve.
• Check for fuel leaks, as they can cause air to enter the system and lead to hard-starting issues. Inspect the fuel lines, connections, and the fuel pump for any signs of leakage.
• Listen for unusual engine noises, such as knocking or pinging, which could indicate improper combustion due to fuel or exhaust gases remaining in the cylinder.
• Pay attention to the engine's performance, including reduced power, rough idling, and increased fuel consumption. These issues can result from poor exhaust flow caused by a faulty fuel check valve.

Diagnostic Steps:

• Inspect the fuel check valve and its surrounding components for any visible signs of damage or wear. Look for issues such as pitting, burning, cracking, or erosion, especially around the valve face and seat area.
• Check the valve seat for proper sealing. A poor seat can prevent a tight seal and lead to fuel leakage or airflow issues.
• Examine the fuel lines and hoses for any signs of damage or blockage. Clear any debris or buildup that could restrict fuel flow or affect valve seating.
• Measure fuel pressure and flow to ensure they are within the specified range. Low fuel pressure or restricted flow could indicate a faulty fuel check valve.
• If your engine has multiple fuel check valves, temporarily isolate each valve by clamping or disconnecting the fuel lines to determine which valve is causing the issue.

Replacing the Fuel Check Valve:

• Before replacing the fuel check valve, ensure you have the correct replacement part that matches your engine model.
• Refer to your engine's service manual or seek guidance from a certified mechanic if you are unsure about the valve replacement procedure.
• Drain the fuel from the tank or isolate the fuel lines to prevent fuel spillage during the replacement process.
• Carefully remove the old fuel check valve, taking note of its orientation and any securing mechanisms.
• Install the new fuel check valve, ensuring it is properly seated and secured in place.
• Reattach the fuel lines and any other components that were removed during the replacement process.
• Prime the fuel system by activating the fuel pump or turning the engine over without starting it to build up fuel pressure.
• Start the engine and observe its performance. Ensure there are no leaks, unusual noises, or signs of poor exhaust flow.

Preventative Maintenance:

• Regularly inspect and maintain your fuel system, including the fuel check valve, to prevent unexpected failures.
• Use high-quality fuel and periodically clean the exhaust valves and manifolds to remove carbon deposits that can affect valve seating and engine performance.
• Follow the manufacturer's recommended maintenance intervals for valve adjustments and replacements to ensure optimal engine performance and longevity.

Replacing the check valve

The check valve is an important component of your diesel engine, preventing fuel from flowing backwards and allowing air into the system. It is located in the return line just before the return line enters the tank. To replace the check valve, follow these steps:

• Remove the vanity panel: This will give you access to the fuel tank and the check valve.
• Locate the green return line: The fuel return line is usually green, and you will find it entering the fuel tank.
• Cut the return line: Before you can replace the check valve, you will need to cut the return line in an accessible place.
• Splice in a new check valve: Cut the return line and splice in a new check valve. Ensure that you install it in the correct direction, allowing fuel to flow only towards the engine.
• Secure the connections: Use appropriate fittings or clamps to secure the new check valve in place and prevent leaks.
• Refill the fuel system: Once the new check valve is installed, refill the fuel system and bleed any air from the lines.
• Test the engine: Start the engine and check for any leaks. Ensure that the engine runs smoothly and that the new check valve is functioning correctly.

It is important to note that the check valve should always be installed in an accessible location, as it may need to be replaced again in the future. Additionally, regular maintenance and inspection of the check valve can help prevent unexpected failures and keep your diesel engine running reliably.

Where to buy a new check valve

When it comes to buying a new check valve for your Detroit Diesel engine, there are a few options available to you. One popular option is to purchase the part online. Websites such as Amazon and Highway and Heavy Parts offer a range of check valves specifically for Detroit Diesel engines. These websites provide detailed information about the product specifications, customer reviews, and shipping options, making it easy to find the right part for your engine.

For example, Amazon offers a check valve for the Detroit Diesel Series 60 14L engine, which has received mixed reviews from customers. On the other hand, Highway and Heavy Parts provide a check valve for the Detroit Diesel Series 50 and Series 60 engines, manufactured to meet OEM specifications. They also offer flexible payment plans and free standard shipping on orders over $100.

Another option for purchasing a new check valve is to contact your local Detroit Diesel dealer or authorized service center. They will have access to genuine parts and can provide expert advice to ensure you get the correct part for your specific engine. It is always recommended to consult with a professional before attempting any repairs or replacements on your engine.

Finally, you may also be able to find check valves at your local auto parts store. However, it is important to ensure that you are purchasing a compatible part for your Detroit Diesel engine, as not all stores may carry the specific valve you need. It is always a good idea to call ahead and check availability before making a trip to the store.

Frequently asked questions