Priming C7 Cat Fuel Filters: Steps To Success

Changing the fuel filter on a Cat C7 engine can be a tricky process. The first step is to determine whether the engine has one or two fuel filters. If it has two, it is recommended to change them one at a time, starting with the primary filter. It is also important to ensure that the fuel tank is full or nearly full, and to park the vehicle so that the fuel tank is uphill from the filters. This will help prevent fuel from siphoning back into the tank when the filter is removed.

When it comes to priming the new filter, there is some debate among experts. Some recommend pre-filling the filter with diesel fuel, while others suggest using a primer pump or pressurizing the fuel tank. It is generally advised to avoid pre-filling the filter if there is no primer pump, as this can introduce unfiltered fuel into the system. Instead, one should slowly fill the small outer holes of the filter, which are the inlets, while being careful not to get any fuel in the center hole, which is the outlet.

If the engine has a manual primer pump, the manufacturer's instructions should be followed for priming. If there is no primer pump, one may need to be installed, or alternative methods such as pressurizing the fuel tank or pulling a vacuum on the return fuel line may be necessary to prime the system.

Filling the fuel filter

Before filling the fuel filter, it is important to gather the necessary tools and equipment. This includes a filter wrench of the correct size for your specific model, an oil filter wrench (optional), and a pan or bucket to catch any spilled fuel. Having the correct size filter wrench is essential to avoid damaging the filter during removal or installation.

Now, let's get into the step-by-step process of filling the fuel filter:

• Remove the intake: To create more room for the filter to be taken out, it is recommended to remove the intake first. Carefully loosen and remove the intake using the appropriate wrench or tool. Be cautious to avoid damaging any surrounding components.
• Open the filter: Using the correctly sized filter wrench, position it around the filter and turn it counterclockwise to open it. Apply steady pressure to loosen the filter. Once loosened, remove the filter by hand. If needed, an oil filter wrench can be used for a better grip and easier removal.
• Drain the old filter: Before installing the new filter, ensure that the old one is completely drained of fuel. Hold the open end of the filter facing downwards and let the fuel drain into the pan or bucket. Properly dispose of the old filter and any spilled fuel.
• Prepare the new filter: Take the new fuel filter and identify the small outer holes, which are the filter inlets, and the centre hole, which is the outlet. If your CAT C7 has a manual primer pump, you can fill the filter with clean diesel fuel. Slowly fill the outer holes with fuel, being careful not to get any in the centre hole. If your engine does not have a manual primer pump, Caterpillar's official recommendation is to install the filter dry. However, some users suggest filling the filter with injector cleaner or diesel.
• Plug the filter: If you are filling the filter, once it is full, clean up any spilled fuel and reinstall the plug. Ensure that the air is able to vent from the plug during the filling process.

Remember, it is important not to pre-fill the filter with fuel or oil as it can cause contaminated or unfiltered fuel to enter sensitive engine components. Instead, lubricate the O-ring on the filter with a small amount of oil before installing it.

Removing air from the system

To remove air from the system, you can try the following methods:

• Filling the fuel filter with injector cleaner, diesel, or filtered fuel.
• Turning the key in the ignition to allow the fuel pump to prime itself.
• Bleeding air from the system by loosening or removing the bleed screw on the fuel filter housing.
• Using an electric fuel priming pump or manual hand pump to prime the system.
• Pressurizing the fuel tank using an air compressor with a few pounds of pressure and loosening the fuel line at the HEUI pump to allow fuel flow.
• Pulling a vacuum on the return fuel hose using a vacuum brake bleeder and an air compressor.
• Installing a manual primer pump on the secondary fuel filter.
• Keeping the fuel tank full or nearly full, and parking the vehicle so that the fuel tank is uphill from the filters.
• Following the CAT book instructions for changing the fuel filter, including using the correct plug and ensuring proper venting during filling.
• Cycling the ignition key several times to run the lift pump on the fuel pump for approximately one minute.

Using a hand primer

To prime a C7 CAT engine after changing the fuel filters, you can use a hand primer. Here is a step-by-step guide:

Step 1: Locate the Hand Primer

Firstly, locate the hand primer pump on your engine. On some C7 CAT engines, the hand primer pump may be installed on the water separator. If your engine did not come with a hand primer pump from the factory, you can purchase one and install it. The installation process typically involves removing a cover plate and mounting the pump.

Step 2: Prepare the New Fuel Filter

Before priming, prepare your new fuel filter. Obtain a clean plastic plug, such as one from a hydraulic line, and use it to plug the center hole of the new fuel filter. This step is crucial to ensure that only filtered fuel enters the engine.

Step 3: Fill the New Fuel Filter

Now, slowly fill the new fuel filter with clean diesel fuel. Pour the fuel into the smaller holes around the edge of the filter, being careful not to get any fuel in the center hole. This process ensures that the fuel is properly filtered before entering the engine.

Step 4: Install the New Fuel Filter

Once the new fuel filter is filled, carefully install it onto the engine. Make sure to tighten it securely, following the manufacturer's instructions or recommendations from a certified mechanic.

Step 5: Prime the Fuel System

With the new fuel filter installed, it's time to prime the fuel system. Depending on your specific engine configuration, you may need to open the bleed screw to allow air to escape. Start the engine and let it run, allowing the fuel pump to fill the filter. You may need to repeat this process a few times to ensure the system is fully primed.

Step 6: Check for Leaks and Spills

After priming, carefully inspect the fuel system for any leaks or spilled fuel. Clean up any spilled fuel immediately and ensure that all connections are secure and tight.

Step 7: Start the Engine and Monitor Performance

Finally, start the engine and let it idle. Observe the engine's performance, ensuring that it operates smoothly. If the engine runs smoothly, you have successfully primed the C7 CAT after changing the fuel filters using a hand primer.

It is important to note that some people choose to prefill the fuel filters with diesel or injector cleaner before installation. However, this practice is strongly discouraged by experts, as it can allow unfiltered fuel to enter the engine, potentially causing damage. Always follow the recommended procedure provided by the manufacturer or a certified mechanic.

Using an electric fuel priming pump

If your C7 is equipped with an electric fuel priming pump, you can prime the fuel system by following these steps:

• Locate the fuel priming pump: The fuel priming pump on the C7 is usually located near the secondary fuel filter.
• Open the fuel priming pump: Before operating the pump, make sure that the fuel lines at the fuel manifold are not loosened, as this may cause damage to the fittings and a loss of priming pressure.
• Operate the fuel priming pump: Pump the handle until you feel strong pressure. This may require several strokes. Then, lock the fuel priming pump.
• Crank the engine: Do not crank the engine continuously for more than 30 seconds. If the engine has been cranked for 30 seconds without starting, allow the starting motor to cool for two minutes before trying again.
• Start the engine: If the engine runs rough, operate it at low idle. Do not raise the engine RPM until it operates smoothly.
• Repeat if necessary: If the engine does not start, open the fuel priming pump and repeat steps 3 and 4.

It is important to note that some sources recommend against pre-filling the fuel filters, as it allows unfiltered fuel to pass through the system. Instead, they suggest using an electric fuel priming pump or a manual hand pump to prime the system.

Bleeding the entire fuel system

Step 1: Prepare the Work Area

Before beginning any work, it is important to ensure that the area around the fuel system is clean and free of dirt or debris. Any dirt entering the fuel system can cause significant issues. Cover any disconnected fuel system components with a suitable cover to prevent contamination.

Step 2: Locate the Fuel Filter Plug

Identify the fuel filter base and ensure it is equipped with a plug. The fuel filter plug is usually located near the secondary fuel filter.

Step 3: Remove the Plug and Fill the Filter

Remove the plug, being careful to avoid letting dirt enter the fuel system. Use clean fuel to fill the filter, ensuring that air can vent from the plug during this process. It is recommended to fill the filter through the outside holes rather than down the center to ensure proper filtration.

Step 4: Reinstall the Plug and Clean Up

Once the filter is full, clean up any spilled fuel and reinstall the plug. Ensure that the plug is securely tightened to prevent leaks.

Step 5: Start the Engine and Operate at Low Idle

After reinstalling the plug, start the engine. If the engine runs rough, continue to operate it at a low idle. Do not increase the engine RPM until it runs smoothly. This process may take several minutes, and it is important to be patient and allow the engine to stabilize.

Step 6: Address Any Issues

If the engine does not start, you may need to repeat the priming process. Open the fuel priming pump and operate it until strong pressure is felt, then lock the pump and try starting the engine again. Do not crank the engine continuously for more than 30 seconds, and allow the starting motor to cool for two minutes between attempts.

By following these steps, you will effectively bleed the entire fuel system of your C7 CAT engine, ensuring that clean, filtered fuel is delivered to the engine for optimal performance.

Frequently asked questions