Changing Cummins Fuel Filters: Step-By-Step Guide

Changing the FASS fuel filters on a Cummins engine can be a tricky task, and it is important to do it correctly to avoid damaging your engine. The process may vary depending on the model of your Cummins engine and FASS pump, but there are some general steps and tips that can be followed. It is recommended to refer to the FASS instruction manual or contact their technical support for specific instructions on how to change the filters. Additionally, it is important to prime the system correctly and bleed the air out of the fuel system to ensure the engine starts and runs smoothly after the filter change.

Draining the filters

Locate the Drains: Start by locating the drain valves at the bottom of the fuel filters. These valves are typically positioned directly underneath the filters and are responsible for releasing the accumulated water and contaminants.

Prepare for Draining: Place a suitable container or drain pan underneath the drain valves to collect the drained fluid. This fluid will be a mixture of fuel, water, and contaminants, so ensure you have an appropriate receptacle to capture it.

Open the Drains: Using the appropriate tool, usually a wrench or a screwdriver, carefully open the drain valves. Depending on your Cummins model, you might have to loosen or unscrew the valves. Be cautious not to strip the threads or damage the valves during this process.

Allow Fluid to Drain: Once the drains are open, let the fluid flow freely into the container. This process might take a few minutes, depending on the amount of fluid and contaminants built up in the filters. Ensure that your container has sufficient capacity to capture all the drained fluid.

Monitor the Draining Process: Keep an eye on the draining fluid to ensure it flows smoothly and doesn't back up. If the fluid level rises in the container and starts to approach the filter, stop the draining process and empty the container to prevent overflow.

Close the Drains: After the fluid has finished draining and you've emptied the container, carefully close the drain valves. Ensure that the valves are securely tightened to prevent any leaks or further drainage.

By following these steps, you will effectively drain the FASS fuel filters on your Cummins engine. Remember to dispose of the drained fluid properly and in accordance with local regulations. Always refer to your Cummins service manual or seek advice from a qualified diesel technician if you have any questions or concerns during the filter draining or changing process.

Priming the system

To prime the system, you must first fill the filters with diesel. Spin on the new filters, tightening the water separator and leaving the fuel filter a tick loose. Set your truck in prime mode and wait for the fuel to fill the filter. You should be able to hear it filling. Once the filter is full, tighten it up.

FASS sells their kits with an instruction manual, which may be a more legal-friendly way to prime the system. You can also refer to the FASS website for the owner's manual.

If you have air in the fuel system, loosen the filter, bump the starter and check if fuel is coming out. If not, bleed the air at the engine and try again. You can also loosen the return bolt on the vp and use a jumper wire on the relay for the FASS to run it, with the key in the 'on' position.

Filling the filters with diesel

To fill the filters with diesel, start by tightening the water separator and leaving the fuel filter a little loose. Set your truck in prime mode and listen for the sound of the fuel filling the filter. Once you hear the fuel filling up the filter and reaching the top, tighten the fuel filter. It is important to keep your face away from the filter during this process, as there may be some splashing or overflow.

FASS also provides instruction manuals and technical support on their website, which can be helpful if you are unsure about the process or have never changed the FASS fuel filters before. It is recommended to refer to these resources before beginning the filter change.

Additionally, when filling the filters with diesel, make sure to only use fuel that is free of contaminants. This is because the purpose of the fuel filters is to remove impurities from the fuel before it reaches the engine. Using clean diesel fuel will help ensure that your filters last longer and perform optimally.

By following these steps and taking the necessary precautions, you can effectively fill the FASS fuel filters with diesel and ensure the smooth operation of your Cummins engine.

Tightening the water separator

To tighten the water separator when changing your FASS fuel filters on a Cummins engine, follow these steps:

Firstly, tighten the water separator by hand. Ensure that it is securely fastened, but do not overtighten it. Next, hand-tighten the fuel filter, but leave it a little loose. Set your truck in prime mode and listen for the sound of the fuel filling the filter. As the filter fills, the pump tone will change, indicating that the gear now has fuel. Once the filter is almost full, tighten it up.

It is important to note that you should keep your face away from the filter during the priming process, as there is a risk of fuel spray if you are too close. Additionally, the FASS kit comes with an instruction manual that provides a detailed, step-by-step guide on how to change the filters, so it is recommended to refer to that as well.

Loosening the injector lines

Before beginning, make sure you have the necessary tools, including a wrench or a 17mm crowfoot wrench and a ratchet. It is also recommended to have a helper nearby to assist with cranking the engine.

First, locate the injector lines. For Cummins engines, you will typically need to loosen the 1st, 3rd, and 4th injector lines. These lines are where the injectors connect to the engine block.

Next, use your wrench to loosen each of the selected injector lines. Be careful not to remove them completely, just loosen them enough so that fuel can escape. Have a rag or container ready to catch any spilling fuel.

Once the injector lines are loosened, have your helper crank the engine for about 10 seconds at a time. You will need to do this multiple times until you see solid fuel squirting out of the lines. This process may take several minutes, so be patient.

After you have achieved a solid stream of fuel with no air bubbles, tighten the injector lines back up. Be careful not to over-tighten them, as this can cause damage.

Finally, attempt to start the engine. It may run rough for about 30 seconds as the air is fully purged from the system, but it should eventually smooth out.

If you are still having issues with air in the fuel system, you may need to repeat the process or check for leaks elsewhere in the system. Additionally, make sure that you are filling the fuel filters with diesel before installing them, as this can also cause airlock issues.

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