Deleting Fuel Filter: More Rail Pressure For Duramax?

Deleting the factory fuel filter on a Duramax engine after installing an aftermarket lift pump, such as a FASS or AirDog, is a modification that some owners choose to perform. The rationale behind this modification is to remove any unnecessary restrictions in the fuel system and improve fuel flow. However, there are differing opinions on whether deleting the factory fuel filter is beneficial or detrimental.

Those in favour of deleting the factory fuel filter argue that it removes a potential restriction in the fuel system, which may improve fuel flow and engine performance. Additionally, they suggest that the aftermarket lift pump and its filters are sufficient to ensure proper fuel filtration, rendering the factory fuel filter redundant. Some also mention the aesthetic benefit of a cleaner-looking engine bay after removing the factory fuel filter assembly.

On the other hand, those opposed to deleting the factory fuel filter argue that it provides additional filtration and a layer of protection for the engine. They believe that the factory fuel filter can catch any contaminants that the aftermarket filters might miss. Keeping the factory fuel filter also allows for a primary and secondary filtration system, which can extend the life of all filters. Additionally, the factory fuel filter assembly includes a priming mechanism, which can be useful if the aftermarket lift pump fails.

It is important to note that deleting the factory fuel filter may require additional modifications, such as installing a bypass adapter or a fuel filter delete bowl. Some owners have also reported issues with leaks and hard starting after performing this modification. Therefore, it is recommended to thoroughly research and understand the potential benefits and risks before making any modifications to the fuel system.

The factory fuel filter is prone to leaks

One user reported that they had to pull vacuum from the fuel test port to prime their truck when their FASS (Fuel Air Separation System) failed. They suggested that if your lift pump fails, you will need to do the same or call a tow truck. They also mentioned that the FASS filters work very well and are like 3-micron filters, but they are considering putting a 2-micron CAT filter back in line to catch anything before the lift pump as they are cheap to change.

Another user reported that they had to reinstall the factory filter after removing it because their truck would not start without it. They also mentioned that they constantly get a "change fuel filter" error on their dashboard, which they are guessing can be bypassed by shorting some pins in the sensor.

A different user reported that they had to remove a check ball from the stock filter head for the elimination bowl to work properly. They "learned that one the hard way."

One user suggested that if you are going to remove the factory filter, you should use a piece of leftover hose and loop it back on itself rather than using a short piece of hose, as the short piece will collapse. They also mentioned that you will lose your primer and that if your lift pump fails, you will have trouble getting your truck running again.

In summary, while some users have reported success in removing the factory fuel filter, others have encountered issues such as leaks, priming problems, and error messages. It is important to carefully consider the potential risks and benefits before deciding whether or not to remove the factory fuel filter.

The stock filter is restrictive when turned off

The stock filter is also prone to leaks. The efficiency rating @ X microns makes a big difference. Would you rather have a 2-3 micron rating at 95%? Or a 4-micron rating at 99.9%?

If you delete the stock filter, you will lose the ability to prime your engine if and when the FASS or AirDog pump quits. Nicktane makes an adapter that leaves the head intact and just deletes the factory fuel filter. They also make an adapter to put a different filter on the factory filter head.

One benefit of keeping the factory fuel filter is that you can rotate new fuel filters. The filters actually filter a little better if they are a little "dirty", i.e. used. So if you change the fuel filters on the lift pump when you do this oil change and then change the factory fuel filter with the next oil change, you will always have the benefit of one fuel filter that is working optimally since it is not brand new and clean.

The stock filter is not restricting anything with a 165GPH pump supplying it

One user on the Duramax Forum noted that they had seen reports of factory fuel filters getting restricted to the point of collapsing. However, they also stated that, from their personal findings, fuel flow from the CP4 pump was helped very little, if at all, by deleting the stock filter. This suggests that there may be minimal gains in fuel flow by removing the stock filter, but it is not a significant restriction with a 165GPH pump supplying it.

Another user on the same forum noted that they had deleted their stock fuel filter with a FASS pump installed and had not experienced any problems. They also mentioned that the dash indicated 0% fuel filter usage, but they would reset it occasionally as a precaution.

Some users on the Duramax Forum and Diesel Place Forum have also mentioned that deleting the stock fuel filter can make the engine bay look cleaner and remove the need to change an expensive filter. However, it is important to note that deleting the stock fuel filter will result in the loss of the primer, and if the lift pump fails, it may be difficult to get the truck running again.

Overall, while there may be minimal gains in fuel flow by deleting the stock filter, it is not a significant restriction with a 165GPH pump supplying it. The decision to delete the stock filter should be made after considering the potential benefits and drawbacks, including the loss of the primer function.

The stock filter can be used to prime the fuel system in case of a lift pump failure

However, some people choose to delete the factory fuel filter, especially after installing an aftermarket lift pump such as a FASS or Airdog. Deleting the factory fuel filter can remove a potential source of leaks and restrictions in the fuel system, and reduce maintenance costs by eliminating the need to replace the factory filter.

There are a few ways to delete the factory fuel filter. One way is to use a fuel filter delete bowl, which removes the factory filter but retains the water-in-fuel sensor, fuel heater, and primer bulb. Another way is to bypass the factory filter by routing the fuel lines directly to the CP3 intake fuel lines. This can be done using a bypass adapter or by looping a short piece of hose between the two fuel lines.

It is important to note that deleting the factory fuel filter removes the ability to prime the fuel system manually, so if the lift pump fails, it may be more difficult to get the truck running again. Additionally, the factory fuel filter provides additional filtration and can help protect the CP3 injection pump and injectors by catching any contaminants that may have passed through the lift pump filters.

Overall, the decision to keep or delete the factory fuel filter depends on various factors, including the condition of the filter, the demand on the fuel system, and personal preferences for maintenance, reliability, and cost.

The stock filter is one of the better water separators

Some people choose to remove the stock filter because they believe it is redundant and restricts fuel flow. However, the restriction is negligible, and the benefits of the additional filtration and protection against water contamination outweigh any potential gains from removing the stock filter.

In addition, the stock filter can be used to prime the fuel system in the event of a lift pump failure. While some people believe that this is unnecessary, as a failed lift pump will prevent the engine from running regardless, others argue that it is a good idea to keep the stock filter as a backup in case of an emergency.

Overall, the stock filter provides valuable additional filtration and protection against water contamination, and there are few, if any, benefits to be gained from removing it.

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