2017-2024 L5P Duramax Dual Fuel Filter Kit by VSE Engineering

This system replaces your single L5P fuel / water filter with a direct plug and play style filtration system that takes advantage of the benefits and control of the FACTORY L5P lift pump system.

What are we replacing? The stock system contains a water / fuel filter combo that filters down to 5 micron max using the same fuel filter that is used on the Chevy Cruise 1.8L Motor. Ours contains 2 filters. A Pre filter that is a water separator with a change interval of 15,000 + miles that filters out larger debris with 18% more surface area than the stock filter and filters at a 95% efficiency at 13 micron and a post filter to catch all the fine debris that filters down to 3 micron at a 99% efficiency, with a change interval of 15,000+ miles.

Why did we invent this ? Being predominantly an engineering and calibration development company, and after tuning thousands of L5P Duramax trucks (and 10s of thousands of other common rail turbo diesels that experience fuel system failures), we began to realize that the HP4 (the L5P high pressure fuel pump) and the injection system of the L5P, while robust, is built with extremely tight tolerance and does not do very well when debris around 5 micron or ANY LEVEL of water are passed through the factory fuel/water filter. We found that the factory L5P lift pump to be very consistent at delivery of a very high volume of fuel under loaded conditions, and when the filter experiences enough debris and water that it ended up getting pushed through the filter into the fuel system under the large differential pressure exerted across the factory filter. What the L5P REALLY NEEDED was a post filter AND a dedicated water filter. That is exactly what we made – except we went 1 critical step farther, we machined the system to be lower in tested differential pressure across the assembly than the factory which means it can support HIGHER fuel flow volume (higher horsepower) at a higher filtration efficiency than the factory single (and other single replacement) fuel filters.  – Take it from us, we have tested this system under the most extreme conditions with purpose.

Is this a lift pump it looks like one? No the L5P runs a 3 phase brushless variable speed lift pump that is mounted in the fuel tank submerged by a volume of fuel to retain, at all times, positive head pressure over the top of the discharge volume of fuel. This lift pump is controlled by a fuel pump driver module located above the spare tire in truck models that reports to the ECM and handles low pressure fuel pressure monitoring. The L5P lift pump, by design, maintains 58p-62psig in normal mode and 75psig in active DPF regeneration mode, to keep the HP4 and the 9^th injector in proper pressurised condition and status. By design, the system only supplies the fuel required to keep the correct pressure in check and varies its pump speed on demand as load and return flow by the injectors increase. By design air induction into the system is minimised by this, and therefore needs not be mitigated. Furthermore, with the revamped design and internal port matching of our fuel filter head the system experiences less overall backpressure which puts less stress on the lift pump at higher horsepower levels.

Diesel Gelling concerns??After reading the above, and understanding the theory of operation of the L5P lift pump, it is easy to see why gelling is mitigated by the system. Since the lift pumps sends fuel through the fuel filters that equal consumption rate, + injector return, + HP4 injection pump return, the fuel heater that sits inside the filter head has a chance to increase fuel temperature above the gelling point. This is contrary to aftermarket lift pump designs that send flow through the system INDEPENDENT of fuel demand which increases the cooling effect of diesel fuel and do in fact cause gelling. This has been seen in the industry for years, and the L5P lift pump and fuel pump driver module take care of this by increasing flow based on demand not independent of it.

Water in fuel detection??The water in fuel conductivity probe that sits down in the fuel filter head, in the water/fuel filter, works to detect water intrusion and emulsification in diesel fuel. The fuel pump driver module sends a 5 volt signal to the conductivity probe and as water % increases in the fuel system the probe will start to flow electrons from one end of the probe to the other. Since diesel fuel isn’t conductive and water is, the probe, and therefore the fuel pump module will begin to detect voltage. As voltage increases through the 3.5 V range the water in fuel light and a check engine light will illuminate to alert the driver that the system has detected the presence of water in the fuel system. It is critical that the probe (similar to OEM) be positioned as close to the lowest point of the fuel volume in the filter as possible so the probe has a chance to pick up the water column in the filter. If the filter is replaced with a filter that is 3 or 4” longer than the factory sensor range then there could be a lot of water in the fuel system prior to the probe picking it up and reporting it back to the ECM for the algorithm to take action on ---  oooofffff

Advantages:

• Direct bolt on in under 30 min time.
• Water/fuel filter pre filters down to 13 micron with the usage of our readily available Donaldson Part number 551329
• Post filter down to 3 micron with the usage of our readily available Donaldson Part number 551313
• Maximizes usage the factory L5P fuel system fuel heater to prevent gelling in the winter
• Maximizes usage of the factory L5P water in fuel sensor to alert owner of water in fuel accurately per the owner’s manual.
• Combined water filter and fuel filter cost less than the factory fuel filter
• 18% more surface area for water / fuel filtration and 100% more surface area at a higher filtration efficiency during post filtration
• Supports higher horsepower levels due to full internal patented port matching of the filter block and lower differential pressure across the fuel filters than compared to the factory (1000 RWHP compatible)
• Lifetime warranty for fit and finish
• Quicker fuel filter changes and longer interval change times. (15,000 miles +)
• No requirement to change calibration or block P codes to gain increased fuel filtration as some lift pumps require.
• Allows cleaning of diesel fuel while maintaining proper pressure requirements to the inlet of the HP4 injection pump