Something you should know about your diesel truck, specifically the CP4 Injection pump and the potential catastrophic damage that may be happening or already happened.

If you’ve been down this road before, don’t be left with a $10,000+ bill from the damage it causes: leaving metal shavings in the fuel rails, destroying injectors, and returning to the tank contaminating the entire system that needs to be replaced, and in some cases cracking the gear and throwing it through the front timing cover of your engine.

Everyone with a diesel knows the potential that they have with simple tuning and deletes. Previously on older models, there wasn’t much of an issue with the fuel system, but with the newer models there was a design change introduced as a cost reduction to the LML platform, (since a smaller amount of fuel is required when running the more efficient piezoelectric injectors). Even if you have a 100% stock truck your pump is still a ticking time bomb.

The new CP4 injection pump creates higher pressures with less volume meaning a more efficient pump, but with the lack of volume is a lack of lubrication, therefore creating these failures. In Europe the CP4 has been used for years with very little trouble, reason being is their fuel has more lubricity than our country's Ultra low sulfur diesel fuel (ULSD), and does not even come close to meeting the minimum spec for lubrication to keep highly stressed components like those hydraulic pistons in the pump lubricated.

You accelerate wear any time you fill up with ULSD. There is an assortment of additives on the market that aid in lubricating our poor quality fuel we have to use, and while it does help; it does not solve the problem with the CP4s lack of fuel in modern diesels, which creates more power than these pumps can handle, without some help from the aftermarket.

With the aftermarket there are finally ways to prevent these failures. The most popular for the Duramax platform, is to convert back to the proven CP3 used in 01-10 Duramax and 03 and up Cummins. (There is a reason Cummins still uses the CP3 - if that doesn’t tell you something about its durability). These kits are complete and come with everything you need to do the conversion on the 2011+ LML. This is also the most cost effective way to prevent a CP4 failure in a Duramax. Other companies offer a dual fueler kit to add a CP3 in conjunction with CP4 pump providing enough fuel for 1000hp or more. This is popular in the 6.7 Powerstroke application, that doesn’t offer a CP3 conversion kit. While it still keeps the CP4, it does take the stress off the pump meaning less wear for a truck that’s demanding more fuel.

Another important part of the fuel system is the filtration. With aftermarket lift pumps (Duramax's do not have lift pumps, just injection pumps), from companies like Fass or Airdog, they have built in fuel filters and water separators, so you can rest assured you are providing positive clean fuel pressure to your injection pump, (keeping the pump from having to pull a vacuum from the fuel tank, which will greatly reduce the stress on the injection pump). A lift pump is something we highly recommend on any diesel that comes through the shop tuned or not. A lift pump will help extend the life of your truck, and the extra filtration will pull out the contaminates and water in the fuel.

Now you may be wondering what the cost of these solutions for the CP4 injection pump are. There are several companies that offer conversion kits for LML’s with a new CP3 pump provided, or without ranging from $600-$1800. With options of modified CP3 pumps, some kits are in the $2500-$3000 range. Not all kits require the truck to be tuned or deleted and can be used on a 100% stock, emissions legal truck with no tuning required. The ECM does not care about the volume of fuel, it just wants to know the fuel rail pressure and regulates the pump by the FCA (fuel control actuator), to increase or decrease pressure. The dual fueler option is $2000-$3000 depending on if you choose a kit with or without a pump, and whether or not you want a modified CP3 or a stock one.

Lift pumps come in specific kits to fit your application and typically are a fairly straight forward install if you’re a DIY’er, kits range from $600-800 for most applications. All of these parts will be listed in time on my website for purchase and delivery. In the meantime call the shop or come in for any orders. We offer full installation of all the parts talked about and much more for your diesel truck.

Check out this website for all contact info and directions to the shop. Also visit our Facebook pages Race Ready Fabrication, LLC and One Stop Diesel Shop to keep up with any future updates.

Corey Sadler

Owner and Operator

Shop- 603-734-4775


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