Why do CP4 Injection Pumps fail and take everything with it?

In model year 2011, both GM & Ford got a revamp on their fuel systems. While these are two different vehicle manufacturers, both their Duramax & Powerstroke power plants share the same diesel injection pump, the Bosch CP4.2.

GM used the CP4.2 in the LML Duramax, (MY 2011-2016)

Ford uses the CP4.2 in their 2011- current Powerstrokes, with a lift pump, however.

This move to the CP4.2 was in part by its ability to provide higher injection pressures for better fuel atomization resulting in cleaner emissions. This was not without downfall as problems began to occur. Truck owners & enthusiast began having these injection pumps fail and they quickly realized that when it fails, every part of the fuel system has to be replaced. Fuel Lines, fuel rails, Injectors, and everything associated, the fuel tank also needed dropped and cleaned.

Why is it necessary to replace the entire fuel system after a failure? One must understand how fuel flows in the CP4.2 first. We have done our best to put together a visualization of how the fuel flows through the CP4.2.

Shown below, visualize the Orange Wire is the fuel.

The fuel comes in the inlet fitting, to the cam driven pump that is bolted to the back of the housing. This is what pulls fuel in from the tank and brings it into the injection pump.

From the Cam Driven pump, fuel then routes into the case body to lubricate the cam & rollers.

Fuel from the case, then routes up to the MPROP/FCA, which is what is commonly pulled to confirm a failure.

The fuel routes through the screens of the MPROP/FCA, then down and through the center of the MPROP/FCA, which leads over to the plungers.

The fuel routes into the plungers, which is then pressurized by the roller & cam pushing the plunger and spring and fuel then is sent at 30k+ PSI to the fuel rails.

Where is the failure point you ask? The failure resides in the pump body, where the rollers ride on the cam lobes, shown here

In the event of poor fuel, lack of lubrication, etc. It is possible for these rollers to wear down and create metal shavings. These metal shavings are a lot finer than the screen on the MPROP/FCA, which we saw was the next step in the flow of fuel after the case. When this metal gets past the MPROP/FCA, it contaminates the injectors, which then contaminate the injector return line, the rails, and all the sensors.

Below, you can actually see the failure of this pump, one of the rollers started grinding away, and sent metal through the system. As you can see on the calipers, this roller is out of round as it has been ground away by the cam.

How can this costly repair be mitigated?

On the LML Duramax, you can CP3 Swap, which a less failure prone injection pump, and was the pump of choice in the 01-10 model Duramax.

You can read more on the CP3 Swaps here!

On the 2011+ Powerstrokes, a CP3 Swap isn't an option unfortunately as the CP3 is just too large of a shape to fit where it needs to.

The go to for these trucks, is the S&S Diesel Motorsport Gen2.1 CP4.2 Bypass kit! Which you can read more about here!

We carry both options for these trucks to best suit our customers needs.

I hope you've learned something from this informative blog!

Thanks for reading.