CP4 Fuel System Failure
CP4 Failure on 6.7L PowerStroke, 6.6L Duramax, & Dodge/Ram Cummins 6.7
Be sure to check out our article on DEF in your fuel system as well as Will my Insurance Cover my Fuel System Failure?
P0087 (Fuel Rail Pressure Low)- This is a hard one to swallow, but a simple one to understand and diagnose.
Things to Check:
First thing to check is that you have more than ¼ tank of fuel. We’ve had a couple of instances where customers believed to have more fuel than they did and it will throw this code simply because your truck doesn’t have enough fuel to supply to the pump. You can also experience this code after changing fuel filters and incorrectly priming the fuel system. We typically recommend at least 5 Key-on no starts of 25 seconds after changing your fuel filters before attempting to start your truck (this excludes LML Duramax, you’ll need to pump the plunger until it gets firm and bleed at the Schrader valve). This ensures that as much air possible is out of your fuel system, preventing CP4 wear.
Ensure that you don’t have any visible fuel leaks. Take a look underneath the truck and make sure you don’t see any fuel on the ground, around injector lines, in the valley (tough to see), near fuel filter connections (under truck and under the hood).
Ensure that no rats or varmints have been living under your hood. We’ve only seen this once, but a rat did actually chew through a wire from the fuel rail pressure sensor. Make sure if you’re fixing this wire that you solder it back together, this ensures accurate voltage to or from the PCM
Time to find a data-reading capable OBD test tool
Most mechanics shops will already have this tool, but if you’re the do it yourself type then most auto parts stores will carry this type of device. It’s going to come with a bit of a price tag but it’s always something useful to own! We’re looking for 2 data point here under engine/fuel data: Fuel Rail Pressure Desired (FRPD) & Fuel Rail Pressure Actual (FRPA). Typically what we see here is that our desired pressure is somewhere around 4-5,000PSI (this is pretty standard and you don’t really need to monitor this one, all this is data point is showing you is that your truck needs this amount of fuel rail pressure to start). Our actual fuel rail pressure is the data point to watch, start by cranking the truck and watch this number, if Actual Pressure is somewhere around 350-500psi this the first sign you have a high pressure CP4 Fuel Pump Failure.
Conclusion on Things to Check: Just because you are showing low fuel fail pressure doesn’t always mean that you have a faulty pump. Some instances of relief valves and VCV (volume control valve, which sits on top of the pump) can be known to cause this issue. Unfortunately, we see more instances of bad CP4 pumps than we do with bad sensors.
The only real way to completely fix this problem isn’t a cheap one. If you think that you have a bad CP4 pump (best way to check is to remove the VCV on top of the CP4 pump and see if there are metal shaving) the only way to resolve the problem is by completely replacing the fuel system in the vehicle. Replacing your complete fuel system includes: Injectors, lines, rails, sensors, CP4 pump, fuel filters, dropping your tank to drain and clean it, removing the hard lines from the tank to the secondary fuel filter and cleaning them, cleaning or replacing your low side fuel filter housing and a couple other items.
Why did this happen:
A couple of things to note here, the first being change your fuel filters on a regular basis!! The primary cause of high pressure fuel pump failure is lack of lubrication. The CP4 pump is lubricated by diesel fuel, if you don’t have a constant supply of good, clean, fuel to your pump you’re causing damage every day that you drive it. Another cause is water or contaminants in your fuel, again this goes back to changing your fuel filters and keeping up with regular maintenance. Lastly, DEF in your diesel truck will cause this issue, if you’ve accidentally poured DEF into your diesel tank, DO NOT START THE TRUCK. So long as you don’t start the truck, or immediately turn if off after you notice it, this problem can be fixed without replacing your fuel system. Water is more dense than diesel so the DEF fluid immediately travels to the bottom of your tank which is where your low side fuel pump extracts fluid from. In all cases where the truck hasn’t run after having DEF in the fuel tank, everything can be salvaged (clean the tank, replace the sending unit, replace any rubber lines the DEF flowed through, ETC.). If DEF makes it into your high pressure fuel system, at some point it will begin to crystalize and clog injectors and lines and destroy your system.
What can I Do to Prevent CP4 Failure?
A couple of things to note here, as I said before change your fuel filters every 10-15,000 miles with OEM (Ford, Chevy, Dodge) Brand Filters. Install an EPA Compliant CP4 Disaster Kit (Highly recommend the one from S&S Diesel for Ford Applications). This will save your injectors, lines & rails from contamination. Should you have a pump failure it will send most of the metal shavings back to your tank and through your fuel filters to be picked back up. In most cases we don’t end up having any injector issues when this kit is installed. If you own a Chevrolet 6.6L Duramax 2011-2016 we recommend installing a FASS fuel system as these trucks do not come with a factory lift pump to supply fuel to the CP4 Pump.