HERE'S WHY CP3 REGULATORS FAIL

If you own a common rail diesel truck, be the Cummins Duramax Power Stroke engine and have boost and idle so you can hear the engine speed oscillate a little or maybe light crews 55 miles per hour 60 miles per hour light load w

here

you can feel the engine shake a little, it just can't keep it running nice and smooth, a lot of times that problem can be traced back to the fuel pressure regulator and the problem the truck is having is that it can't control the fuel pressure. and as a result you get varying amounts of fuel volume, the torque is changing and as a result the engine speed changes.

Today we're going to delve into how the fuel pressure regulator works, look at its little parts, see what goes wrong, see how it may or may not be fixed because it's a sealed unit, but it's really interesting to see how it works. I'm going to show you, so first things first. I've got a bunch of dead CP3s lying around, so we took the

regulators

off them. and I opened them up so we can see what's inside this thing and how it works, because the first part of knowing how something

fail

ed is knowing how it's supposed to work properly, okay, forgive me if I don't name all these parts correctly, but you.

To see the image, we have this end

here

that is pressed against the casing. The housing is basically a solenoid, so if you look inside the housing you will see an opening at the end that is a two wire plug. That plug only has two wires. Okay, inside that casing there's a coiled cable and inside of it falls this pivot piece, I'm not sure if that's the exact name, but to me it looks like a pencil and basically when that coil activates it forces this pivot to come out, a good way to test and see if a regulator is even remotely good is to put 12 volts on it briefly, not for long, and see if it clicks, if it clicks, that's fine, it means the pivot system is moving , the slide is moving, the regulator can regulate the fuel if I take this.

New regulator that I think is bad, I connect wires to it, put power to it and I don't hear it click, that's a sure sign that the slide is not moving, the pivot is not moving, so for some reason that pivot is stuck in the hole and the slide mechanism can't work which means it won't control the fuel which means the regulator will most likely be stuck at maximum rail pressure all the time. You will know because the truck will output p0088. and it will run extremely rough and sound like it wants to fall apart, let's see how the regulator control system works.

I showed you the inside of the case, the pivot, then we have this front half that I cut out for convenient viewing, it fits like this, the pivot. acts on this, this sliding piece, the sliding piece is inside the end of the housing, now we have fuel pressure that wants to enter this hole right here, so when the fuel pressure comes in, it will be re, its flow of The output will be regulated to these four holes on the outside of the regulator, so in the event that we apply fuel pressure to this hole and there is no current, which means that the system is completely open, we would have a full flow of fuel to the cp3 pump, which means that the pump can generate the maximum pressure or move the largest possible volume of fuel, the largest mass of fuel if we put 12 volts on it, which is idle or closed, so that is the highest fuel pressure low, the lowest fuel flow we can run, so it's kind of a backwards system in that way that you need. power to run less fuel i cut this slide because it's interesting to see how the fuel gets to the end here it goes inside the slide which is held in place by a spring and then the position of this slide really dictates how much fuel is allowed to flow through those four holes now the really cool thing about this slide is that they changed it from different years and tuners or people who are familiar with modifying these trucks will notice that the fuel pressure regulator amperage or current required for different fuel flows changes As you go from an lb7 to an lbz, if you look at the shape of the slide on this lb7 you can see that it has a very narrow hole which then drops down to a very large or rectangle or block shaped hole when you go to the lbz It has a very different shape, it basically looks like an arrow pointing to the left, that arrow pointing to the left is those four arrows that point to the left and dictate the shape of the fuel pressure regulator stream, so that when you put an lbz regulator on an lb7 it's important that you change the current fuel pressure regulator table to reflect the shapes and this slide, let's see how the slide moves because okay, so if you look at my nail on my index finger , that would be the end of the regulator facing up. against that end would be the spring and then the spring would force the slide back when I apply 12 volts, that slide will be its lowest hole so the least amount of fuel will flow and you can see my nails all the way. to the right as I release my finger, which has no spring, but I'm basically using it as a spring that forces the entire slide to the left and as it moves to the left, you get more orifice flow and that orifice flow allows the fuel goes in through the end of the regulator and out through these four holes around the outside, okay Nick now I know how the regulator works, it's not rocket science, why is my truck climbing fine?

So the interesting thing that happens over the life of your truck is that there are many fuel pressure adjustments, the load changes frequently on your truck every time the rpm changes every time you step on the accelerator every time those two things happen at the same time the position of this pivot moves and will move a lot at low load because you are usually operating your truck at low load so what happens is this pivot wears out over time and if you look closely at the bottom of the pivot You will see wear marks on these parts, the more they wear the more they don't move well and when things don't move well you don't get good granular control why do I say granular? why not control well?

You need the most granular control, the most complex motion control at very low loads because remember the difference between 10 horsepower and 13 horsepower is so different that the difference is much larger than the difference between 130 horsepower. and 140 horsepower if your truck makes 150 horsepower and the fuel pressure goes up a little bit and you make 145 or 150, that's not that big of a deal, you probably won't feel it; However, if you're asking for 15 horsepower and your truck jumps to 25 horsepower, that's a problem, you'll feel like there will be an increase and if so. continuously because remember the system is on a pid control which means it is constantly analyzing the actual fuel pressure compared to the desired one and adjusting this, that pid control only works when you have smooth movement so if you exceed too much in one direction, it usually overshoots to the other side if the system is out of calibration, and it's going to be out of calibration if you have sticky parts, how else can this happen? you get bad fuel, you park the truck for two years and don't drive it and the fuel degrades in the regulator, all of these things we've seen have led to poor regulator performance in one aspect or another.

Now many times the regulator gets stuck in the full on position and that, in that case, when the truck is started for the first time. You will immediately notice that the fuel pressure is too high, you will feel it running extremely hard, the truck will feel like it is working too hard, a lot of rattling, a lot of engine noise, that is excessively high pressure in the rail and that is just the pump is stuck at full tilt and should say full tilt all the way to the left, in that case the regulator is faulty of course now you can sometimes prevent the rise by putting two stroke oil in the fuel transmission fluid in the fuel is kind of a lubricity enhancer and what that's going to do is free up the regulator pivot in its hole a little bit, allow the slide to move a little more freely, as long as that slide can move freely, we have good control of the fuel and we can mitigate that increase, ultimately what will happen is that the regulator will degrade to a point where it will lose control completely and you will have to replace it.

Now there is one last scenario where you might encounter a surge and that is when you first install a low voltage. pressure boost pump as a supplemental pump, call it quick titanium 165 which is what we sell or anything on the low side of the system that will increase fuel flow on the low side of the system and add fuel pressure. Occasionally we see guys put a pump on the low side of the system that is too big for the high side of the system or has too high a pressure, so on a lb7 for example there is 8 to 12 psi is the pressure desired low if you put a pump on that side on the low side of the system that gives you 25 pounds of pressure, when that pivot moves the slide against the spring all the way to the right, you can't hold it there and what happens is the spring combination and the tall The fuel pressure pushes the slide open and you lose control of the rail pressure and what you will see is the rail pressure will increase from what you want, which could be five thousand psi up to eight thousand ten thousand twelve thousand psi, it could keep going up, you can see it especially when you are off throttle or the engine speed is a little higher and the fuel demand is extremely low, in that situation you will want to check the low side fuel rail pressure, make sure it is within spec again, 8 to 12 psi at lb7. lb 20 psi on a Cummins or consult whoever you bought the pump from and get the recommended fuel pressure to summarize, as long as you have a good low side pressure and a good performing regulator you should be able to get away from that surge at low load. and idle if you're watching this video and you think I have this problem I'm going to call these guys and see if I can get them to help me I'm going to stop you right there and tell you we're probably just going to sell you a regulator and tell you to put it in the truck or we will tell you to check the low side pressure.

If you found this video helpful, please click the subscribe button. It's hot. I worked hard to get them all. Besides, give me something, man, help me, I'm pregnant, Nick, this is diesel, ideas that we'll see next time.