As some of you know, I work part time at a local diesel shop. In the past month, we've had 2 trucks (1 LBZ with 225k miles, 1 LMM with 204k miles) come in with rail pressure problems.
The first truck came in about a month ago. We hook up the fuel pressure gauge to the test port to look for restrictions in the fuel system, but both times they show to be ok. If you log the rail pressure, it holds ok at lower RPMs, but once the RPM gets up above about 2500 it starts to drop pretty quick down to about 22,000. Keep in mind this is on completely stock trucks. Since we don't have a way to test return rates on injectors (I've been trying to talk to my boss about getting some parts together to make a kit), we thought it was just lots of miles on the injectors and they needed to be replaced. I remembered the TSB about the ceramic ball causing rail pressure problems. It said to command rail pressure to 23,000 or something like that and it shouldn't fluctuate more than 3 MPa or the CP3 was bad. I did the test, and it showed ok. We put 8 new injectors in, and the rail pressures were doing the exact same thing. So that only leaves the CP3. My boss called John at Floor It diesel, and he recommended we use an LLY CP3 with steel check balls and an LBZ regulator. We get one from him and put it in. Problem fixed.
Then a couple of weeks ago, the LMM comes in showing the exact same symptoms as the LBZ. I feel pretty confident it is the same issue. We get another CP3 and put it in. Again, problem fixed.
I seem to remember Shane at Wicked Diesel also saying something about not liking the LBZ pumps either. I kind of wonder if we will see a lot more CP3s failing as these trucks get more miles on them.
The first truck came in about a month ago. We hook up the fuel pressure gauge to the test port to look for restrictions in the fuel system, but both times they show to be ok. If you log the rail pressure, it holds ok at lower RPMs, but once the RPM gets up above about 2500 it starts to drop pretty quick down to about 22,000. Keep in mind this is on completely stock trucks. Since we don't have a way to test return rates on injectors (I've been trying to talk to my boss about getting some parts together to make a kit), we thought it was just lots of miles on the injectors and they needed to be replaced. I remembered the TSB about the ceramic ball causing rail pressure problems. It said to command rail pressure to 23,000 or something like that and it shouldn't fluctuate more than 3 MPa or the CP3 was bad. I did the test, and it showed ok. We put 8 new injectors in, and the rail pressures were doing the exact same thing. So that only leaves the CP3. My boss called John at Floor It diesel, and he recommended we use an LLY CP3 with steel check balls and an LBZ regulator. We get one from him and put it in. Problem fixed.
Then a couple of weeks ago, the LMM comes in showing the exact same symptoms as the LBZ. I feel pretty confident it is the same issue. We get another CP3 and put it in. Again, problem fixed.
I seem to remember Shane at Wicked Diesel also saying something about not liking the LBZ pumps either. I kind of wonder if we will see a lot more CP3s failing as these trucks get more miles on them.
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