LBZ CP3 problems [Archive] - Duramax Diesels Forum


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11-21-2010, 03:39 PM
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.

11-21-2010, 03:45 PM
So are the lbz cp3's not made as well as in inside parts that make them fail with some miles on them?

11-21-2010, 03:47 PM
They have a ceramic check ball that can fracture and cause it to not be able to hold rail pressure as well. I'm not sure what else is different, but John at Floor It and Shane at Wicked Diesel both have had bad things to say about them. Makes me wonder since they are both really smart guys when it comes to these pumps.

11-21-2010, 03:51 PM
Interesting... thanks for the info.

11-21-2010, 04:06 PM
Heard the same thing Josh:(

This year i had a lb7 cp3 explode and the lbz was cheapr to buy than the i made the plunge.

Both have ( to me ) worked great. but as you know Abby get very few miles on it.

11-21-2010, 04:09 PM
mine actually went out at 45,000 ,dealer replaced it for free, but at the time i talked to shane and he gave me the same info.:confused:

11-21-2010, 04:11 PM
Where are the ceramic balls?

11-21-2010, 04:37 PM
above the pistons is where i understand it , was sitting in a chic-fila drive thru when mine went out , check engine light came on and was still runnin but no power. i think the only thing keeping my truck running was the lift pump:)

11-21-2010, 04:38 PM

11-21-2010, 04:45 PM
That could cause injector problems too from the metal shavings running through the fuel rails too. Keep that in mind also..

11-21-2010, 04:50 PM
So if you have a lbz cp3 when and with what(model) should you replacce it with?

11-21-2010, 05:11 PM
yeah they replaced all rails and injectors

11-21-2010, 05:14 PM
That could cause injector problems too from the metal shavings running through the fuel rails too. Keep that in mind also..

What r u talking about??:confused:

11-21-2010, 05:22 PM
If you read the TSB, you would know... The metal shavings from the ball run through the rails and could take out the injectors too

11-21-2010, 05:29 PM
Here is the TSB report

11-21-2010, 05:38 PM
Awesome tech Josh! I'll b stickin with my lly cp3 to work on

11-21-2010, 06:17 PM
Here is the TSB report Henry. It was 3 MPa fluctuation, not 3000 psi. I'll edit my post.

I'm not sure if the pumps I replaced had a fractured ball or if they were just worn out, but neither had any debris in the rails and no cups were blown out.

09-22-2017, 08:14 PM
Many years later, we just replaced another one. Completely stock at 140k miles, not even a tune.