Guys I have a GMC Sierra 2500 HD with the LB7 Duramax. Truck is bone stock, with 175K on it. I actually got a screaming deal in this truck due to it having an issue that no one had been able to figure out.

When I got it, periodically upon start the truck would idle rough and throw codes, and even go into limp mode. The code indicated low voltage on the circuit that had the throttle encoder, and a couple of other sensors. As it turned out, replacing the Fuel Pressure Regualtor fixed all the issues, except that I feel like this truck just does not have the power it should.

I am using a Diablo Sport programer and think I have diagnosed my problem as my CP3 pump is just weak. With the Blue Diablo connected on level ground (low PWR demand) the Fuel PSI Actual follows the Fuel PSI Desired very closley. When I push the pedal down my desired FP increases as high as 150KPa but my CP3 will only put out 62KPa. When I let out of the pedal the FP desired drops and the actual will move up some past 62KPa, which I assume, is due to the reduced need for fuel, and once again the PSI Actual follows the PSI Desired.

I changed my fuel filter this weekend and did notice some increase in power, which makes me think the CP3 pump just will not make the pressure needed to build power.

 

i think your headed in the right direction but...i would check the tank first for junk rule that out if all clean then i would do the cp3...scott