2001 duramax w 185000 miles. Runs around town great. But when I get out on the highway it will run good to about 70. than pulling a hill it will kick the motor into limp and only run about 1800 rpm. if I ask it for more, it will jjust down shift. Put a new fpr cp3 and shimmed the fprv. It has a rapter boost pump. It did this before the pump as well. Chevy dealer said it was the cp3 but that didn't fix the problem.. NEED HELP... ......

 

is there any codes? if it is going into limp mode then there should be at least one code. this will help a lot as there could be many reasons for a limp

how old is the fuel filter?

 

Ya it threw a code. It was saying that the fuel rail pressure was high. That it had a open circuit . The computer that it was hooked to was a older so not sure what the numbers were. The fuel filter was changed about 2 weeks ago. Only has 300 miles on it. I wanna say the code was 1309 but not positive on that.

 

It threw a p0093 code. Changed out fuel lines and filter. Someone told me the lb7 is famous for the o rings on the injecters to go bad. I'm so tired of putting money in this thing. Any ideas. No fuel in the oil no smoke white or black

 

it is actually the check valve in the injector that is the LB7s problem.

injector problems typically manifest themselves at lower rpms like idling and driving around town and not on the highway.

i would look for cracked, old, deteriorating fuel lines and replace any suspicious ones. you can replace the one coming out of the filter housing with a clear one to watch for bubbles in the fuel.

does the primmer bulb pump up hard? if not try pinching the output line and see if it pumps up hard. if not then you have a problem with air getting in the fuel around the filter housing. if it does then the problem is further down the line.

if all of the lines are good and no air is getting in the lines then it may be one or more injectors

 

Ya I pumped it just to see the other day after I had changed a few of the fuel lines and it was pretty hard. The line going in and the one going out of the filter housing I changed and they are really hard to ( the hoses) .so I am going to change out some more lines. I think I'll need all the help I can get on this one. If its a injected on one side of the engine can you just replace the 4 on that side or is it better to just do them all

 

yes, you can replace the injectors on one bank. many will replace all 8 as it doesn't take much more to get into the other side

the LB7 has one line on each side of the cylinder banks that the return fuel flows out. you can test the amount of fuel coming out and see what bank has the bad injector(s)

 

On the check valve on the injecter if its not working will the fuel go back in the return line or in the oil. I'mnot loosing my prime or anything so if it was a leek wwouldn't I lose my prime.that is why I'm thinking either a kink or a injected or multipul injecters

 

the fuel will drain out into the return line if the check valve is bad.

loose return line bolts or bad seals on the return line bolts under the valve covers will leak fuel into the oil. also the previously common issue of cracked injector bodies will cause fuel to leak into the oil.

any problems after the CP3 pump will not likely result in loosing prime. it would take considerable pressure to be able to push fuel through the CP3 without it running. the hand priming bulb is not likely able to make this much pressure. if you are holding prime then you don't have any leaks on the lines after the filter housing up to the CP3. kinks and collapsed lines are still a possibility. also leaks before the filter can let air in but not affect the ability to pump up the bulb hard. this is why i like the clear line to watch for any bubbles.

do you have any scanners to see what the fuel pressure is?

 

I'm going to a shop Friday that has a good snap on scanner to see about pressures and whatever else he can help me with. I'll put the clear hose on as well and check that. Thanks for the help. Hopefully we can get her fixed. Been a great truck.