Ok, have a friend who has a 05 cummins with 165k.. Was running good then started acting up. lots of blue/white smoke. barely idle chuggin pretty good. He put new injectors in. #4 and 5 were hung open when he took it apart. Replaced with DDP 50hp complete injector. fired it up still the same thing, little better... Not hardly any white smoke. Seems to run ok at 2k rpms, but if you mash it it fallls on it's face untill it cleans out. He said he got some bad fuel that he thought killed the injectors. I put a fuel pressure guage before the cp3 and he was only getting about 8psi at idle.. The guage seemed to dance around with the stumbling of the motor. No codes or lights either.New fuel filter. Any help or thoughts would be appreciated. I would like to see rail pressure, but I don't have a guage for that. Also, doesn't 8psi into the pump seem low. Thanks

 

I'd start by checking the lift pump.

The CP3 can pull enough fuel to make the truck run, but it won't run very well like that...

 

Well, when we cycled the key the fuel pressure went to 7psi right away.. So that tells me the lift pump is working..Right... I think it is on the other end coming out of the cp3. But I don't have a Rail pressure guage. I think I need to invest in one for the shop.. I usally mess with 12v's. No rail pressure Needed!!

 

If you verified proper lp operation, my next step would be to check the pressure relief valve.

There is some good info in THIS thread on how to check that.

If that all checks out, I fear he may have more injector problems...

 

Did you install new connectors tubes with the new injectors?

 

Any update on this?

 

Did you check wires to injectors. I had to change a few of these valve cover gastkets since the harness had too much resistance. Was causing injectors to cut out.

 

So, Is all the white/blue smoke gone at idle?