Bad CP3 or what?
 

Hi,
I'm trying to figure out what is going on with my 2003 5.9l cummins with 196k on it, and has airdog fuel system, smarty tuner. Truck was very difficult to start when it gets cold out, after reading and talking I replaced the injectors, grid heater solenoids, batteries, fuel filters, FCA and problem is still there and has gotten worse. The truck previously before any repairs wouldn't start under 40 degrees, now I'm lucky to get the truck to start when the temp is less than 60 outside. Also if I go to drive the truck, when I get to a stop light and idle then once the light turns green and I start to go whether I barely give it fuel or hammer on it, the engine bogs down and Rpms drop around 300-500 and then the truck takes off like it's fine with little smoke. On top of that the truck will randomly just completely stall/die on the road once in awhile but every single time it fires right up and I can continue going like it never happened? I had fuel pressures tested, at idle it idles fine and according to readings they fluctuate somewhere between 3600-7000 psi. When I drive it and stop and start to go the psi drops to around 900psi then catches right back up to desired pressure. I'm completely lost on this and my head hurts from trying to figure it out and any help would be greatly appreciated!

Have you done a throttle position sensor yet? Is there a CEL?

Have not looked at the throttle position sensor, and no codes at all

I would cycle the key 3 times to see if there is a soft code stored- if not then I wouldn't mess with it. Sometimes it will store a code and not throw light for some reason

No soft codes listed

Pull your regulator Off back of cp3 to see if any junk in there. May be sticking up

No crap stuck in there or on it. When truck was hooked up to computer and FCA was tested it was responding and working like it's supposed too. At idle you could push the pedal all you wanted and it would respond correctly but that's with it in park. Starting when cold and driving are the main issues right now. There's really only 3 possible causes left: CP3, PRV, or fuel pressure sensor and since the truck runs fine at high rpm I doubt it's the PRV

I had a friend and the pressure release valve completely crapped out once we plugged it was fine. take the banjo bolt off and if its bad you'll know because itll look like a damn garden hose. we plugged his and so far no problems the PRV shouldn't actually open until 26kpsi I think and a stock pump should never reach that at an idle.

I'll try it tomorrow along with the new fuel pressure sensor as long as it comes in the mail like it's supposed too.

Well I finally got some good news, the injection pump was the problem, industrial injection said it was damaged internally and had to get it rebuilt by another company. Finally got new pump installed and truck actually started up but idles absolutely horrible and white smoke pours out the exhaust and has a knock, not sure how this is possible at all.