I know there are some posts in here about some similar problems, I'm not sure if it's the same thing or not. I have a 2003 Dodge 2500 with the Cummins 5.9L turbo diesel. It's been doin this thing for a few weeks now; It will (USUALLY) run ok in the morning to work, and then again back home in the afternoon, bout an hour drive. If I go anywhere after that though, (while the engine is still hot) when I stop at a light and it's idling, the rpm will drop, then come back up. Just occasionally sometimes, but alot other times, and sometimes the engine will just stop. Usually starts right back up. Gave me alot of trouble yesterday evening, and today on the way home the engine stopped twice at a light and it took a few seconds to start back up and it gave me trouble the rest of the way home. I can't find where it could be sucking air, I've checked the clamps. I have changed both fuel filters (it has a secondary). It does it with the fuel at varying levels, so I guess I could rule out a crack in the pick up tube in the tank. I have put fuel at different locations and it still does it. It went 5 days running ok after the main filter change and draining the filter housing, then it started again. I read in a few posts something about the fuel control actuator. Guys, as my handle says, I'm a newb to diesel engines and I'm pretty much broke so I can't throw alot of money away letting a shop play with it for a week or so. Any and all help is appreciated.

 

Can you check what your fuel pressure is? The pump could be going.

 

As SAVOY stated, your pump (lift pump) might be the culprit. Could also be the FCA (fuel control actuator) on the backside of the CP3 giving you issues too. Does the idle ever become erratic, racing up on it's own without any throttle input? If so, then I would lean more towards the FCA being the problem.

 

Idle isn't erratic really, it'll drop and then when it tries to compensate it will go higher than normal idle but then right back down to normal idle. But it happens alot lately.
CP3...I don't remember what that is.

 

CP3 is the high pressure pump feeding the fuel rail. Do you have an automatic? If so it could be the torque converter is shot. Other than that I'd lean more towards the FCA as the culprit.

When my FCA went south the engine would race up and down on it's own.......at any given time.......might be 2-3 times a day......maybe once a month.....it was very random when it would happen. RPM's would go (always happened while at idle) from idle to almost 2000 and back down and then happen all over again.

 

It is an automatic, but the transmission shifts fine.
The rpm doesn't race, or go up, it drops. At random times. Mostly at idle. It will be idling and the rpm will just dropto aboult half for a second, then come back up to idle. Or it will drop so much that the engine stops. It used to only happen only after I got hoe from work and then drove it again.Now it's happening alot, nearly allt he time and it's getting harder to start when it does.

 

I'm thinking FCA.

 

Well I drove it Saturday into town and it ran fine. I don't get it. Water in the fuel/bad fuel?

 

FCA will act up very intermitently. You may want to have someone hook up a scanner and watch what your actual pressures are.....mine would go anywhere from idle (5k psi) down to 3k psi and ramp up to 9k psi.....at any given time.

 

Im thinking FCA also. Get one from Cummins. about 100$. easy to replace, just get correct bit for torx screws, whack with a hammer to shock them loose. way easier to replace then.