5.9 Cummins Stumble

[Dave_Pete]

Have been experiencing an assumed fuel problem.

2006 Dodge Ram 5.9L Cummins turbo diesel. No check engine lights.

Increasing, and intermittent (becoming MUCH less intermittent) stumble and rough running under LIGHT acceleration. When the problem occurs, it almost feels like it doesn't accelerate as well under heavy demand either, but that is hard to tell - stills runs quite well at higher demand and is pulling an 8000+ lb trailer up hills quite well (I'm away from home base). The stumble seems more to be during light throttle and between 1100-1800 RPM and at speeds up to 50. At cruise (1600 RPM) a slight stumble, but not really bad at all.

Also had a few episodes of white smoke and rough cold-start idle a while back. Since then I've been using "Howes Lubricator - Diesel Treat" because at THAT fuel stop it was the one on the shelf that was for fuel injector cleaning as well as diesel conditioning and anti-gel. After a very short time, no more episodes of rough cold idle or evidence of white smoke. But still - the other light acceleration issue.

I discovered a light oily condition around the fuel filter housing screw-off lid and backside hoses, so checked the lid tightness. Yep - I failed to tighten it more than hand-tight at the last filter change! The stumble had never occurred before.

This morning I tightened it and checked the other fuel line fasteners at the pump and at the filter housing. Was able to get the housing fasteners snugged a little (not too much, but they needed it just a little) and the pump's are tight enough.

I will drive today and check see, and post new reality. I don't want to start dropping into expensive dealers and shops to start troubleshooting unless it is really necessary.

I'm away from home base and I don't have a home base diesel mechanic anyway.

Questions...

What might be my causes?

Might a loose filter housing create a condition (higher/lower pressure/suck air/etc.) prior to the pump that might cause the condition at light throttle/demand?

Can driving a little longer on a stumble like this create "serious problems"? In other words, does this thing need to go into the shop immediately or since it's not acting up at higher demand/load am I okay to continue driving and check the results today of that tightened filter housing to see if that did it?

Would the earlier intermittent condition perhaps be injectors getting cleaned up and now dropping of pieces of **** like gall stones? If so, maybe I just have to live with the stumble until it cleans up? Like I said, there seems to be a worse/better stumble at different times, even to the point where the problem was hardle noticeable.

[jmckelvy]

Another electrical harness to check is the one running next to the AC compressor. There have been reported instances of chaffing of some of the wires in the harness and causing similar symptoms.

[Dave_Pete]

My truck today wasn't the same truck as yesterday. Oh sure there was a rough or stumble as previously described, but most of the day I was trying to identify if it was the truck, or the road. (No it was the truck, but that illustrates the difference today).

It's Saturday and no diesel mechanics are staffed at dealers. We kept on down the road. What did I do to the truck last night?

In preparation to speak with a mechanic this morning I checked oil level and smell - both good. I checked air filter - good. I looked over that little heater hose behind the turbo on these engines that leak. See before this trip I replaced it, so checked it and things near it, like disturbed electrical connections. Did the same near the fuel filter because changed it before this trip. While there I checked two electrical connections associated with fuel. Wiggled, pushed tighter.

After such a better day, found our next Walmart for the night and went back under the hood. I carefully released four electrical connection retention clips and pulled each connection, one at the fuel pump, one at the fuel rail and two at the fuel filter. Sprayed electrical cleaner on each, applied dielectric grease, put them all back together.

Will try it again tomorrow, Sunday. Keep fingers crossed! If ANY feel of even slight stumble, I'll probably dealer it Monday for diagnostics.

[Dave_Pete]

Thanks okiejoe. Just got off the phone with a Cummins center in Rockport, IL. He said 2006 too new for diagnostic at other than dealer. He thinks maybe injector too. Was very helpful in discussions.

Hitting dealer next for diagnostics. Go from there. Will let you know the results.

Incidentally, he said no check engine because within tolerances, but still display starting a of failures. Not an uncommon situation.

[FlatBroke]

Not the same brand but my Dmax was doing the same thing. New injectors cured that and the longer crank to start problem.

[okiejoe]

OK, I have a 2006 5.9 and had the very same problems, No check engine light either, took it to dealer and they put in on the computer and discovered the #3 injector was misfiring (why no check engine is beyond me) dealers price for an injector was $702.00 just for the part so before I gave the dealer the go ahead I checked a local diesel/Turbo shop that has a great reputation so I took it to them and their computer showed the same thing. Their price was $350.00 for the very same injector that the dealer has (Bosch) so I bit the bullit and not only had that injector replaced but had them all replaced and new fuel tubes and had the valves adjusted too. Yes the bill was steep but after that it ran great. Then 16 months later the very same injector failed (this time it gave a check engine light), took it to the dealer and their computer verified that. I mentioned to the service manager that was the same injector that went bad the first time so he checked all electrical and harnesses and still the computer showed #3 failing, I had them pull the injector and I took it to the diesel shop that put it in 16 months earlier and they put it on their tester and found the electronic solenoid on top of the injector went bad so they gave me a new one at their cost since it was barley out of warranty and I took it back to dealer and they installed it and I am up and running. With all that said its probably a bad injector, don't waste money guessing and installing parts just let the dealer put it on their computer. But still not sure why the very same injector went out in 30 thousand miles after being replaced. Original lasted 140,000 miles. well we will just have to wait and see if it does it again.

Good luck

[Dave_Pete]

Thanks guys. No changes on drive today. Fuel and air filters (paper disposable) new 2400 miles ago at start of trip and air looks good.

Dirty fuel filter, bad load of fuel or inadvertently loading on bio fuel unlikely due to...

Several tank fulls since problems started

Great performance at higher load and demand

The problem is at light load (less fuel demand) like perhaps a throttle position sensor or other sensor (computer).

I can't troubleshoot this on the road. Guess I'll have to interrupt the trip.

[drcook]

here is a link to a forum dedicated to your combination

http://www.thedieselgarage.com/forums/127-5-9l-cummins-2003-2007-5/

join and ask there. typically, there are lots of brand/engine specific knowledge in those sub-forums

[Turtle_n_Peeps]

My call; your going to need new injectors. Take them out and have them pop tested.

Did the exhaust smell fuelly when you had the white smoke deal going on? Take the dip stick out and smell the oil. Does it smell fuelly? You can also do a paper towel test on the oil.

[DirtyOil]

White smoke at start up, with cooler ambient temperatures is normal.

Try cycling the grid heater a second time before starting, if that doesn't solve it, then it could be one or more of the following:

- poor fuel quality, low cetane, Bio fuel percentage to high

- inlet temp too low

- coolant temp low

- low compression

- ignition timing (cam position sensor issues)

- fuel injection issues, plugged/leaking injector (check engine oil level, has it gone up, does it smell like diesel fuel), change the fuel filter, have a injector flow test performed

- are you running a programmer, if so set it back to "factory settings"

That "stumble" you talk of, does it sound like a gas engine with a race/wild cam... kind of like a "looping" rough idle, one would see in Muscle cars? If so, you have an injector or more plugging off.
How many miles on the truck, have you had the injectors redone yet?

[drcook]

Diesel-Kleen will help clean out the system. As said above, when was the last time you changed the fuel filter ?

What kind of air-filter do you have ? Are you by chance running an after market one that is oiled ? If so, the MAF might need cleaned. If not, the MAF still might need cleaned. If you clean it, use MAF cleaner and don't touch the wire.

The fuel filters on these late model diesels do quite a good job about filtering out crud. They have to. The injectors run at such high pressure, that particles would erode the injector tips. My 04.5 Duramax runs at 22,000 psi. As such they do get plugged up. A load of dirty fuel can cause performance issues. I carry extra fuel filters when I travel just in case.

[45Ricochet]

How many miles?
Sounds like a fuel system issue. Hope tightening the filter solves your issue. Have you been using bio diesel? I saw a post from someone who had to fill up with B20 and his truck is only rated for B5. That could be the problem also.
You might try a quart of Opti-Lube to help clean up any injector issue that might be starting. Let us know what you find out.
How is your air filter? Rodents love the air boxes on those trucks.

[Triker33]

Dirty Fuel filter?
Lift Pump going bad?
Small leak in a fuel hose letting some air in it?