miss at cold start & getting worse

[msparker]

My 2004. 5 3500 started missing 1-2 cylinders on cold starts last winter. (203k on the clock) The engine also has a slight miss or hesitation that you can pick up after it is up to temp on occasion. Fuel mileage has dropped, and there is slightly excess exhaust smoke. The engine seems to "run good" have close to normal power at full throttle. First check at the local diesel shop said "bad injectors" The injectors are DDP 1659, which DDP calls 50HP, that have approx 50 k on them. We pulled the injectors and sent them to DDP and they tested good. The injector tubes look good and were installed and torqued properly. Rechecked and adjusted valve lash at this time as well. Also have installed new lift pump, and of course fuel filters. (inline 5 micron and the oem) I have an Auto Enginuity scan tool, but I cannot get it to run a "cylinder contribution test". The scan tool will give me a lot of info from the ecm, but i do not know what the baseline numbers should be. Does a factory service manual have spec's for rail pressures and all the other data you can pull form the ecm? All sensors and electrical are original. Need some help!

 

[Bob4x4]

The fsm does not give values. If the injectors are good,the install was good time for a compression/leak down test

 

[msparker]

Thanks Bob, and i agree, it would have been good to check compression leak down at that time. I am wondering why i got only one reply to this post however. It seems like most ?? get several responses, did i post correctly?

 

[cerberusiam]

Weather is nice and everybody is playing.

Call AutoEnginuity about the cylinder contribution test and see if you can resolve that. I was planning on buying that software but not if it has issues with the needed pieces like that.

Rail pressure varies based on temp and throttle input. At an idle, 5500 to 6500 psi is normal. Stock engine WOT throttle probably not more than 21k psi depending on load. Won't tell you much about the injectors but it will tell you if the CP-3 is keeping up and you have potential leaks, sort of.

The symptoms sounds like injectors. I would get a cylinder contribution test done some way if you cannot get the software to work. Next step would be an injector return flow test to see if there are issues with the injector flow. If you are getting excess smoke driving and the fue mileage has tanked it is a good bet there is an injector going south and the testing is not catching it. Testing these injectors is an art and you never know who is doing it and their experience. You may not even see that with a return flow test. Missing at an idle should catch something with a cylinder contribution test.

You might try the CRC or SeaFoam injector cleaner process just to verify they are not sticking. Drain the filter housing of fuel and fill it with your choice of cleaner. Start the engine and let it idle for a minute or so and let it set overnight. Worth a shot at this point.

 

[JJPage]

msp

I see you have Dynomite injectors, if they tested and said good, then rule the injectors out, but still could be installation issue. Do you also have any black boxes or downloaders? Could be a bad injector harness or vc gasket...

If you have an Edge product, especially an EZ, remove it then check for results. Are your batteries up to snuff? I take it your scan tool is showing no codes, how about the key check? both for codes and if you have a Grey key w/chip?

Take time to fill out your truck's sig in the user control panel, list your mods/upgrades if any, makes it easier to help diagnose. Many on here are willing to help, but like cerb stated, the weather is nice...

Jess

 

[msparker]

Yes, i need to get the cylinder test to run. I got some feedback from AutoEnginuity, and i have to "try it again" this weekend. I also need to test each cylinder separately with the scan tool and see if i can isolate which cylinder(s) is/are weak. Thanks for the feedback on rail pressure, that is about what i am seeing on the scan tool. Is there a source for other baseline data? Bob4x4 said it is not in the fsm, so i won't spend the money on that. All electronics are bone stock and the batteries are good. I agree suspicion on the injector installation, i just hate to pull it back apart until i know more.

Thanks guys.

 

[cerberusiam]

Dodge has the baseline data for testing, probably from Cummins and ultimately Bosch. Not in the FSM and probably only in internal tech bulletins. Ultimately, it was likely all copied from Cummins anyway as they developed the engine and the programs that run the fuel maps.

Don't be too quick to ignore a bad injector as the issue. The rumors indicate that DDP may not be the same business it was a while ago and that could have a direct effect on their ability to properly diagnose. Besides, the typical response form a vendor is there is nothing wrong with the injectors. They all do it and they have all been caught out on it.

The systems of increased smoke and dropping mileage are pretty indicative of an internal injector issue. If there was an install problem with the cross over tubes you woud see rail pressure issues, hard starts, possibly bucking and jerking under load, etc. A injector with a cross over tube problem is probably not going to miss at an idle because it will likely never start without extreme measures, like starting fluid. You should also see a hard start warm if they are loosening. If you have any of the above symptoms then an install problem is in the realm of possibility. The only other thing I can think of that would allow the injectors to be good and still have problems is the edge flters in the cross over tubes are plugged on some. That could cause a miss at idle, might cause some smoke driving, and maybe cause excess fuel consumption. I would think along with that you would see some abnormal EGT's and higher than normal pressures at time as the ECU tries to compensate.

Try to get a cylinder contribution test would be my first step. An injector return flow test will tell you if the injectors are bypassing too much fuel or injector is cracked or cross over tube is loose, leaking or cracked. Won't completely nail it down but it will indicate a problem. I would do the injector cleaner routine just to cover your bases. One or two injectors slightly dirty and hanging will cause all your problems.