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Hi All. I picked up an 04.5 earlier this year. I have plenty of experience with gas motors but this is my first turbo diesel. I needed it for towing -- it has a built trans and no blowby even though it has 284k miles. The price wasn't too bad so I went for it.

The truck starts quickly, no excess smoke. No apparent fuel leaks under the hood. No codes except for a wastegate circuit due to a bigger turbo. The problem I am having is the motor surges or oscillates when at a fairly steady speed. Truck has an Edge CS2 so I have been monitoring parameters from the ECM when the problem shows up. My biggest concern is that the fuel rail pressure oscillates pretty wildly when it starts to surge. The surging is less noticeable at lower speeds but occurs at 25 MPH when warming the truck up driving through the neighborhood. It also shows up around 35 MPH before shifting into 4th. I can baby it and get up to a cruise at a steady 55 MPH at 18kpsi rail pressure and everything seems fine. If I accelerate a little more and rail pressure goes over about 20kpsi the truck surges and rail pressure bounces rapidly in 5kpsi increments until I let off the throttle.

I thought it was a fuel delivery problem and the FASS is a little loud-Changed filters on the FASS, looked over lines and moved the siphon tube in the tank around to see if perhaps something was wrong. I disconnected the FCA and the CP3 generates 27kpsi at idle. I replaced the FCA and the PRV. No changes in symptoms. Replaced the regulator and spring in the FASS from the ball type to the machined aluminum pass through type. No Change. Finally got an electric gauge and put the sender in the FASS gauge port. I get a steady 18-19 psi when driving and no apparent dips on the low pressure side when the problem shows up. There is no smell of diesel in the cab or under the hood. No fuel leaks around the fuel lines that I can find. I pulled all the fuel feed lines and torqued the injector tubes to 42 ft. lb. per Todd at T&C Diesel. 5 of the 6 turned when torqued and I thought I may had solved the problem but still no change in surging symptoms. No smell of diesel on the dipstick and oil level is not going up - If anything it has gone down slightly since the last oil change.

The battery terminal connections were not great so I replaced the passenger side connectors and cleaned all the terminals and made sure the connections were good. However, the previous owner wasn't great with electrical work and there are some other gremlins that need to be addressed in the electrical realm.

I have read about other folks with similar problems on the forum and it turned out to be the APPS, AC Noise/torque converter lock/unlock or cracked fuel lines off the rail. I tried to rule out the APPS by monitoring throttle position on the Edge CS2. Never saw it bounce when truck was surging. Does that mean the APPS is OK?

I have a Digital Multi-meter. I need to do the AC noise test correctly but only had time to put it across the passenger side battery posts. I didn't observe too much noise but I'm not really measuring the correct thing. If it is AC noise from the alternator, would fuel pressure jump up and down like I'm observing?

One thing to note, the idle is not bad except for when it is cold outside. Then it has a not so subtle lope which happens every 30-45 seconds. When it happens I notice the under hood light dim and voltage drops from a steady 14.9V down to 13.5 V. That problem goes away once the truck has warmed up. Could that be an alternator problem?

Mods by previous owner: FASS Titanium, No CAT and 4" muffler, Head studs, 63/67 Tater Turbo, S&B cold air, S&B intake horn, 50HP over injectors (guessing they were installed less than 20k miles ago, I forget brand but not BBI), built auto transmission. I am currently running the stock tune.

I have been doing a bunch of reading and I'm not sure which test or step to do next. I have a Timbo APPS on the way and I'm ready to buy a Nations Alternator if that will fixing the problem. I really don't have money for new injectors so I'm going to be super bummed if that is the problem. What do you think is causing this?
 
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Your voltage swings and lights dimming are from your grid heater cycling. Totally normal.


5k PSI swings in rail pressure at steady 55mph is not normal.

1st step is to set your ECM back to stock with your EDGE CS2 programmer/monitor.

A modified FCA in the CP3 can also cause some surging in cold weather.
Is the CP3 stock?
Does the Cp3 have modified FCA? Bag of parts from Industrial Injection, Arson kit from Motorsport Diesel and others?

If you have any doubts about the FCA, a new stock one is recommended.
If you have any doubts about the Rail pressure relief valve, a replacement or a cheap block off cap for testing purposes can rule that out.


BTW, your wastegate DTC, due to your aftermarket turbo, can be easily resolved by a wastegate fooler.
Many companies make them, US$20 or so.

 
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This type of Problem has roots from Fan to Transmission. I can't remember if you told me if it surges when using Cruise control?
 

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Discussion Starter · #5 ·
Your voltage swings and lights dimming are from your grid heater cycling. Totally normal.


5k PSI swings in rail pressure at steady 55mph is not normal.

1st step is to set your ECM back to stock with your EDGE CS2 programmer/monitor.

A modified FCA in the CP3 can also cause some surging in cold weather.
Is the CP3 stock?
Does the Cp3 have modified FCA? Bag of parts from Industrial Injection, Arson kit from Motorsport Diesel and others?

If you have any doubts about the FCA, a new stock one is recommended.
If you have any doubts about the Rail pressure relief valve, a replacement or a cheap block off cap for testing purposes can rule that out.


BTW, your wastegate DTC, due to your aftermarket turbo, can be easily resolved by a wastegate fooler.
Many companies make them, US$20 or so.

Good to know know that dip in voltage is just the grid heater.

The FCA has been replaced with a new, unmodified Bosch unit. The PRV was replaced with a 30kpsi from Todd. The ECM is running on the stock tune.

The CP3 appears to have been replaced at some point as I do not see a Bosch tag on the side of it. I have no idea if it is a stock reman or modified unit. Other than checking for max psi with the FCA unhooked, is there any other way to test the CP3?

The surging problem was present in warmer months.
 

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Discussion Starter · #6 ·
This type of Problem has roots from Fan to Transmission. I can't remember if you told me if it surges when using Cruise control?
Cruise control doesn't work properly most of the time. Sometimes it will engage and then stops working moments later without any indication. Does the Torque Converter stay locked in cruise? Or does the computer take over the APPS?
 

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The PCM controls the CC on 2004.5 Fly by wire, 2003 was PCM controlled Servo- VIA cable. CP3s rarely cause surging problems, and when it does, its accompanied with other problems.
 

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Never heard of AC noise causing issue you are describing without other issues and codes shown on 3rd Gen.
If RP is bouncing sounds like you have a fuel issue, when a fuel issue happens trans will never lock converter or CC will not stay engaged as ECM is monitoring output speed sensor and RPM for constant values. Info on your trucks fuel and electrical sysytem found in
03 - 07 3rd Gen 5.9 Liter General Discussion | Dodge Cummins Diesel Forum (cumminsforum.com)
 
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Well you've eliminated most things at this point. How about the rail pressure sensor?
Unlikely but anything is possible at this point.


Resolve your wastegate DTC as above, resolve any other DTC's.

Then it's time to start diagnosing your unknown injectors as Rghavana mentioned earlier.

Balance tests, return flow tests, etc, etc.
 
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Never heard of AC noise causing issue you are describing without other issues and codes shown on 3rd Gen.
If RP is bouncing sounds like you have a fuel issue, when a fuel issue happens trans will never lock converter or CC will not stay engaged as ECM is monitoring output speed sensor and RPM for constant values. Info on your trucks fuel and electrical sysytem found in
03 - 07 3rd Gen 5.9 Liter General Discussion | Dodge Cummins Diesel Forum (cumminsforum.com)
It's not the Noise it's the harness connection, same for the fan Connection.....When shorted circuit(s) occur it may have an effect on FCA voltages, On My test Machine that's How We test FCA, pre-set switch will change the RP in less -1.50 Seconds.20K to 10K PSI with the push of a button Same RPM.

Years Back (Similar Problem) owner said Keep Truck until $5.000.00 spent, drive it every day likes its yours, it took 3 weeks Daily driving, He was happy to pay the $800.00, the problem was shorted 12V Cig Lighter.
 

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I am sure there are numerous oddball possible causes to what OP is describing, but IMO you start with the most common causes and perform appropiate test to rule it out.
Since he has no info on injectors and they were loose ie improperly installed, it leads me to question, the rest of the parts/installation, so next step is checking the rest of the installation with a simple return test.
I never mentioned throwing parts at the issue.
 

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Discussion Starter · #12 ·
Well you've eliminated most things at this point. How about the rail pressure sensor?
Unlikely but anything is possible at this point.


Resolve your wastegate DTC as above, resolve any other DTC's.

Then it's time to start diagnosing your unknown injectors as Rghavana mentioned earlier.

Balance tests, return flow tests, etc, etc.
I think the Rail Pressure sensor is working properly. I have been watching RP closely over the last two months; idle, cruise and max PSI (FCA unplugged at idle) read where they are supposed to. The surging also coincides precisely with rail pressure oscillation.
 

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Discussion Starter · #13 ·
I am sure there are numerous oddball possible causes to what OP is describing, but IMO you start with the most common causes and perform appropiate test to rule it out.
Since he has no info on injectors and they were loose ie improperly installed, it leads me to question, the rest of the parts/installation, so next step is checking the rest of the installation with a simple return test.
I never mentioned throwing parts at the issue.
I found the receipt for the injectors. Exergy 50 HP and were installed by a reputable shop. The injector tubes may have been torqued to 37 ft. lbs. which was the spec before Cummins updated it to 41 ft. lbs.

The thing about this problem is that the symptoms don't directly point to a single issue. I thought low pressure fuel delivery was suspect (the FASS is getting a bit loud). But I have all but ruled that out, unless of course the surging just happens to coincide with the refresh rate of my electric gauge (glow shift).

I do still need to do the injector flow test, but would expect drivability problems to show up across the range of driving conditions and not just at steady speeds. I also don't have some of the other symptoms typical of bad injectors. Idle is smooth and it starts right up.
 

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Discussion Starter · #14 ·
It's not the Noise it's the harness connection, same for the fan Connection.....When shorted circuit(s) occur it may have an effect on FCA voltages, On My test Machine that's How We test FCA, pre-set switch will change the RP in less -1.50 Seconds.20K to 10K PSI with the push of a button Same RPM.

Years Back (Similar Problem) owner said Keep Truck until $5.000.00 spent, drive it every day likes its yours, it took 3 weeks Daily driving, He was happy to pay the $800.00, the problem was shorted 12V Cig Lighter.
So you're telling me I may have inherited an electrical nightmare that no one wants to deal with? Timing is certainly bad for this kind of problem. I'm having to sell my gas daily driver to raise funds and the 2500 has to be driven all winter.

The truck does keep popping LH parking light bulbs. The LH headlight bulb (low beam only) just went out as well. As for other electrical problems, the Passenger's rear power door lock doesn't work (master switch was replaced as well as the actuator). Also, the ABS light and E-brake occasionally come on and go off with no intervention on my part. The power mirrors do not work and the aforementioned Cruise Control doesn't work.

Any suggestions on where I should start looking?
 

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Save some money. Hold off on the APPS replacement, easy to test those while driving with your DVM.

Start by checking all the connections, wiring n solder joints in the IPM Integrated Power Module IPM common name fuse box under hood driver side.
Low IQ prior owners often butcher these, also low quality built. Not rugged for a pickup especially the current power draws in a Ram. Lots of cold solders, broken wires, corrosion ad naseum.
Leads to lots of problems in any electrical electronics area in a Ram. Plays hell with steady battery voltage to the EMM. EMM requires fairly steady 12v+- with no rapid V changes. EMM produces a regulated 5V that has to be rock solid, supplies all the sensors on the motor including the RPS with a base reference power. Wild fluctuations on the 5v regulated cause wild swings on the sensors output control signal to the EMM.

Also stick with the stock OEM Bosch alternator, control circuitry in the Bosch and the EMM are designed to be compatible. Most of the aftermarket don't control the alternator correctly, burn out components batteries EMM
Garbage in shhiittee out
 

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Exergy makes new and reman injectors, hopefully new injectors and new connector tubes.
Can try and monitor what is actual vs demanded rail pressure, when issue happens.
Holding steady RP at higher rpm on cruise to me is when faults are more likely to occur.
Can go to newbies guide get FSM for your truck, read/learn how to troubleshoot electrical gremlins.
Newbies guide to your new to you truck
 
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