Cummins Ram Hard Start & Drivability Issues

Zachary Mobile Technician Austin, Texas Posted   Latest   Edited  
Updated
Driveability
Heavy Duty
2008 Dodge Ram 2500 Laramie 6.7L (A) 6-spd (G56)
Hard To Start
Lack of Power

Good morning all and thanks in advance for taking the time to read and respond. This is a really long one I know but I wanted to try and give you all the information I have and show the extent to which I've tested this thing.

This is a first time customer for me who I got on a referral so the only history I have on the truck is what I've been told. Customer's initial concern was the truck wouldn't start unless it got a shot of ether first. He told me that they'd recently had the e.g.r. and DPF systems deleted and the head gasket replaced. The truck has apparently had a tuner on it for quite some time but supposedly doesn't get cranked up high. They use this truck mainly to pull a boat as the customer owns a company which builds and maintains boat docks. After those repairs were done, I'm told the mechanic working on it messed something up putting the tune back on the ECM and erased it. It wound up getting a remanufactured aftermarket ECM as the Dodge dealer told them it would be $2200 for them to fix that issue. After that the truck ran again on stock tune but the customer decided there wasn't enough power and put the tune back in. It ran for about another week until they were towing a boat and the c.e.l. came on. It was setting a code for low supply pump pressure so the customer's employees changed the lift pump and fuel filter. After this was done, the truck wouldn't start without a shot of ether. I'm getting conflicting information here but I believe the truck still started prior to the lift pump replacement but was hard to do so. When I got to it initially, I ran a system scan and retrieved the following codes: P0405, P0606, P0031, P0037, P061C, P0335, P245C, & P144E. When the codes were cleared, the P0335 & the P061C came back immediately. I attempted to start the truck while monitoring fuel pressure & FCA pids and got the first video. As you can see, the fuel pressure appears to be building but right when you'd think it would start it didn't. I assume the ECM rpm pid is being calculated off the cam sensor because the RPM from crank sensor pid is stuck at 0. It does a weird thing where it kind of stops cranking and even seems to kick back at times. I thought perhaps due to an erratic crank sensor signal so I scoped directly at the ecm and got the second capture you see. This looked normal to me despite the fact that the ECM doesn't appear to recognize it. In addition, I didn't believe that to be the root cause as this system should start on just the cam sensor signal. Just to rule out some simple things, I unplugged the rail pressure sensor, the crank sensor, and the FCA one at a time while attempting to start with no change. I also rolled the ECM tune back to "stock" with the customer's tuner to try and limit variables. I initially though this was going to be an issue building high pressure fuel but the rail pressure pid threw me as it was climbing so high while cranking. I went ahead and got it started using ether and the truck seemed to run fine in the bay. I took it for a test drive while monitoring fuel pressure and FCA pids and got the third capture you see under load. Ok great I thought. Now we're on the right track. The ECM also set the following codes when this issue occurred: P1011, P000F, & P0087. I suspected these were the codes the customer had seen when they were told to change the low pressure pump and filter. I performed an in bay volume test at the high pressure pump inlet, at the fuel filter inlet, and right at the output fitting of the supply pump. In all cases, the aftermarket pump put out between 22-24 p.s.i. which seemed high compared to what I was used to on these. The volume however was always under every spec I've found for these only putting out about 10 ounces in 15 seconds. I test drove the truck with the low pressure gauge taped to the windshield and the pressure would be shaky at all times and then drop almost to zero under fault conditions. Once for a brief period the symptoms cleared up but then reappeared indefinitely. After verifying good power and ground to the pump, I informed the customer that there was either a restriction in the tank or the new supply pump was bad. Once I got the approval, I dropped the tank and found minimal amounts of dirt inside. Just the same, I cleaned it out and installed a new Delphi pump. After reassembling everything, the truck still required ether to start however things changed a bit. For starters, the supply pressure rose to about 30-32 p.s.i. and I was getting closer to abut 13-14 ounces of fuel in 10 seconds. For the most part, the high pressure pump was able to keep up with demand and I never saw the low pressure dip under about 15-17 p.s.i. even when there was an issue. I noticed an abrupt change on the scanner this time and though perhaps the regulator was sticking. When I got it back I could get the truck to start after one or two tries without ether. I had someone crank it while tapping on the FCA and it would start first try every time. I pulled the FCA and there was no metal debris or rust on it. I ordered the part and came back out to install it but wanted to verify one more time. I couldn't get it to start without ether even if I tapped on the FCA. I don't honestly remember at what point I'd done this initially but after replacing the low pressure pump, I performed the pressure limiting valve test as well. I was showing that valve was leaking during cranking so I replaced it with a brand new Bosch part and got the exact same result. After I came back to replace the regulator, I repeated this test and it wasn't leaking. I pulled the cascade overflow valve and found that the plunger was really weak and easy to push. I checked for fuel return from the COV while cranking and there was flow. It's my understanding this valve shouldn't be returning flow while cranking. I performed the COV & injector return rate tests and got the following results with the FCA unplugged. 175 mL in 30 seconds for the injectors and a little over a liter in 60 seconds for the COV. I found 3 different specs (160, 180, & 210 mL) for injector return rate test and the 175 falls right between the lowest and the middle spec. Just to be sure the limiting valve didn't go to leaking, I checked it again and it was in fact leaking which of course will skew my COV return rate result. I installed a race valve in place of the limiting valve and the truck wouldn't even build high pressure fuel at all. At this point I was really at a loss as I seemed to have several failed results but inconclusive resolutions. I can't find the COV separate for this pump and I definitely don't want to shot gun something like that. This truck is kicking my butt and I fear I've gotten tunnel vision. There may be some things that I've leaving out but I believe I covered most of it. Sorry for the ridiculously long post but this thing has been kind of a saga. I truly appreciate any and all input. Hope everyone is having a great Monday!

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George Owner/Technician
Skagway, Alaska
George Default
 

The last 1 I worked on ended up needing injectors. I was told by 1 of the diesel shops that the best way to prove this was to shoot some silcone spray into the intake while some one cranks it. Take out 1 of the bolts that goes through into the intake below the intake heaters. If it starts right up , it needs injectors. Hope this will help[ you.

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

That's interesting George. I wonder what the thought process is there. Perhaps that the silicone spray acts like ether? Wouldn't a weak high pressure pump or excessive return fuel act the same way if so? Don't mean to question the advice I'm just trying to understand the logic behind what they told you. In any case, I really appreciate your input.

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George Owner/Technician
Skagway, Alaska
George Default
 

Zach no worries there. I was just passing on what a quick test was from a diesel shop. If you spray it into the intake and it stays running then it's injectors. If it doesn't stay running then it's time to look elsewhere. Another diesel shop told me on an international to pull the exhaust and see what is happening while cranking. I don't know how well this will work on the cummins. On the…

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

Definitely appreciate that George. No such things as too many weapons in the diagnostic arsenal. I hadn't heard of the silicone trick but I like the idea of something less harsh than the ether. I'll look into that as well and see what I find. Once again thanks for your input. Having this community is invaluable in times like these.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Go back to square #1 and start over. It doesn't matter what work has been done to the vehicle. start with a new slate. If the ECM has had a tune put in, then reflash the ECM back to stock software. Now, you at least have a baseline to start with. For this engine to start, it needs a fuel supply of good diesel, with no air in the system. It also needs a cranking speed over 150 RPM, with around 11…

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

Thank you Albin for your response. I agree, it feels like I'm wandering around in the dark. I would like to ask a couple of follow up questions for clarity. When you say reflash the ECM back to stock I assume you mean with a factory scan tool? I did roll the tune back to stock with the customer's tuner but I've been told before that this isn't always the same as an authentic flash file from the…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Thanks for the reply. I went back & viewed the data in SCC. Nice data!! That showed exactly what I was looking for. The data shows the system is capable of making the correct fuel pressure. You are correct that many times when a tune is removed, it still leaves stuff in that shouldn't be. You can reflash these processors with a J2534 tool if need be. Since you have the correct fuel…

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

Thank you Albin...That's a really good point. I will definitely check for excess blow-by however there's 2 things that still bother me. The first is the pressure limiting valve was leaking fuel when tested and I got the exact same result with a brand new part. The second are the instances where the high pressure actual deviated so far from the desired. It seemed to be better with the new supply…

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Zachary Mobile Technician
Austin, Texas
Zachary Update
   

Update Made it back out to the truck today finally and here's what I know. Absolutely no smoke coming from the engine with the breather cap removed and no pressure felt either. I wasn't 100% on the bolts you meant for the intake George (I assume the ones that point straight down through the plates and grid heaters?) but I shot silicone spray in through the opening at the throttle body and it…

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Zachary Mobile Technician
Austin, Texas
Zachary Default
 

Final Update Hello again everyone. My apologies for the long delay in response. I wanted to be completely sure of this one before I posted, and it took over a month to get the ECM back from the company with who it was under warranty. That's a whole other fiasco that I won't bore you with. I can say that I'm glad I wasn't the one who originally provided the ECM. Long story short, verified powers…

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Thanks for the update

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