2013 Ram Intermittent Stumbling From Stop

[Will_TX]

My 2013 Ram 3500 with 115,000 miles is having an issue. No mods, no tuning.

When first accelerating from a stop, the engine will begin to speed up but then "stumble" as if starving for fuel for a second or less. Then it picks right back up like normal. This seems to happen less often when I am very gentle on the throttle. It only happens from a stop. At any speed greater than a stop, I have no issues.

This has been occurring for a year or so but has gotten more frequent in the last two weeks.

From what I have read this could be an issue with the fuel control actuator/solenoid/FCA. I am curious if anything else could lead to this problem before I fire up the parts cannon. Another cause some people have suggested is bad fuel or filters. My company sells fuel and my pickup and trucks at work fill up from the same bulk tank. No other vehicle has issues with the diesel. I am confident the filters are good since I got them from Geno's Garage. Mopar F/W seperator and Fleetguard FF53000 fuel filter. Both filters were changed ~5000 miles ago.

I tried some data logging from AlfaOBD for the actual rail pressure and the commanded rail pressure. You can see how the rail pressure reacts to the commanded rail pressure and throttle position. I marked green lines where there are discrepancies. You can see how the rail pressure drops out when the commanded pressure increases rapidly. The first four screenshots are from a stop. The last one is at 75mph with the cruise control on.

Any other suggestions to look into before throwing $200 parts at it?

View attachment 140977

 

[Lordsman]

I'll answer back since no one else has yet. My 2014 acted a lot like yours but mainly when cold outside. I replaced the FCA with one from Geno's and problems went away. Since you're not getting commanded rail pressure all the time that would be the FCA failing to send the proper signal to the CP3. With that said, there are many here on this site that are far more knowledgeable than I. If you do buy a new FCA buy from a reputable place like Geno's because there are a lot of fake ones out there. Mine a few years ago was $160 or so and you can change it out in 15 minutes

 

[Will_TX]

I'll answer back since no one else has yet. My 2014 acted a lot like yours but mainly when cold outside. I replaced the FCA with one from Geno's and problems went away. Since you're not getting commanded rail pressure all the time that would be the FCA failing to send the proper signal to the CP3. With that said, there are many here on this site that are far more knowledgeable than I. If you do buy a new FCA buy from a reputable place like Geno's because there are a lot of fake ones out there. Mine a few years ago was $160 or so and you can change it out in 15 minutes

Thanks for the reply. I went ahead and ordered the FCA along with some filters from Geno's. I suspect the diagnosis is correct but you never know.

 

[Will_TX]

I'll answer back since no one else has yet. My 2014 acted a lot like yours but mainly when cold outside. I replaced the FCA with one from Geno's and problems went away. Since you're not getting commanded rail pressure all the time that would be the FCA failing to send the proper signal to the CP3. With that said, there are many here on this site that are far more knowledgeable than I. If you do buy a new FCA buy from a reputable place like Geno's because there are a lot of fake ones out there. Mine a few years ago was $160 or so and you can change it out in 15 minutes

That only thing that wasn't obvious to me was how to unhook the connector. Seems the key part is on the bottom side and impossible to see. Any tips on that?

 

[Lordsman]

I believe you push on the tab to release it. I may have taken mine off first to gain better access to the connector. Having an extended T25 torx bit helps get the FCA off then you can use the new allen screws that comes with the new one. There are you tube videos on this, I like the Motor City Mechanic guy.

 

[Will_TX]

So I replaced the FCA with one from Geno's. Seems to have stopped the symptoms I was experiencing.

Some notes:
An extended T25 and an extended 4mm allex (if using the FCA from Geno's) makes the job much easier. You can do it with small bits just clearance is barely enough. MY original bolts were not hard to get off. They did have some kind of loctite on them but it seems to have been very weak after 11 years and 120k miles.

I did mess up by forgetting the plug the new FCA in. I started the truck and got a fault code and ignition/lightning bolt on the cluster. It gave a message about servicing the electronic ignition system I believe. Turned the truck off and plugged in the FCA. Started it again and tried to clear codes but the fault stayed. I went ahead and drove 12 miles home. Truck ran fine but acted like fuel pressure was minimal (get it to 75 but had very little force behind acceleration). After letting the truck cool off I started it again, unplugged the FCA, rail pressure shot up to 15,000 psi (from ~4,000) and the engine clearly changed tune. Plugged the FCA back in after about 2 seconds and rail pressure stabilized and fell a few seconds later. The warning light/message was gone and the code was able to be cleared. Now it accelerates like it should.

 

[Lordsman]

Glad you got it running right!