DIY Fuel Control Actuator Mod

[JJPage]

I removed my FCA today and performed the modification to the piston as noted on Relentless Diesels website. I did not do the orifice mods to the back of the pump.



First off, if you want more power and thats all you are looking for, it certainly accomplishes that, at least down low in the powerband.



When I first started it up, it rattled like crazy, rail pressure @ 15k idling in neutral, sounds similar to a 12V.



Drivability appeared OK... at first, I cannot take off from a stop without leaving a huge puff of smoke. My shifts are harsher, (I believe it is not de-fueling as much between gears). Once it is in third lockup or fourth lockup, it will not shift down, unless I SMASH the pedal to the floor. If I roll into it, even hard, still no downshift, and tons of black smoke(no need for a mystery switch), I can not believe this would work out towing my trailer, as my EGT's went over 1500.



Smarty/mild tq program/sw#5, TST 5/0, EZ 2. From a dead stop, WOT, I pulled my rail pressure down to 12k from about 1900rpm to 2600rpm until it started to recover, and never got over 20k until I backed out of it, and then it spiked to 26k. I turned my TST off, and very little difference. I tried this several times to be sure, it is hard to watch all the gauges at the same time.



This would probably be ok on a dyno for some cheap Hp gains, but as a daily driver, I don't recommend it. I have ordered a new FCA from Cummins, (#4932457)$90. 00.



Just wanted to share my experience! Jess

 

[Prairie Dog]

Good post, thanks for the info. It may keep someone like me from making a big mistake!



Scotty

 

[HighRanger]

15k at idle, when all the stuff started happening on my truck rail pressure was 27k at idle. Talk about sounding like an ol 12 valver. I just replaced the fca, cp3, ecm, and some other sensor, and wiring harness. Truck runs better now.

 

[JJPage]

Tomorrow, I will set Smarty back to stock, turn TST and EZ to "0".



I will give this "MOD" a fair shake, I will start slowly, with Smarty @ sw#1, and work up from there, adding different combinations in the smallest increments.



I will see if I can find a "place" I can live with, because this mod gives you a lot of extra fuel (probably as much as the original Smarty). I did this mod, and then failed to turn everything down



I am still not quite sure why this affects the downshifting of the trans???? Any thoughts? I have a few, just not ready to say out loud...



Jess

 

[PBax]

Chris himself at Relentless Diesel did this mod to my truck today. It simply did not work on my truck. The first FCA was modded pretty radically and rail pressure surged bad under throttle. Tried another FCA, modded but not so aggressively. It too surged but not as bad. Finally had to put a stock FCA back in and he gave me my money back without even thinking about it. He wouldn't keep a dime for his time spent.



my truck was the first truck that this has happened on to his knowledge. He had modded LOTS of these pumps and never run into this problem before. No one knows why it doesn't work on my truck... .....



I'm not knocking the mod or Chris, but it happened to me. Chris is a stand up guy and will see me again for air mods.

 

[JJPage]

Mine did not surge(rail pressure), but it did "BURST" "MISS', I believe, run out of fuel in mid range a couple of times (just like it used to do w/smarty/tst mix). I turned the HP down on the TST but the same results.



The TST and the Smarty both fuel heavy down low, stock CP3 cannot keep up. Thats why I am not able to run the Smarty, with the TST on any TQ above 0. (As long as I leave the TQ on the TST to 0 = good).



I am thinking that the FCA mod is is supplying all the fuel the stock CP3 can handle, just like the Smarty/TST stack... The stock CP3 is not capable of delivering the fuel to the rail.



As far as high EGT's, I am at my limits running empty, when towing, I should be producing higher boost, which should result in lower EGT's. ???

 

[JJPage]

Chris himself at Relentless Diesel did this mod to my truck today. It simply did not work on my truck. The first FCA was modded pretty radically and rail pressure surged bad under throttle. Tried another FCA, modded but not so aggressively. It too surged but not as bad. Finally had to put a stock FCA back in and he gave me my money back without even thinking about it. He wouldn't keep a dime for his time spent.



my truck was the first truck that this has happened on to his knowledge. He had modded LOTS of these pumps and never run into this problem before. No one knows why it doesn't work on my truck... .....



I'm not knocking the mod or Chris, but it happened to me. Chris is a stand up guy and will see me again for air mods.

PBax, I am believing that it has something to do with the fact we have automatic transmissions, and the interface of electronics. The folks with Manual trans seem to be working better for them. (just like the original Smarty).

 

[Relentless Diesel]

If you have 15k rail pressure at idle your FCA is sticking!



After a modded FCA is installed, rail pressures at idle and cruise are unaffected UNLESS it's sticking.



Automatic transmission have nothing to do with it. Most all the trucks I've done this mod to are autos.



When the mod is done correctly there will be no funny sounds, or surges. It will drive and act as smooth as stock, just more fuel available when needed.



Pull it back apart. You should be able to watch the valve slide in and out freely as you turn it upside down and back. If you leave it upside down, the valve should fall out on the table with just a slight shake. If it doesn't, you have a burr somewhere that is causing it to stick.





Phil's truck yesterday was an entirely different problem. His truck had similar problems to what we've seen with some Stage 2 pumps in the past. I don't know exactly what it is, but my best guess at this point is the operating system in the ECM responds faster to rail pressure fluctuations in some trucks than others. Until yesterday I'd seen problems with stage 2 pumps, but never with a simple FCA mod. Hopefully this will lead us to a solution for everyone.

 

[CraigJones]

Does anybody know what size diameter holes to wire EDM cut for this mod ? Thanks

 

[PBax]

I didn't mean to suggest that the problem here is the same issue i have, but i was just saying that for the first time in history it simply did not work.



I knew there was a reason I didn't want to risk this mod myself without a spare FCA... . thats why i went to Chris. So for anyone else comtemplating this mod as a do-it-yourself, it would be a good idea to have a spare FCA on hand. For $90 its cheap insurance to know you can drive home at the end of the day.

 

[PBax]

oh yea that whole downshift issue in the trans... . thats something the Smarty does on my truck. Dont know why, but i could floor it and it would not down gear. Now running Scary Larry again, it downshifts fine. Go figure.

 

[JJPage]

If you have 15k rail pressure at idle your FCA is sticking!



After a modded FCA is installed, rail pressures at idle and cruise are unaffected UNLESS it's sticking.



Automatic transmission have nothing to do with it. Most all the trucks I've done this mod to are autos.



When the mod is done correctly there will be no funny sounds, or surges. It will drive and act as smooth as stock, just more fuel available when needed.



Pull it back apart. You should be able to watch the valve slide in and out freely as you turn it upside down and back. If you leave it upside down, the valve should fall out on the table with just a slight shake. If it doesn't, you have a burr somewhere that is causing it to stick.





Phil's truck yesterday was an entirely different problem. His truck had similar problems to what we've seen with some Stage 2 pumps in the past. I don't know exactly what it is, but my best guess at this point is the operating system in the ECM responds faster to rail pressure fluctuations in some trucks than others. Until yesterday I'd seen problems with stage 2 pumps, but never with a simple FCA mod. Hopefully this will lead us to a solution for everyone.

OK, I will pull it apart again, and I will POLISH the heck out of it!



I really did do a thorough job the first time, it would fall out, but I had to give it a hard tap.



I am trying to "alert" anyone doing this mod, what to expect, especially if you do not follow directions "to a tee"



The shifting behavior of my trans started exactly, exactly, after the mod, could be a coincidence. I am in correspondence w/DTT as we speak.

 

[JJPage]

Today, I disassembled my FCA again, repolished the piston, and made sure it was not sticking. The piston slides in and out just by tipping the FCA back and forth.



Reinstalled, start truck, 2650k rail pressure @ idle, this simply is not working for me and I believe I now know why.



I installed the new FCA from Cummins, my truck runs smoother than it ever has, my rail pressure is stable and it follows with my go pedal. I believe my original FCA was and has been faulty for some time.



Maybe when I get "steaky" again, I may try the mod with a new $100. 00 FCA, because it really did add LOW END TQ.



Oh, by the way, my trans is acting normal again???



Jess



Thank you to Relentless Diesel! I never meant to "DIS" your MOD, Thanks for the info.