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Thread: knock or miss on take off

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    Basic Member lovemydiesels's Avatar

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    knock or miss on take off

    Hi guys, totally new here. i have a 2015 5500. i bought it deleted, studded, tuned with RACEME Ultra, BBI stg 1.5 injectors. it is about to turn 80k miles, i have put 7k of those on it. i pull very heavy so i run on the 30hp tune. i installed a FASS titanium 165 in the last 1500 miles with a FASS sump and top draw kit at first. The pump made a lot of noise and the truck was running worse than before but with less smoke. i ran the tank low and switched to drawing fuel on the bottom directly at the sump. The truck runs much better and reduced the smoke more. My problem is now it seems to have a miss or knock intermittently only off idle. it doesn't do it any other time that i have noticed, only from a stop after idling, like at a stop sign or light. if i throttle slow and easy, it is normal and smokeless. if i have waited at idle and try to take off anything moderate to floored it falls flat on its face, makes a distinct knock, it sounds like a single miss fire but all power hesitates while blowing a solid black puff and then proceeds to accelerate as desired. Anyone have any similar scenarios? Haven't had the truck looked at, the Fass is the only mod i have performed besides a mechanical boost gauge. Not throwing codes or CEL, does it empty and loaded/towing


  2. Top Of Page | #2
    TexNeck's Avatar

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    Re: knock or miss on take off

    Any idea what your rail pressure is doing when this is happening? It sounds to me like it would be related to the tuning or FCA more so than the fass system causing the issue

    2013 Ram 2500
    John 3:16 - Philippians 4:13

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  3. Top Of Page | #3
    Basic Member lovemydiesels's Avatar

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    Re: knock or miss on take off

    I will check the RP. For some reason i never thought of that. I wouldn't think it was the FASS because ive installed them on multiple trucks, it just happened to be the only thing I had changed in the time frame the problem arose. I have also been meaning to clean the MAP and MAF sensors since idk how long the choking equipment was on I thought the guy said 40 some K miles so i wouldn't be surprised if the MAP is sooted up. THX


  4. Top Of Page | #4
    Basic Member lovemydiesels's Avatar

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    Re: knock or miss on take off

    The rail pressure drops down into the 2000s


  5. Top Of Page | #5
    TexNeck's Avatar

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    Re: knock or miss on take off

    That’s no bueno. My guess is you need to replace the FCA (fuel control actuator) on the CP3. It was easy on my 5.9 I believe just 3 torx and connector - I believe if you remove it shake the sensor and if you hear a rattle it is bad.

    Buy a replacement from Cummins- about 1/2 price of the dealer

    2013 Ram 2500
    John 3:16 - Philippians 4:13

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  6. Top Of Page | #6
    Old & Grumpy! Polaraco's Avatar

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    Re: knock or miss on take off

    Low lift pump peformance can do that too. CP3's are strange beasts. Some work better in ths sceanario than others This includes fuel filters. But not in this case. You're going to have to check the pressure. A draw straw should have been plenty. The pump being super noisey was a vacuume leak in your plumbing.

    I don't like sumps because you get all the dirt and water in the bottom of the tank. Fuel filters are not perfect. Just saying dirt can get past them. Ask Air Dog. Bast&^%$#s

    Tex could be right, or there is a restriction somewhere. Since the install is new, I'd be looking at that first. You need a pressure gauge. A oil pressure gauge will work. Just need to plumb in a T on the discharge side. It's best at the CP3. They make banjo fittings already tapped with an 1/8 NPT port


    2003- 3500 RWD Automatic.
    S & B intake, BD Intercooler, Pusher Air Horn, MM3 Double R Tuning, Turbo Timer, electric Flex-a-lite fans, FASS 95,
    50 HP tips, upgrade to 351 turbo, 3.42 gears, Twin air compressors, air bags, Remote dual oil filters, Hellwig sway bar, Front Winch. Home made Fuel Heater, BD Exhaust brake with Torque Lock. Tons of TLC

  7. Thanks TexNeck thanked for this post
  8. Top Of Page | #7
    Basic Member lovemydiesels's Avatar

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    Re: knock or miss on take off

    Teaneck- thank you, that seems pretty logical and I suppose something could have entered the system durong install. If I'm already buying parts, should I just get an arson 3 kit to supply my injectors for effectively? Could that be part of my problem? Polaraco- Thank you for the tip, that was something I planned on adding to my setup permanently anyway. The only part I'm not so sure about is I know there is decent pressure becuase i did a bucket test b4 and after my draw straw to dump. I also removed and cleaned the fuel tank. I thought it had a loose fill or vent hose so I pulled it. To my surprise it had a little metal tab siliconed to the top of the tank. I removed it realized that there was melted holes along the top of it. It's directly under the gooseneck hitch in My CM flatbed. Those ding dongs must have had a new welder that didnt cover the tank for spatter and blow outs. So after all of that i would think the dump would stay pretty clean. Also both of my duramax trucks didnt come with a lift pump at all from the factory. I realize they arent dodge/Cummins, but they are CP3s.


  9. Top Of Page | #8
    TexNeck's Avatar

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    Re: knock or miss on take off

    Quote Originally Posted by lovemydiesels View Post
    Teaneck- thank you, that seems pretty logical and I suppose something could have entered the system durong install. If I'm already buying parts, should I just get an arson 3 kit to supply my injectors for effectively? Could that be part of my problem? Polaraco- Thank you for the tip, that was something I planned on adding to my setup permanently anyway. The only part I'm not so sure about is I know there is decent pressure becuase i did a bucket test b4 and after my draw straw to dump. I also removed and cleaned the fuel tank. I thought it had a loose fill or vent hose so I pulled it. To my surprise it had a little metal tab siliconed to the top of the tank. I removed it realized that there was melted holes along the top of it. It's directly under the gooseneck hitch in My CM flatbed. Those ding dongs must have had a new welder that didnt cover the tank for spatter and blow outs. So after all of that i would think the dump would stay pretty clean. Also both of my duramax trucks didnt come with a lift pump at all from the factory. I realize they arent dodge/Cummins, but they are CP3s.
    Depening on power goals for arson kit. Factory CP3 with Fass and good tuning will take you in the 650-700 hp range

    2013 Ram 2500
    John 3:16 - Philippians 4:13

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  10. Top Of Page | #9
    Basic Member lovemydiesels's Avatar

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    Re: knock or miss on take off

    bought a new bosch FCA from Glacier Diesel. All my woes are gone. Thx for the pointers.


  11. Top Of Page | #10
    TexNeck's Avatar

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    Re: knock or miss on take off

    Quote Originally Posted by lovemydiesels View Post
    bought a new bosch FCA from Glacier Diesel. All my woes are gone. Thx for the pointers.

    Glad that fixed it! Thanks for the update - hopefully this will help someone else down the road. Enjoy the truck!

    2013 Ram 2500
    John 3:16 - Philippians 4:13

    See what we are up to on:
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    Or Email me at:
    mike@ddpmotorsports.com
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