Anyone With a DD15 and boost gauge. I need to verify something.

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by LoneRanger, Dec 8, 2021.

  1. LoneRanger

    LoneRanger Road Train Member

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    If anyone has a 2013 or close to a 2013 DD15 with a boost gauge, please help me verify something.

    lately I’ve been getting a drag on the drive train and I have gone through the hole truck and nothing should be holding it back going down hill. It feels like the engine brake is coming on.



    I noticed that when I let off on the hammer I’m still showing boost, something that didn’t happen before. I remember this wasn’t the case. When I’m coasting there was zero boost and now I have constant boost when in gear. Am I remembering it wrong? Is my brain playing tricks on me and this was never the case?

    if you can going downhill or flat land and your coasting, do you have boost?

    I’m thinking maybe just maybe my DPF filters are dirty, creating back pressure, which creates boost thus causing mpg to go down and engine brake effect without having my engine brakes actually on.
     
    Last edited: Dec 8, 2021
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  3. LoneRanger

    LoneRanger Road Train Member

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  4. gentleroger

    gentleroger Road Train Member

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    It's been a couple years since I had a boost gauge, but I seem to remember it always showed at least something, even when coasting.

    It's a good question and I'm interested in a real answer.
     
  5. Don379

    Don379 Medium Load Member

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    Yes if you are off the throttle and just coasting down hill in gear at let’s say 1500 rpm you will get a little boost. Typically around 2-3 psi. With the jakes off. Jakes on full, you will get a ton of boost of course.
     
  6. LoneRanger

    LoneRanger Road Train Member

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    Im looking at it I’m around 7-9psi and that’s what has me worried because I usually saw the needle near zero not 10 psi. Leading me to believe it’s time to either clean the DPF filter or replace it.

    learning as I go so not sure when the DPF filters need to be replaced. At what mileage does regeneration not help anymore?
     
  7. Don379

    Don379 Medium Load Member

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    well if its any consolsation, my truck is a preemission cat with straight pipes and zero restriction and i get the 2-3 pounds boost with jakes off
     
  8. lester

    lester Road Train Member

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    Where's all the smart people at?!?

    I don't believe a plugged DPF would make you show boost while coasting. Boost pressure is really just a measure of restriction. But not on the exhaust side but the intake side. If your exhaust system was plugged it would create back pressure on the exhaust side of the turbo which is what drives the turbo. If the turbo isn't able to spool up properly it won't create boost properly. Long story short I don't think that's your problem. And if you dpf was plugged it would be doggy and probably throwing codes
     
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  9. lester

    lester Road Train Member

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    Could just be a bad sensor
     
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  10. Varga

    Varga Bobtail Member

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    Possible egr flap is leaking?
     
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  11. LoneRanger

    LoneRanger Road Train Member

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    but the exhaust side drives the intake side. You need back pressure to drive the turbo to build boost.

    that’s how I understand it.

    also a week ago I got two box conversion errors but I cleared them and did parked regen and it’s been good so far. Although the DPF might be clean enough to not throw codes in thinking maybe it’s getting up there with the age of the truck and not sure when or if they have been replaced. So I’m going to take it apart and see what’s what.
     
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