Maxxforce 13 boost pressure issue

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by tipto3, Jan 18, 2025.

  1. tipto3

    tipto3 Bobtail Member

    9
    2
    Sep 6, 2021
    saratoga california
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    Let me say I know these engines have a bad rep..but I will stand here today and tell you this is my first issue with this truck and it's been the best truck I've owned so far ...just had to put that out there even though it's only 500k miles it hasn't had a single issue ...until now
    So the problem now I will keep it short for you..truck builds boost about 40psi and then instantly drops off to 0 and bounces right back up to 30ish psi (bobtail) I have no codes and no other issues but I feel the loss of power ..it does have the updated acv but it's been on the truck since factory year is 2014...this issue happened every time and sometimes it will only hit 30 psi ...pinched off the waste gate ..no change checked for leaks ...nothing keep in mind it is hitting 40psi just drops as soon as then comes up 10psi lower I can't figure it out. Any help would be appreciated my next guess was air control valve but we know they are expensive and I don't want to throw parts at it.
     
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  3. Heavyd

    Heavyd Road Train Member

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    Feb 4, 2009
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    The manual does say the valve inside the turbo can be manually pushed opened by the boost pressure as a fail safe in case the ACV or actuator fails. I have never come across this, but I wonder if the return spring is weak or broken in the actuator making the push rod have reduced closing pressure on it and boost pressure itself is pushing open the waste gate valve to cause the boost dump?
     
  4. tipto3

    tipto3 Bobtail Member

    9
    2
    Sep 6, 2021
    saratoga california
    0
    So my initial thought was...wastegste...let's pinch it ...no progress....what else controls boost....or should I say holds the pressure...charge piping correct along with the manifold and cac...so with it building as high as it does would t indicate a leak I don't assume..so with that said then what's left? Air control valve? I'm pretty stomped ..will try to upload the short clip
     
  5. Heavyd

    Heavyd Road Train Member

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    Feb 4, 2009
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    I am thinking the valve inside the turbo is getting pushed open. When you pinch the line at the actuator, air comes from the ACV, not the intake manifold. Once you pinch the line, the actuator is no longer able to dump boost. If you had a major boost leak, it would make loud pop or squeal noise, so I don't think that is it either. If the flap valve is getting pushed open inside the turbo, you need to hold it closed. Force the wastegate rod from moving by jamming it with vice grips or something to see if the boost drops or not. If it does, then something external is doing it and we can look again for a boost leak. If it holds pressure and boost, then I think the return spring in the actuator is weak or broken.
     
    little cat 500 Thanks this.
  6. tipto3

    tipto3 Bobtail Member

    9
    2
    Sep 6, 2021
    saratoga california
    0
    Forgot to mention on rare occasions theres a sudden increase in power as if there is no loss of boost but this rarely happens I mean maybe once a month for a couple of gears then it goes away for that would maybe rule out a boost leak so I will try what you suggest...if that doesn't work then I'm very interested on how this avc works.....I will report back tommorow thanks a lot
     
    Heavyd Thanks this.
  7. tipto3

    tipto3 Bobtail Member

    9
    2
    Sep 6, 2021
    saratoga california
    0
    Ok so I decided to just plug the waste gate line instead of pinch it I guess it wasn't pinching correctly due to the type of hose...anyway did that the boost pressure went up to about 40 but the acceleration is now noticeably slower not by much feels like I'm only getting -75% throttle that's the only issue now fp is in line with desired and boost pressure is building ...it was accelerating better but no boost now more boost slower acceleration....I don't know what to do from here ...engine brake also seems louder at times than others.....keep in mind I'm bobtailing I'm kind of nervous to put a load on it now but don't know what else to check ...acv? I did unhook it just to see what it drives like an it almost feels the same
     
  8. tipto3

    tipto3 Bobtail Member

    9
    2
    Sep 6, 2021
    saratoga california
    0
    New update..tc1top reads 0 seemingly at all times and engine throttle position remains at 0 ....truck is deleted for the last 4 years im just wondering is this an issue to check into I know nothing about tc1 senor...also turbo outlet is at 0 ....even when the truck is making boost....that's all I can find that's reading 0 but fuel pressures are perfect ....just a little low on power missing a little push ...it starts off good but seems to die out around 1400 but building correct boost....just waiting on replies ...thank you...
     
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