14.0 detroit 515 help, 4.1mpg is killing me

Discussion in 'Trucks [ Eighteen Wheelers ]' started by jayz8886, Nov 2, 2009.

  1. jayz8886

    jayz8886 Bobtail Member

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    The truck is a 05' Xl Freightliner, specs are 480k miles, 3.55, 13 speed .78 over with 22.5 rubber, an a 14.0 515 detroit.

    My driver is complaining of low power and on the best mpg average its getting 4.3. I have it governed to 68 and it hauls a 48' flat.

    I have had it back to the Freightliner shop 2 times and they say that all is good that it driver and not the truck. But he came from my 03' Xl with a 500 detroit set to the 68 mph getting 6 mpg.

    I'm at the point where I will do better parking the truck than dealing with the bad mpg.

    Is anybody else having these issues or have ideas on where to look?
     
    Last edited: Nov 2, 2009
  2. Stroked F550

    Stroked F550 Medium Load Member

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    have you checked for boost leaks?
     
  3. Jim Bob

    Jim Bob Light Load Member

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    Put it on a dyno and go from there. $150 is cheaper than wasting it in fuel.
     
  4. Tank33

    Tank33 Medium Load Member

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    I posted in a similar thread of mine that I have a friend with a Classic and a 14.0L Detroit, his fuel mileage is horrid. He is running 3:70 or 3:90 rear ends, cant remember, 13 speed, 22.5 rubber. He drives between 100 and 110 KM/H, pulls heavy one way, and very light the other, and his fuel mileage is horrid, usually in the 4's.

    Freightliner says it is working right.

    My suggestion is, take it to Detroit, not Freightliner. Freightliner mechanics focus on Freightliner trucks. Detroit mechanics specialize in Detroit engines, take it to them, let them update the software and check the turbo, and check the air-to-air. Pressure test for leaks.
     
  5. jayz8886

    jayz8886 Bobtail Member

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    Yes is shows to be fine on a leak down test. I have went over all the common stuff on it that I am use to doing on Detroit's (filters,leak down,boost).

    This is the first egr engine I have dealt with and just not sure where to go. It shows to be getting 6.5 on the comp but the real numbers only show around 4.1-4.3.

    I don't have the time but I may have to take a few runs in the truck to see how it actually runs. The only seat time I have in it is from bob tailing home from the dealership.
     
  6. Jim Bob

    Jim Bob Light Load Member

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    Is somebody stealing your fuel outta the tank? It happens. That or you might have a diesel leak.
     
  7. jayz8886

    jayz8886 Bobtail Member

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    Its possible, but have no evidence to say its leaking or bein stolen.

    I will see about getting it into detroit in the morning to have them look it over.



    Thanks for the help.
     
  8. PaulE

    PaulE Medium Load Member

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    Had a friend spend alot of money and time chasing same problem with an MBE. turned out truck was fine, odometer was running way short. changed tire size when he bought the truck and odometer had not been programmed right.
     
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  9. 550hpW900L

    550hpW900L Road Train Member

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    Sounds like your driver is selling fuel.
     
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  10. stranger

    stranger Road Train Member

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    Was going to say that myself. I've had drivers sell some of mine before.

    According to Detroit specs, a 3.36 rear would be better for fuel mileage since you have a .78 OD and LP 22.5s
     
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