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Poor MPG after replacing head

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Markovkus, Feb 22, 2018.

  1. Feb 22, 2018 #1
    Markovkus

    Markovkus Bobtail Member

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    Dec 2, 2017
    0
    How is everybody doing here?
    Trying to figure out why my fuel mileage went down after replacing head on '09 Volvo D13, 820K, manual. The head was replaced 12K miles ago after I completely lost compression on 6th cyl, the exhaust valve seat was the reason. Along with new head did replace injectors, cups and wire harness. The cam and rockers were good.
    After the job was done I experienced a noticeable drop in MPG. Right before breakdown I had 7.2-7.4mpg pulling a 30.000 at 65mph. Now I can barely making 6 under same load, speed and terrain. Slight vibration appeared at low rpms when accelerating. Almost disappeares after driving few hundred miles. Truck pulls pretty much the same as before. MPG shown is both the same from ECM and my own pump to pump calculations ( did pay attention to night idling as well).
    Really frustrated because expected some gain in power plus AT LEAST SAME fuel consumption. Especially that compression test was good and truck is not using oil at all...
    May be poor adjustments? Or being paranoic and all that is winter time related?Any ideas?
    Thank you!
     
    Markovkus, Feb 22, 2018
    Markovkus, Feb 22, 2018
    #1
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  3. Feb 22, 2018 #2
    AModelCat

    AModelCat Road Train Member

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    Jul 7, 2015
    Canuckistan
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    Zero Volvo experience but personally I'd have the valve lash checked for proper adjustment (if that's possible on Volvo engines?).

    How's the boost? I'd check and see if maybe they forgot to tighten an intake clamp and you're losing a bit of boost?
     
    AModelCat, Feb 22, 2018
    AModelCat, Feb 22, 2018
    #2
  4. Feb 22, 2018 #3
    Markovkus

    Markovkus Bobtail Member

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    Dec 2, 2017
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    Boost is the same as before. Already pressure tested including intercooler
     
    Markovkus, Feb 22, 2018
    Markovkus, Feb 22, 2018
    #3
  5. Feb 22, 2018 #4
    GrapeApe

    GrapeApe Road Train Member

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    Jan 7, 2013
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    Adjustable? Yes, but not in the sense most of us are used to. It requires changing shim thicknesses. A whole shim kit is expensive. But without it, you need to measure the clearance, and if it needs to be adjusted, measure the shim in it and use thicker thinner one to get it right. When I worked for a fleet that had Volvo's. We had a whole kit and ordered replacement shims to replenish the kit as we used them. Not very economical for 1 truck though, so most people just have a shop equipped to to them do it.
     
    GrapeApe, Feb 22, 2018
    GrapeApe, Feb 22, 2018
    #4
    AModelCat Thanks this.
  7. Feb 22, 2018 #5
    Markovkus

    Markovkus Bobtail Member

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    Dec 2, 2017
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    I remember the guys who did the work on head asked me to bring two shims 3.35 thick
     
    Markovkus, Feb 22, 2018
    Markovkus, Feb 22, 2018
    #5
  8. Feb 22, 2018 #6
    nax

    nax Road Train Member

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    Im watching this thread veeeeeery closely.... like this >.<
     
    nax, Feb 22, 2018
    nax, Feb 22, 2018
    #6
  9. May 2, 2018 #7
    ebill45

    ebill45 Light Load Member

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    Oct 11, 2011
    dalton ga
    0
    Give it 30k miles to break in
     
    ebill45, May 2, 2018
    ebill45, May 2, 2018
    #7
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