RPM gauge needle jumping a little in 97 Freightline classic

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Tomek373, Jan 21, 2022.

  1. Tomek373

    Tomek373 Bobtail Member

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    Mar 12, 2021
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    Hello I got 1997 Freightliner classic with 12.7 Detroit and I realized my rpm gauge jumps… it’s a very small movement around 2 millimeters but I still notice it.. is that normal or could there be problems cooking slowly ? It does it both at idle ( unless I bump it up to 900 rpm then it’s steady) and when driving
     
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  3. Kalaramna

    Kalaramna Bobtail Member

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    Jan 21, 2022
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    That’s called surging. Happens because of fuel quantity valve. Not to worry it won’t damage your engine
     
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  4. Slowpoke KW

    Slowpoke KW Road Train Member

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    Dec 7, 2015
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    Could just be the tachometer itself
     
  5. BRD TRANSPORT

    BRD TRANSPORT Light Load Member

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    Jul 6, 2018
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    Hapoend to me still dose.
    New sent u it, yoke I 8versal and Guage from peterbilt.
    Don't sweat details buddu.
     
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