Series 60 Hard start when WARM

Discussion in 'Freightliner Forum' started by a2myers, Jan 10, 2021.

  1. a2myers

    a2myers Bobtail Member

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    Mar 2, 2018
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    I’ve got a factory powered Columbia with a 14L pre-emission Series 60, 480k on it.
    It starts fine when cold, but stumbles on start when already warm.... sometimes cranks longer and sputters worse than other times and even starts normally sometimes. Idles and runs great, good power and fuel mileage has been consistently good.
    Been like this for a few years, not bad enough to worry about and throw money at, but seems to have gotten a little worse the last few months. Suggestions?
     
    Last edited: Jan 10, 2021
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  3. Kenworth040

    Kenworth040 Bobtail Member

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    Jan 10, 2021
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    Try checking your crank sensor or cam sensor i believe the detroits have 2 crank sensors on the front of the block have those checked out thats what it sounds like to me good luck
     
    a2myers Thanks this.
  4. Hulld

    Hulld Road Train Member

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    Oct 19, 2015
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    Check valve on the back of the head maybe?
    Or possibly the check valve in the Davco filter if it has
    one ?
     
    magoo68 Thanks this.
  5. a2myers

    a2myers Bobtail Member

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    Mar 2, 2018
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    Possibly, but I would think those check valves would be more of an issue after it sits awhile and slowly leaks back? It’s odd to me that it starts hard once the engine is warm and starts fine when cold. For example, it sat for a week and started right up, let it go at high idle for about 45 min and get up to temp, shut it off for about 45 min, and then started hard after that.
    Not sure if the sensors mentioned above would be engine temp dependent? Or if the ecm isn’t controlling the fuel properly on hot starts? Or something physical/mechanical like injector o-rings?
     
  6. mdbell26

    mdbell26 Bobtail Member

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    Aug 11, 2017
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    Injector o-rings is a decent guess.
    Being a factory “pre” 14 you have n2 injectors. They are notorious for leaking. I would think heat might make it worse. Fuel in filter normal color? Fuel in oil? Response times good at operating temp? If everything checks out it could be a small cylinder head crack.
     
    a2myers Thanks this.
  7. a2myers

    a2myers Bobtail Member

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    Mar 2, 2018
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    Zero fuel in the oil (I regularly sample), so I know it’s not injector leakdown.
    The Davao filter had been turning black prematurely, which started late in the summer and also coincided with higher/quicker soot accumulation in the oil than normal. Fuel filter discoloration was a new one, but had similar high soot load in the oil the previous summer (I ran biocide, injector cleaner, and fuel tank cleaner and it corrected the problem). I had thought that might be attributable to the hot weather, the Detroit’s characteristic of getting the fuel hot, and asphaltene. So did the same additive routine this time, but truck has been parked since then (getting out of the business, trying to get it sold).
    Did not notice any performance/response issues and fuel economy was maintaining the normal range.
     
  8. habfleet

    habfleet Light Load Member

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    Feb 5, 2012
    elwood nj
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    If your injectors or O rings are going you will begin to get oil in the fuel. that could be why Davco filter is turning black
     
    Bean Jr. Thanks this.
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