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A25c won't accelerate

Discussion in 'Shop Talk' started by Dakotab19, Jun 10, 2019.

  1. Dakotab19

    Dakotab19 Active Member

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    Hi all new to the forum here and looking for info on an A25C. The problem I'm having is that when you put the truck in gear it won't really rev up and go anywhere. If you just move it around at idle it will move fine, but if you try to accelerate it just bogs the motor down and has no power.
    The Motor was rebuilt when we got the truck and seems to run good, other than revieg up a bit slow from idle. This kind of leads me to believe it's something with the trans, like possibly the retarder being stuck on (if that's possible)
    I don't know if anyone here has any experience with this situation, but even some direction as to a possible cause would be helpful.
     
  2. funwithfuel

    funwithfuel Senior Member

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    Got fuel, how bout boost?
     
  3. thepumpguysc

    thepumpguysc Senior Member

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    What does in do in Neutral.. rev normal or bog.?? THAT'LL tell u if u have a fuel or trans problem..
    IF it revs normal, chances are its trans.. IF it bogs & is slow to accelerate its fuel..
     
  4. Dakotab19

    Dakotab19 Active Member

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    Seems to be getting great fuel pressure haven't checked for boost yet. Is it possible for the exhaust retarder to get stuck closed on these?
     
  5. Dakotab19

    Dakotab19 Active Member

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    In neutral it revs up but from idle it's slow if you rev it in stages it acts normal. I didn't know if that was normal for these motors or if there was a problem, because other than slow reving from idle it seems to run really good, and it starts really easy.
     
  6. thepumpguysc

    thepumpguysc Senior Member

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    Check the over-flow valve on the inj. pump.. they come loose internally all the time.
    Take off the return line banjo bolt & w/ a screwdriver, reach in to the center of the ofl vlv & see if the screw is loose or tight.. IF its tight, leave it alone..
     
  7. Vetech63

    Vetech63 Senior Member

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    What engine is it?
     
  8. funwithfuel

    funwithfuel Senior Member

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    Does it sound like the retarder is stuck on? It's a very distinct sound.
    Has it been like this since rebuilt? Are any of your pumps getting hot?
     
  9. Dakotab19

    Dakotab19 Active Member

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    It doesn't have the distinct whine of an exhaust brake, but I didnt know how these systems would sound.
    I believe it has been this way since the rebuild, but I'm unsure how it acted before.
    When you say pumps do you mean the hydraulic pumps on the trans?
     
  10. Dakotab19

    Dakotab19 Active Member

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    The engine is a Volvo TD73KCE
     
  11. funwithfuel

    funwithfuel Senior Member

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    Yes, if the pumps are loading by a false load sense signal it'll bog the engine. The engine should be able to power through with sufficient fuel n boost. Now if you're hearing a loud rushing noise as opposed to a loud hissing noise, you may be looking for a ruptured boost hose joint to or from the cooler. What kind of smoke you seeing?
     
  12. funwithfuel

    funwithfuel Senior Member

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    By your description, I'm leaning toward retarded injection timing
     
  13. Dakotab19

    Dakotab19 Active Member

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    I am not really getting any smoke it will just puff out a little light grey smoke occasionally.
     
  14. Dakotab19

    Dakotab19 Active Member

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    I checked the valve and it was tight any other suggestions?
     
  15. funwithfuel

    funwithfuel Senior Member

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    Fuel water separator bowl tight?
     
  16. Dakotab19

    Dakotab19 Active Member

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    With retarded timing would it still start good?
     
  17. Dakotab19

    Dakotab19 Active Member

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    Yeah its tight and looked clean.
    Do these engines have an aneroid adjustment, now that I've been thinking about it isn't it a little wierd I'm not getting any smoke at all?
     
  18. funwithfuel

    funwithfuel Senior Member

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    Yes, low fuel pressure = white smoke, low boost = black smoke. Little whisp of grey usually indicates ok.
    Does the engine sound like its laboring to climb up in rpm? If not, I'd see what I could do about confirming pump timing.
     
  19. Dakotab19

    Dakotab19 Active Member

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    It does seem to labor a bit when climbing past 1500 rpm, but not a ton.
    What's the best way to confirm timing on these motors?
     
  20. funwithfuel

    funwithfuel Senior Member

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    IIRC timing window on flywheel housing . Take an 8mm grind a point onto it and screw into 3rd hole. Open pointer cover on pump. I do not know what spec is. It may be on engine ID tag. When pointer is centered in window, timing should point at desired degrees