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Thread: diesel engine revving

  1. #1
    Member steelguy's Avatar
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    Question diesel engine revving

    I don't have a clue why my diesel engine runs great for 6-8 minutes, and then revs up for 40 seconds, then smooths out to normal rpm's. Unfortunately, my tach does not work, but it's hard not to hear it whining. My guess is it has something to do with the fuel, water or dirt, or any one of the three filters is flowed. I am replacing all 3, just in case.

    Anyone have any thoughts?

  2. #2

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    Best first move is replacing those filters as you say you are going to do.
    If you still have issues with it after-wards I'll help you out. Also post which manufacture engine it is and whether it is DI (doubtful) or mechanical pump inj.(likely).

    Another thing, have you struck bottom or propped anything lately ? Could it be the prop hub is spun and briefyl catches then spins ?
    Is the outdrive direct drive ?

  3. #3
    Member steelguy's Avatar
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    Default 338wm

    Perkins straight 6, injection. I have not struck anything, or propped, but good thought. I last used my boat in May, and it ran like a champ, just purred the whole one week trip. Had a mechanic at that time replace the two fuel filters, but now just found a third at the front of the engine. So, my plan is to replace all 3 new. Did have the lower rudder bearing replaced just last week, but doubt this is related.
    thanks 338WM for your thoughts.

  4. #4
    Sponsor potbuilder's Avatar
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    injector/injector pump problems???

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  5. #5
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    Default Diesel Engine Revving

    A great source of info for anyone with a diesel is Boatdiesel.com. They charge for full access ($25/yr I think) but well worth it. You can browse recent posts to check it out for free but you need to subscribe for archived stuff and to post. Go into the Diesel Forums page and there's a forum for the Perkins 6.354 series if that's the one you have. You'll likley find something there to narrow down your problem.

    Good luck!

  6. #6
    Member steelguy's Avatar
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    Default thanks Fish Witch

    I will check your lead out. Love to get an engine manual, that would really help.

  7. #7

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    Did you get the filters changed out and give it a go ?


    Has the air filter been changed, does it smoke excessively?If smoking, what color is the smoke?

    How many hours on the engine?

    If all the above is good and hours are within normal limits, the most likely cause is a worn/faulty injection pump.

  8. #8
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    Default

    Sounds like sucking air somewhere in the fuel line or injectors.

    On the engine you can take wd-40 or starting fluid to see if it is sucking air.

  9. #9
    Member steelguy's Avatar
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    Thumbs up 338WM nailed it!

    So, changed the filters and the following day the engine would not start at all. After 5-1/2 hours of taking off the various fuel lines and checking flow, then temporarily get fuel through the Dickensin stove pump, decided to take the injector fuel pump off to get a part number assuming it was a pump problem. Then, decided to see what the inside looked like and what made it work. Sure enough, one of the valves had come apart. The diaphram looked fine. Managed to put the parts back in place, reinstall the pump and the engine started right up. And, it has been running beautifully since! Purring like a kitten and the rebuilt, 4 year engine with 375 hours it has.

    Thanks to everyone for your guesses and I am sure glad it is fixed. In the meantime, I am planning on ordering a new pump and will install that first chance I get.

  10. #10

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    Excellent, glad you got it sorted out .

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