briggs/diahatsu diesel loss of power under load

Discussion in 'Mechanic and Repair' started by gilbert93, Apr 7, 2007.

  1. gilbert93

    gilbert93 LawnSite Member
    Messages: 3

    anybody with experience on diahatsu/briggs diesel on scag sabre tooth tiger?
    with mower engaged, machine bogs downs in all but the shortest grass, or mowing on any incline. have replaced fuel filter, belt and deck spring (broke 2 coils off the end), blades sharp and straight, all greasing done religiously. all spindles turn freely, gearbox is ok as well. unit only has 269 hours - 3 mowing seasons. runs/sounds fine without mower engaged. does not smoke, or run rough, just slows down in grass it normally destroys at top speed. it's in the shop now, but dealer is not sure what is the cause - they have more than 30 of these out in the field and have not seen this problem before.
  2. tomo

    tomo LawnSite Senior Member
    Messages: 660

    1 compression test
    2 if turbo equiped check pressure
    3 check fuel line 4 blockage
    4 check throottle cable adjust
    5 check valve clearance
    6 check pump timing

    if all checks ok send pump and injectors to be o/hauled

  3. twj721

    twj721 LawnSite Senior Member
    Messages: 619

    have you checked the air filter to see if it is plugged up ?
  4. TLS

    TLS LawnSite Fanatic
    Messages: 7,943

    Did you get some bad or dirty fuel?

    Drain tanks and replace fuel filter again.

    It doesn't sound mechanical as far as the deck goes as you said everything on the deck seems OK.

    Did you run out of fuel lately and maybe you still have air in the system?
  5. gilbert93

    gilbert93 LawnSite Member
    Messages: 3

    i just got back from the dealer and he said the throttle cable had slipped and it was running at 3200 rpm - about 10% below where it should be. the air filter was dirty - even though the red indicator never came on. thank you for all your responses, they have all been helpful.
  6. gilbert93

    gilbert93 LawnSite Member
    Messages: 3

    i got my scag back from the shop last week and it mowed fine until fri when we filled it back up and then it began bogging down under load again. the throttle cable was still ok, so i drained the tank and went to a filling station and brought back 10 gal of fresh diesel. put it in and it ran correctly again. the "bad" diesel is in an above ground tank (225 gal) that i got last summer.
    it was filled in august of last year and used without problem until the first use this year. the tank has a new hand pump and filter that we installed when we got the tank. the tank is capped tight and the fuel pickup for the pump is approx 8 - 10" above the bottom of the tank. the fuel company that sold us the fuel said they have no complaints about any diesel that they have sold; they sell quite a bit as they are a farm supplier. does anyone have any suggestions? if additives are needed, which do you recommend? anyone know of a testing laboratory that could be consulted?


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