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bobcat 773 down on power/fuel related

Discussion in 'Skid Steers' started by James Clark, Mar 29, 2020.

  1. James Clark

    James Clark Well-Known Member

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    I have a 1999 bobcat 773f series, once my engine is warmed up the rpms drop off under load then even just running around and the unit will hardly run. It will even die sometimes. I've replaced all fuel lines and primer bulb, fuel filter.
    I read one thread that said if i could use the primer bulb to keep the rpms up then i should change the pickup pump, needless to say it didn't solve my issue. I also have installed a clear fuel filter in the fuel line in front of the primer bulb.
    So i think i'm going to hook a gal. jug straight to the primer bulb and see it that makes a difference, if it helps then i can assume that the fuel pick up line is my issue ?
    Any one have any other ideas as to what i should do.
    thanks for any ideas james
     
    Delmer likes this.
  2. DeereJohn

    DeereJohn Active Member

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    Fuel pickups are a common issue

    Mine would run fine full and get progressively worse below 3/4. G series but probably no different.
     
    Delmer likes this.
  3. James Clark

    James Clark Well-Known Member

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    Thx for your suggestion.
     
  4. James Clark

    James Clark Well-Known Member

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    As a follow to my issues with my bobcat, I unhooked the fuel tank from the system and hooked a qt. bottle just in front of the primer bulb and tried to rule out the tank and the lines from it as possible issues for the motor bogging down when it fully warmed up.
    This didn't change a thing as far as the unit still bogged down and died, so at this time i'm out of ideas as to what it could be.
    Does anyone know if the injector pump could cause an issue like this, where it runs fine till warmed up then just falls on its face.
    Thanks again for any input.
     
  5. thepumpguysc

    thepumpguysc Senior Member

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    Does it have the small Kubota 4cyl. engine.?? w/ the small PFR style inj. pump.??
    Why havent u changed the supply pump.??
     
  6. James Clark

    James Clark Well-Known Member

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    If you mean the small pickup pump I’ve changed it. Ibe changed everything but the injectors and the main injector pump so what I wonder is why it runs fine till it warms up then it has the issues I’ve mentioned
    Thx jc
     
  7. James Clark

    James Clark Well-Known Member

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    I cant remember right off what the model of the engine is but it is about 40 h.p so I'm sure it's the small engine.
    I'm Mechanically incline so with that thought i'm not sure how the main pump can run right then have a issue after warming up? but I don't know enough about injectors to be so sure they couldn't have an issue after warming up.
    I appreciate any thoughts thepumpguysc. Thx
     
  8. DeereJohn

    DeereJohn Active Member

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    It really sounds like it’s sucking air or not getting enough fuel. Does this Kubota have a mechanical lift pump? It would be mounted on the side of the block.

    I would recommend trying to isolate the problem. Run a line into a can, to a cheap 12v pump, then straight to the filter mounted on the machine. Pull the return line from the injectors back into the can. This way you know you are forcing fuel into hp pump.

    I assume you have cracked all the lines and have steady flow, and checked for any difference in how it’s running as the injectors are cracked.
     
    rmllarue91 likes this.
  9. willie59

    willie59 Super Moderator

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    Bobcat 773 F series should have a Kubota V2203 engine. You need to make sure the fuel solenoid is pulling the shut down lever fully into the run position and verify the prime bleed screw on the injection pump return line is screwed in fully CW.
     
    rmllarue91 likes this.
  10. bobatack

    bobatack Active Member

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    Have you verified the possibility of water contamination in fuel tank?
     
  11. James Clark

    James Clark Well-Known Member

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    Thx for all of your reply’s, I have changed the lift pump that supplies the main injector pump and I have hooked the system to a qt bottle of diesel at the primer bulb and ruled out both things(water hoses ect) so I can’t believe the injectors or the injector pump would work fine one min then give me an issue of bogging down/lack of RPM’s and or power
     
  12. James Clark

    James Clark Well-Known Member

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    So I’m open to any more ideas as I appreciate any and all suggestions thx
     
  13. thepumpguysc

    thepumpguysc Senior Member

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    THE SHUT OFF SOLENOID GETTING HOT & BREAKING DOWN.. ALLOWING THE PLUNGER TO
    HIT THE PUMP RACK..??
    {Stupid cap lock} Take the solenoid OUT of the picture.. stuff some paper towels into the hole if ur worried about oil splatter & run the pizz outta it..& report back..
     
  14. James Clark

    James Clark Well-Known Member

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    I've now tryed a bottle hooked right to the primer bulb but haven't considered the solenoid as being a possible issue best it runs for a few min then when warmed up the problem of loss of rmp's and power happens
    but i can see where if the coil is breaking down maybe its not holding the shut off fully open and could be my issue.
    Tonight after work i will tie it open and see if that solves my issue so once again thanks to all that are offering ideas
    and i'll post the results of the test
     
  15. willie59

    willie59 Super Moderator

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    As I mentioned previously, make sure that fuel lever (red arrow) is fully in the RUN position while the engine is running, and make sure the bleeder knob (item 1) is fully closed CW. You might consider disconnecting the return hose connected to the bleeder valve and add a piece of hose to the bleeder valve going to a container so you can monitor how much leakage is going through the bleeder valve with engine running. 763F fuel solenoid.png
     
    rmllarue91 likes this.
  16. James Clark

    James Clark Well-Known Member

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    i will try your idea willie as i'v run the machine and checked the shut off valve and it appears to be rock solid as far as not choking the fuel flow down.
    But i haven't tried running the bleeder line back to a bottle to see how much is coming by.
    Should there be some coming by, or none at all?
     
  17. James Clark

    James Clark Well-Known Member

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    Today I’ll test the bleeder valve blow by, but along with that is it possible to have the injectors and or pump go down on performance once the machine is warmed up?
    I struggle with this since there both mechanical in design
    Thx again
     
  18. frg

    frg Member

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    there is 2 spring on the back of the throttle lever on engine that connect the speed liver to the Governor in front case. maybe they became weak. to access them, you must open solenoid, then 4 of 10mm bolt on throttle lever.(exactly on plate that red arrow shows one above picture) then you could see those springs.
     
  19. James Clark

    James Clark Well-Known Member

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    Ok I’ll look thx frog for the help been very hard to figure out
     
  20. willie59

    willie59 Super Moderator

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    I haven't checked that before myself so I don't know, only thinking you mentioned it starts fine then has problems once it warms up, my thought was monitor the return flow from the bleeder valve and see if that flow changes as it warms up.