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Thread: bobcat 773 help

  1. #1
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    bobcat 773 help

    My bobcat 773 stalls and seems to get air in the fuel lines. Im am not a diesel mechanic so anyone who can tell me where to look for this problem would be a big help. Someone told me that alot of bobcats develop a bad grommet in the fuel tank and that can cause this. Is this hard to fix?

  2. #2
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    Wadman,I'm not familiar with the 773,so the "grommet" thing may be the problem.

    I had a similiar problem that slowly got worse with my Bobcat.After sitting a few days it would fire right up,but then die after about 2 seconds.Then it was VERY hard to get restarted again.If it had just been running awhile,it would fire right up,and wouldn't stall at all.As time went on it was harder and harder to get started cold.It acted like air in the lines,but it turned out to be the injection pump.It was just plain worn out.There was too much clearance between the close fitting parts.

    Hopefully that is not your problem,the pumps are expensive.If you truly have air in your lines then it probly isn't the problem.I've a Isuzu 2AA1 diesel in mine.In mine the fuel is drawn up the fuel line,out of the top of the tank,it then goes into a seperate mechanical lift pump,then it's pushed through the filter assembly,and finally into the injection pump.Mine doesn't have a grommet in the fuel tank,other than the one sealing the fuel/fuel return lines, where they enter the tank(and they couldn't cause a starting problem).I'm not sure why yours would have a grommet inside the tank either,but it may have one regardless.

    If fuel level affects this problem,then it probly is inside the fuel tank.A fuel line leak between the tank and engine would most likely show up with diesel fuel leaking out also.Without any signs of that,I'd next look for anything that could restrict fuel flow(pinched line,plugged filter)or possibly a defective fuel pump(if it has a seperate one).My lift pump has a lever mounted to it too manually operate it.If air is in it,it feels mushy when moved,and firm when the system hasn't any air.

    I know it's not specific info for your model,but maybe it'll help anyway.

    Good luck!!

  3. #3
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    Check your fuel primer bulb. The nice thing about bobcat when you run out of fuel its easy to reprime. Only problem is the primer bulb can crack at the pipe clamps on the fuel line. Which lets in a little air.

    There is a little knob on the side of the injector pump. Turn it so it is open. Then squeeze the the primer bulb if you hear air flowing thur the injector fuel lines and in the return line. Then you know its the primer bulb or the fuel line.
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  4. #4
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    The best thing to do imho to check for air getting in your fuel system is to remove the fuel return line and submerge the end of it into a pail of fuel. Start the engine. If you have a air leak the bubbles coming out of the return line will be quite noticable. Try moving your rubber lines, etc to see if it makes the bubbles size or amount change.
    Ken

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    Air in fuel - Bobcat 753

    I have a Bobcat 753, approx 2000 hours, and a similar problem with getting air in the fuel system. The machine runs like a new one on the first 1.5 to 2 gallons. after that, it's game over. I have replaced the primer bulb and all fuel hoses downstream of the bulb.

    Top off the tank, squeeze the buld and prime the fuel filter, crack open the bleeder, hit the key, and back in action for another 2 gallons.

    The problem remains after the new hoses and bulb, so I suspect as in one of the previous posts there must be some sort of pickup tube in the tank that is cracked...or maybe its that one last factory hose from the bulb to the tank.

    Has anyone got into one of these tanks before to know if there is a pickup tube?

    Anyone out there have a fuel system schematic they could pdf my way?

    I'll be tearing into my machine this weekend...if I stumble across anything I will revise my post to detail what I have found.

    Thanks,

    Mike

  6. #6
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    Smile Problem Solved - Air in Fuel Bobcat 75

    Per my post last week, upon inspection I found that the fuel is drawn from the top of the tank via a dip tube. Factory length is 9 inches plus a screen.

    My machine's dip tube had rotted off at 2 inches (which evidently equals 2 gallons). New hose, screen, and grommet came to less than $25 including shipping.

    Back in action.

  7. #7
    Administrator digger242j's Avatar
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    First, Mike, welcome to the forums! (It doesn't look like anybody else bothered to do that. I think Countryboy is chairman of the welcoming commitee. I'll have to have a talk with him...)

    Thanks for the update on your machine. Even though nobody else apparently had the answer to your question, now that you've found it on your own and shared it, we all have that answer.

  8. #8
    Senior Member Countryboy's Avatar
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    Quote Originally Posted by digger242j View Post
    First, Mike, welcome to the forums! (It doesn't look like anybody else bothered to do that. I think Countryboy is chairman of the welcoming commitee. I'll have to have a talk with him...)

    Thanks for the update on your machine. Even though nobody else apparently had the answer to your question, now that you've found it on your own and shared it, we all have that answer.
    Aww shucks, my bad Arcfiddler........Welcome to HEF!

    And thanks for ruining the surprise DIGGER!!! Now he knows that he is "Welcome" and the party ain't till tomorrow.

  9. #9
    Senior Member hvy 1ton's Avatar
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    I have had that problem with diesel equipment several times. Last year with my JD front mower. I had rotted pick-ups in both tanks. They broke off around 3 in so every time i went on a side hill no more lawn mowing. The downhill tank would work and the uphill wouldn't it, so took awhile to figure out.
    I'm just glad I was sure it wasn't the injection pump.

  10. #10
    Super Moderator CM1995's Avatar
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    I had the same problem with an 853 bobcat. First time it was a clogged screen in the fuel tank - made the engine run sluggish but it ran. Second time it was the pick up tube, it had rotted off.

  11. #11
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    Where did you find access to the fuel line into the fuel tank in order to replace the little tube? I can't find any access when I raise the cab, nor from the rear or sides. ???

  12. #12
    Senior Member Countryboy's Avatar
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    Welcome to Heavy Equipment Forums mudflapmax!

  13. #13
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    On my machine, once I raised the cab, I had to nearly lay on my stomach with my feet hanging out over the bucket. Directly in the center of the machine there is some sort of red gizmo...it might be black until you do some cleaning in there. Just behind that, slightly under the engine you should see the black poly fuel tank. I believe mine had two rubber grommets with 90 degree push in fittings. The lines ( one feed, one return)come off the top of the tank and run rearward under the engine. I would reccommend putting your machine out side, roll the cab, and give her a good cleaning with some engine degreaser prior to popping out the grommets. I used a flat blade screw driver and a steady hand to pop the grommets out...the dip tube / screen will follow.

    Its been awhile since I did this, so the description above may be off a bit, but should be close enough to get you looking in the right place.

    Headed out of town in a minute and in a hurry...otherwise I would e-mail you a photo...my apologies in advance.

    Good Luck!

  14. #14
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    Quote Originally Posted by wadman View Post
    My bobcat 773 stalls and seems to get air in the fuel lines. Im am not a diesel mechanic so anyone who can tell me where to look for this problem would be a big help. Someone told me that alot of bobcats develop a bad grommet in the fuel tank and that can cause this. Is this hard to fix?
    I have the same problem. Did you have to remove the engine to access and replace the grommet and filler tube at the tank? Or is there another way to get to it?

  15. #15
    Senior Member Countryboy's Avatar
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    Welcome to Heavy Equipment Forums jnstrawn!

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