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955l fuel pump issues

Discussion in 'Track Loaders' started by workshoprat92, Aug 17, 2022.

  1. workshoprat92

    workshoprat92 Senior Member

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    I have a 955L that ran fine when parked. Two weeks later went to start it and it runs for a short amount of time and stalls. Have to let it set a bit and it will fire back up but stalls again. Changed fuel filter and water seperator. No change. Getting good fuel pressure on the gauge. When running you can crack the injector lines at the pump. 1,3 and 4 all have a change in tone and cause a misfire. They spurt a small amount of fuel but nothing extreme. Crack open number 2 and there is no change in tone or rpm. It flows bunches fuel! Not a spurt like a timmed injection but a massive constant flow like an open fuel hose! When it runs it runs like its at high or full throttle and wont idle down till it slows down and dies out. Any ideas?

    Machine specs: 955L
    serial number 85j10889
    Eng serial number 78P31504
    Engine was replaced by wagner equipmrnt in denver back in 8
    Parts book shows fuel pump to be a 6N281 pump group
     
  2. thepumpguysc

    thepumpguysc Senior Member

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    U have a stuck plunger and barrel or a broken spring ON the p&b..
    If your pump has the removable plate that covers the top of the pump.. u can gain access thru there.. BUT.. without the tool to remove the “bonnet” the process is worthless..
     
  3. workshoprat92

    workshoprat92 Senior Member

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    The bonnet being the part at the top of the pump where the injector lines attach? I see it looks like a special tool. Wonder how much one is. I do have a manual and a high degree of mechanical skill and experiance. should be able to do any work myself barring any fuel settings requiring a test bench. Have done bunches of cummins pt pumps and a few rosamasters. Havent had to ever mess with a cat pump but it looks like a scroll type pump and meeters fuel much like a detroit injector?
     
  4. workshoprat92

    workshoprat92 Senior Member

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    Im guessing that with number two pumping fuel like it is, I am thinking that it is leaking fuel pressure internally and not allowing the other injectors to get proper fuel supply? Is this the basic problem?
     
  5. thepumpguysc

    thepumpguysc Senior Member

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    The bonnet tool from cat is right at 30.-35.0. at least here anyway.
     
  6. workshoprat92

    workshoprat92 Senior Member

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    The cat dealer here wants $79 for it. I can get it for less than $20 on the internet!
     
  7. AllDodge

    AllDodge Senior Member

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    If you do the rebuild post the process and pics
     
  8. workshoprat92

    workshoprat92 Senior Member

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    Ok so i got the side cover off the pump. Right away i see i errored in thinking i had a scroll pump as its a sleve metering pump. Bumped the starter over and sure enough number 2 pluger went up and would not come down. The rack that moves the sliding sleeves was also stuck and very hard to move. Took some carb cleaner and douched the inside of the pump. A pretty nast coating of funk came off everything. Appears I have some fuel contamination. I managed to get the rack clean enough and worked it free while spraying with carb cleaner. It is now fingertip touch free. Still working on #2 plunger. May have to bite the bullet and get the tool to take it apart and clean it. Thinking i need to drain the tank. Flush tank and entire fuel system. Go back with clean diesel and treat with some anti fungal!
     
  9. thepumpguysc

    thepumpguysc Senior Member

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    Find out what cat wants for a pump o/h and to take off and put back on... & I’ll take 10%.. lol
    What u don’t wanna do is go tapping on anything with a hammer.
    It’s gonna b best to buy the tool AND a new oring that goes under the bonnet..
    Once u get things free.. u have to TORQUE the bonnet back down..
    Good luck..
     
  10. workshoprat92

    workshoprat92 Senior Member

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    I think I got it! Kept soaking the plunger and little by little it started to move. It was going super slow and id have to wait for it to slip back down. Standing there looking at the spring i thought man this reminds me of briggs and stratton valve springs. Then an idea hit me like a brick! I went over to my tool box and in a lower drawer all the way to the back, covered up and almost forgoten was my briggs and stratton valve spring compressor. I took it over and sure enough i was able to work it in where i could slowly work the plunger back down the back up. After a dozen or so cycles of work it down, clean, lube then work it back up and repeat it got to the point where it would come down on its own! A little more effort and a bunch of carb cleaner it was free as can be. By this time its dark enough my old man eyes are useless. So i sprayed it with lube and put the cover back on. Tommorow i should be able to clean it out, put new gasket on and put cover back on. Prime it up and fire it! Fairly confident i got er fixed. While i got all the covers off im gona go ahead and change the fan belts, thermostat, oil and filter and wash out the radiator. Been wanting to do that for a while now so its a good time to get it done!
     
    James Sorochan likes this.
  11. workshoprat92

    workshoprat92 Senior Member

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    Thepumpguysc you were spot on about the stuck plunger! Thank you!
     
  12. Bluox

    Bluox Senior Member

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    Before you start it take the air system apart so you can block air to motor with a plate or plywood in case you have a runaway, SOP Cat.
    Bad Bob
     
  13. thepumpguysc

    thepumpguysc Senior Member

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    I slept at a Holiday Inn last night..
     
    showrguy likes this.