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Happy New 955L Owner With Questions

Discussion in 'Track Loaders (NOT CTL)' started by leadfarmer, Dec 17, 2019.

  1. leadfarmer

    leadfarmer Well-Known Member

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    I didnt get a chance to work on it this weekend. Hopefully this evening I will.

    If the lift pump died, how could I tell?

    The fuel pressure gauge is working, and even when I’m running out of fuel it says I still have good pressure which is odd.
     
  2. Nige

    Nige Senior Member

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    Try the easy stuff first. Look at the fuel cap.
     
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  3. 361brock

    361brock Well-Known Member

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    You might not notice a weak lift pump with a full fuel tank, but when the level drops below the height of the main injection pump (head pressure) the machine will crap out. You will then try pumping the primer, refill the filter and it will run a bit and crap out again. That is one way to tell.
     
  4. kshansen

    kshansen Senior Member

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    Yep may be cheap and lazy but I always checked the free stuff and the easy stuff first!
     
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  5. charles walton

    charles walton Senior Member

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    I don't know which fuel system you're loader has but a few years ago I had a 955L 13x and it was acting like yours and it ended up needing the injector pump rebuilt. I have a guy down home that's retired from CAT and he was the fuel pump man for years and he is still doing them at home and does it VERY reasonable compared to the dealership. The rebuild fixed mine.
     
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  6. leadfarmer

    leadfarmer Well-Known Member

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    What caused your IP to start acting up? Could you send me the guys phone number so I could pick his brain?

    Tonight’s summary:

    Checked the fuel tank cap, vent hole was clear, filter material long gone.

    Disconnected the line front the tank to the filter and blew air through it again.

    Removed filter again, fuel looked good in it and it was full. Blew air through both sides of filter housing.

    Removed line from filter to injection pump and blew air through it and cleaned it.

    Confirmed good fuel flow to filter. When I put the filter on I had to use the hand priming pump to get fuel to keep flowing through the filter housing outlet, otherwise it wouldn’t naturally flow through. Not even a drip. But with the oulet line removed each pump of the hand primer gave a good blast. Any concern there with it not flowing through the filter housing once the filter was primed?

    So after all that it is still doing the same thing. I would run it a few minutes and it would bog down. I did remove the fuel cap just to check if that was it.

    The fuel pressure gauge never drops except when I throttle down to very low idle or shut it off.

    when I go to reprime the system after a short shut down I get air pressure, and then the fuel at first looks foamy with small bubbles until it clears.

    when it bogged down I idled down and the idle sounded rough. It sounds good when I rev up but something just sounds off in the idle. I will try to post some video but I know engine sounds never sound the same in phone videos. But anyways, after I let it idle awhile it starts to sound good and then I can run it hard for a few minutes again, then it starts bogging, like I gave the fuel system a chance to catch up.

    Maybe I’m a goober, but do I need to bleed at the injectors? With it running so good for the 10 or so minutes after re-priming I figured that doesnt need done.

    All this seemingly because I let it run out of fuel once!!! Gah!!!

    Could something be going on with a pressure relief valve?
     
    Last edited: Jul 26, 2022
  7. sawmilleng

    sawmilleng Well-Known Member

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    I'm shotgunning some suggestions here because I am not familiar with your specific engine/fuel line/filter injection pump layout, other than what I could see on photos on this thread.

    Have you checked that there is fuel pressure from the filter to the injection pump when it is running strong? I'm kind of wondering if the fuel pressure gauge is wonky. If you crack the fuel supply fitting where the line enters the injection pump you may be getting air or a mixture of air and fuel rather than all fuel. If you are getting lots of fuel when running strong, try the same test when it is crapping out.

    Also--this is a long shot...are you screwing down the manual fuel pump handle after pumping? It seems to me that the manual pump piston must not move when things are running or prime disappears.

    No fuel running out of the line to the injector pump with the motor off sounds a bit suspect, too...although the ups and downs of the line may be causing this. Maybe try putting a little compressed air on the tank vent to see if you can convince the fuel to move all the way through?

    Does fuel run by gravity to the fuel pump? I found that out the hard way on my stone age 2U D8 because the pump was worn enough that it would not pick up the prime from the tank until there was enough fuel in the tank to push thru to the fuel pump. That was with a flat out worn fuel pump. Wouldn't suck when going dry on the inlet but worked like a champ when flooded with fuel.

    YMMV!

    Jon.
     
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  8. Cat977

    Cat977 Senior Member

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    Thinking a bit on what Brock said and a bit on me, with a cavoite (I don't know much on these things). If a lift pump lives inside the injector pump assy. and its weak and the manual pump is upstream and maybe with air leaking in, it can leak air in and make things worse. Fix its packing and any other air leaks. If a small lift pump needs help park it going down hill with a full tank, and a good tank shut off valve so no worries. This should cause full flow though filter at stand still with no help.
    Best of Luck LF
     
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  9. leadfarmer

    leadfarmer Well-Known Member

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    Also the manual pump is newish. Replaced it November of 2020.
     
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  10. charles walton

    charles walton Senior Member

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    I have not talked with this fellow in about 5 years,he was in his 80's then and that was before covid. I will try to find out if he is still above ground next time I go to Ga. I moved about years ago to Tn.
     
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  11. tctractors

    tctractors Senior Member

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    By the sound of things you have a failed injector capsule, to test this point start the engine up and run it at low idle and undo each injector fuel line at the pump, look for a line that blows bubbly fuel out and makes the most fuss. tctractors. p.s. to bleed the engine easy undo the injector lines up on the head and pump the hand primer with the hand throttle in the stop position.
     
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  12. leadfarmer

    leadfarmer Well-Known Member

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    So based on this test you first describe, with the machine at low idle, loosen the injector steel line one at a time on too of the injector, and look for bubbly fuel, right? And this would indicate something bad inside the injection pump?

    regarding a lift pump, I’m not seeing one on the attached parts diagram of my pump. Theres multiple shown in the parts manual and this one looks to physically match what I have the closest, based on the shape of the fuel ratio control. So is there a lift pump on this machine? Or just gravity to the IP?

    I will do that test above, and if I see air in all the lines, then I’m back to chasing and air leak leading to the punp, and it seems the hand primer would be the most likely suspect.
     

    Attached Files:

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  13. charles walton

    charles walton Senior Member

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    That is the same type IP my 13x had and it was doing the same thing you described and it ran great after I had the IP rebuilt,just saying.
     
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  14. leadfarmer

    leadfarmer Well-Known Member

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    I wonder what the cat shop charges for that? Hmmm. Should I also have injectors cleaned/tested or anything if I have the pump off?
     
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  15. sawmilleng

    sawmilleng Well-Known Member

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    No lift pump? Should be somewhere.....I dug out my service manual for a D4D (83J series)--It has a section in it for the 3304 engine and it looks like the fuel transfer pump is located in the front of the injector pump where the injector pump bolts to the engine block...and the lines to this pump are internal passages inside the injector pump itself.

    I'm thinking the same thing a you- the air is getting in somewhere upstream of the injection pump on the "suction" side of the fuel inlet to the transfer pump. Take a look at your manual pump for leaks, or. better yet, isolate the manual pump and filter, then put compressed air on it to see what happens.

    I noticed that there is a little drain valve at the top of the injector pump body--have you tried opening that when the engine is running to see what you get out of it? Foamy fuel there will suggest the lift pump is getting air mixed in the fuel. Or the lift pump is getting worn.

    A way to test the lift pump itself would be to get a small tank, bypass your filter, and put diesel directly to the injection pump with the small tank BELOW the injector . If the machine will run properly, then the fuel transfer pump is good (by proving it can suck diesel from below). The problem is then between the injection pump and the inlet side of the filter. (if you try this be sure to be squeaky clean!!!!! You don't want to get dirt into the injectors!)

    I wouldn't chase a Cat dealer yet because you don't know for SURE that the problem is inside the injector pump. The poster who said his problem went away with a pump rebuild may have had a bad fuel transfer pump inside the injection pump which got automatically rebuilt with the injection pump.... You still aren't 100% sure of where the problem is. Want to spend 2 grand on rebuilding the pump to find you still have the problem?

    Also, once you remove the injector pump, you have a new headache of re-timing the pump when you go to bolt it back up.

    YMMV--but good luck with the troubleshooting.

    Jon.
     
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  16. Nige

    Nige Senior Member

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    If you read what tct said a bit more closely.......“By the sound of things you have a failed injector capsule”.

    Note the word injector, not injection pump. Try doing the lines test first and see what results you get.
     
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  17. Nige

    Nige Senior Member

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    #26 is the injector capsule, from its shape you can see why. Referred to in the Parts Manual as a "valve".
    IIRC the engine in your 955L is a transplant of what started life as a 4B-prefix industrial engine so who knows if the Part Number of capsule actually installed is what the 955L Parts Manual says or not.

    upload_2022-8-3_12-11-29.png
     
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  18. AllDodge

    AllDodge Senior Member

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    Had Diesel Injector Service rebuild IP on my D3. There was an issue with the face on one of the capsules and they came out and changed it. Reason for bringing it up, is after removing the line, the capsule just unscrewed out of the pump. Put new one in and and fired it back up

    Your pump may do the same
     
  19. leadfarmer

    leadfarmer Well-Known Member

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    That is the valve I open all the time when I'm priming to start or re-priming after running and power drops. And yes that is where I get the foamy fuel from.

    So how hard is it to change the lift pump?

    Can I run the machine as it is for some light work loading shale in a truck for a couple hours or am I risking more damage?

    I'm picking up a hand priming pump from the cat shop at noon today. For $150 I will toss that on and rule out the $30 aftermarket one I put on in 2020.
     
  20. Nige

    Nige Senior Member

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    I'm battling to understand why instead of throwing parts at it you wouldn't first do the test of the injectors as suggested by TCT above. It would cost you nothing and might actually steer you in the right direction.
     
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