337 Losing Power (Tried everything) need new thoughts

[petersonnate]

I have Bobcat excavator 337 with a 4 cylinder Kubota Diesel. The problem has been going on for a year or more when it slowly started loosing power. Here are the items I've completed. 1) Put on a new cam run lift pump mounted to engine 2) Added an electric lift pump in place of the primer ball (pull through pump so I can leave it off if I want) just to see if the cam itself was worn out operating the cam lift pump (process of elimination). 3) Took injection pump off, with all injectors, had them rebuilt. 4) Installed new rings (over 400psi in all cylinders now +/- 20psi) 5) At this point brought is the the Bobcat dealer who said "you need a new pump". OK….$5600 later I get it back. Still looses power. 6) YES…..replaced all the filters Took it back to the dealer who ran every hydraulic test on it that they could, took the pump back apart again, (found a faulty pump controller), put it all back together and they (and I am too) are confident the pump side of the system is right. So right now this is how it acts. I can start it up and runs great. I have about 4 to 8 minutes of full power at which time it starts to bog down, slowly at first, then the engine starts a light knock (more like a tap…growing to a knock), if I stop digging/driving the RPM immediately goes right back up. Then if I touch one of the hydraulics is pulls back down just as fast. (in this state if I were to push the drive levers full forward it would kill the engine in about 2 ft of travel). I can limp around at this state (very very slow crawl, basically the engine cannot take any torque). The machine does have a temp gage which does show movement but not hot, the oil pressure alarm is not functional, and when its running I can grab the hydraulic return line before it goes into the hydraulic radiator with my bare hand so it is not that hot. I took the thermostat out the other day (just in case it was stuck shut…no difference). At this point I'm thinking it might be overheating (It would not surprise me if the gage is not functioning) but the radiator does not overflow when running (YES..its full), or maybe the oil pump is out (but if it was I think I would have had something real bad happen a long time ago)…… These are my current guesses…but I've been guessing for close to a year and $8000!!.... I'm hoping someone has a few thoughts that I might be overlooking. HELP PLEASE!!

 

[Tazza]

The biggest problem is you can't confirm if its the engine or a hydraulic component loading the engine down.....
You have good compression, good injectors and fuel pressure. There really isn't anything else.... If the valve clearance was out you wouldn't get the compression, but still wouldn't hurt to check it. If it got hot, you'd know, the head would have cracked.
If it was an oil pressure issue, i can't see it changine the power, it would have simply stopped working after a year i'd assume it would have locked up or rattle all the time badly.
The only thing i could think to check it would be if someone could dyno the engine, but this will cost even more. Thats assumeing you can find someone to even do it.
Does the engine smoke when it loads down?

 

[petersonnate]

The biggest problem is you can't confirm if its the engine or a hydraulic component loading the engine down.....
You have good compression, good injectors and fuel pressure. There really isn't anything else.... If the valve clearance was out you wouldn't get the compression, but still wouldn't hurt to check it. If it got hot, you'd know, the head would have cracked.
If it was an oil pressure issue, i can't see it changine the power, it would have simply stopped working after a year i'd assume it would have locked up or rattle all the time badly.
The only thing i could think to check it would be if someone could dyno the engine, but this will cost even more. Thats assumeing you can find someone to even do it.
Does the engine smoke when it loads down?

"The biggest problem is you can't confirm if its the engine or a hydraulic component loading the engine down....." Absolutely....that is the problem. Yes....engine smokes when it loads down. Forgot to mention that I have played with the fuel adjustment on the side of the injection pump, didn't really do that much (blow white or black smoke depending on the way you go), no real preformace change. Smoke is much more pronounced when engine is loading down.

 

[Tazza]

"The biggest problem is you can't confirm if its the engine or a hydraulic component loading the engine down....." Absolutely....that is the problem. Yes....engine smokes when it loads down. Forgot to mention that I have played with the fuel adjustment on the side of the injection pump, didn't really do that much (blow white or black smoke depending on the way you go), no real preformace change. Smoke is much more pronounced when engine is loading down.

I;d assume that when the engine is loading down its not a fuel supply issue as you are getting smoke. Smoke = fuel, excessive smoke is when there is too much fuel or its not being burnt fully.
I really have no idea where you can go from here, its as if there is a component causing high resistance, but to cause enough to bog the engine down it would have to be creating heat, and lots of it.
Does it have some sort of aux hydraulic connections? i wonder if its coming on some how loading the system down.
The only thing i can think to test it with is an IR thermometer. Check around the pump to see if there is a section getting hot quickly. Does it have the issue when you leave it run and not moving around?
Sorry, just throwing some ideas out there.

 

[Fishfiles]

I;d assume that when the engine is loading down its not a fuel supply issue as you are getting smoke. Smoke = fuel, excessive smoke is when there is too much fuel or its not being burnt fully.
I really have no idea where you can go from here, its as if there is a component causing high resistance, but to cause enough to bog the engine down it would have to be creating heat, and lots of it.
Does it have some sort of aux hydraulic connections? i wonder if its coming on some how loading the system down.
The only thing i can think to test it with is an IR thermometer. Check around the pump to see if there is a section getting hot quickly. Does it have the issue when you leave it run and not moving around?
Sorry, just throwing some ideas out there.

run it on a external fuel tank to eliminate things like tank vaccum ,cracked fuel lines sucking air , restriction in a fuel hose , fuel filter / head suction leak , had a Daewoo 70 did the same thing recently and it was a steel washer with the rubber insert on a banjo fitting in the fuel system that was sucking air , found it after running it with a fuel tank and all was good , intalled a clear piece of tubing into the fuel system right before the injector pump and could see the bubbles

 

[petersonnate]

I;d assume that when the engine is loading down its not a fuel supply issue as you are getting smoke. Smoke = fuel, excessive smoke is when there is too much fuel or its not being burnt fully.
I really have no idea where you can go from here, its as if there is a component causing high resistance, but to cause enough to bog the engine down it would have to be creating heat, and lots of it.
Does it have some sort of aux hydraulic connections? i wonder if its coming on some how loading the system down.
The only thing i can think to test it with is an IR thermometer. Check around the pump to see if there is a section getting hot quickly. Does it have the issue when you leave it run and not moving around?
Sorry, just throwing some ideas out there.

I was thinking that I would hook up a pressure gage back by the big hydrolic filter (take out the sensor that is not working and hook up a manual gage) to see what the pressure is beforer it goes through the cooler to the tank. I assume it should be real low at that point and if its "backing up" because it can't return the fluid to the tank I'll get some high readings. Then I would know that its between the gage and the tank at least. The reason why I think it is "heat" driven versues "back up" pressure driven is that once it starts to act up I can't shut it down for 5 minutes (ample time to blead off any pressure build up I would think) and start it up and have full power again. It takes sutting it down for an hour plus before I can start the process out again with any measurable power.

 

[Fishfiles]

I was thinking that I would hook up a pressure gage back by the big hydrolic filter (take out the sensor that is not working and hook up a manual gage) to see what the pressure is beforer it goes through the cooler to the tank. I assume it should be real low at that point and if its "backing up" because it can't return the fluid to the tank I'll get some high readings. Then I would know that its between the gage and the tank at least. The reason why I think it is "heat" driven versues "back up" pressure driven is that once it starts to act up I can't shut it down for 5 minutes (ample time to blead off any pressure build up I would think) and start it up and have full power again. It takes sutting it down for an hour plus before I can start the process out again with any measurable power.

the filter would by pass if plugged up ---I'd still look to fuel delivery ---what weight of oil you running in it -----down time , wasted money and frustrations ------$8,000 wasted so far from your story I would not trust any repairs the dealer did so far as being right and would consider myself at square one , we had two of the 337's in our rental / with operator fleet when they first came out , they didn't hold up and was traded off --------- where is your cut off point -- it's is probally not worth what you have into it at this point , so why keep piling it on ---trade it in -- Popeye said it best " Dats all I can stands and I can't stands no more " ---Grandma you say " it's hard making chicken salad when all you got is chicken $hit"

 

[xcmark]

the filter would by pass if plugged up ---I'd still look to fuel delivery ---what weight of oil you running in it -----down time , wasted money and frustrations ------$8,000 wasted so far from your story I would not trust any repairs the dealer did so far as being right and would consider myself at square one , we had two of the 337's in our rental / with operator fleet when they first came out , they didn't hold up and was traded off --------- where is your cut off point -- it's is probally not worth what you have into it at this point , so why keep piling it on ---trade it in -- Popeye said it best " Dats all I can stands and I can't stands no more " ---Grandma you say " it's hard making chicken salad when all you got is chicken $hit"

does it have a return line back to the tank for fuel ? if it does pull it off with it running to see how much fuel is returning. could be a screen in a fitting on the inlet side of the fuel system getting loaded with crap ? Have you blown air back threw the fuel pick up lines back to the tank ? could be it has a pick up sock in the tank thats is clogged? any water in the fuel filter or orange rusty crap in the filter?

 

[TrevorPilgreen]

does it have a return line back to the tank for fuel ? if it does pull it off with it running to see how much fuel is returning. could be a screen in a fitting on the inlet side of the fuel system getting loaded with crap ? Have you blown air back threw the fuel pick up lines back to the tank ? could be it has a pick up sock in the tank thats is clogged? any water in the fuel filter or orange rusty crap in the filter?

i know this is an old post but I'm having the exact problem out of my kubtoa excavator any idea if this guy fixed his?

 

[teck6]

i know this is an old post but I'm having the exact problem out of my kubtoa excavator any idea if this guy fixed his?

Check with your dealer ,at one time there was a new torque limiter from Rexroth.. Check bobcat service letter # 5217... This may be an issue depending on ser# of your unit.

 

[teck6]

Check with your dealer ,at one time there was a new torque limiter from Rexroth.. Check bobcat service letter # 5217... This may be an issue depending on ser# of your unit.

(337/341 Torque Limiter Adjustment Rexroth has designed a new torque limiter that will be a drop in replacement of the current torque limiter. It addresses customer complaint of engine bogging and erratic pump operation. See SL#5217 (EXR99) for affected range and instructions. Updated margin adjustment procedure will need to be followed if there is a need to check the setting. ) This is some info from Bobcat , hope this helps.....

 

[7LBSSMALLIE]

(337/341 Torque Limiter Adjustment Rexroth has designed a new torque limiter that will be a drop in replacement of the current torque limiter. It addresses customer complaint of engine bogging and erratic pump operation. See SL#5217 (EXR99) for affected range and instructions. Updated margin adjustment procedure will need to be followed if there is a need to check the setting. ) This is some info from Bobcat , hope this helps.....

i am in sgreement with it not being the eng but the torque limiter. is dealerr shit hot or mom and pop. the 337 as well as the 442 can be tricky to set. the service man proucd. are guidelines not gospel. you can never forget that it is perciption that rules. if the operator is happpy every one is we all know that you can as a compent operator(make no mistake im a tech not an operator) get stacking preesures at the sticks. more breakout by feathering one and strokin the other. these are things that are not published but every operator gets a feel for i have found from peronsal experiance that the best way to set some of these (finnicky units) get the operator to show what its doing.. set to factory spec , and then dial in. me i would flow check pump check main reliefs set tourque limiter. or as the s)m states (thats my start point) than i hate to say it but than i would go to digggin area and dial in on the downlow ive heard these same words from factory rep

 

[diyman]

i am in sgreement with it not being the eng but the torque limiter. is dealerr shit hot or mom and pop. the 337 as well as the 442 can be tricky to set. the service man proucd. are guidelines not gospel. you can never forget that it is perciption that rules. if the operator is happpy every one is we all know that you can as a compent operator(make no mistake im a tech not an operator) get stacking preesures at the sticks. more breakout by feathering one and strokin the other. these are things that are not published but every operator gets a feel for i have found from peronsal experiance that the best way to set some of these (finnicky units) get the operator to show what its doing.. set to factory spec , and then dial in. me i would flow check pump check main reliefs set tourque limiter. or as the s)m states (thats my start point) than i hate to say it but than i would go to digggin area and dial in on the downlow ive heard these same words from factory rep

bringing the back out, our excavator is doing a similar thing, however its a 231 excavtor. ours will bog down and have an erratic idle. we were digging a 400ft trench to lay tile and it dug fine but if we tried to move it it would bog down alot. whenever we put it on the trailer it will die unless you creep very slowly onto it. it started when my father put some bad fuel in it with some contaminents and were going to pull the fuel tank off and flush it and eplace fuel lines. im concerned he wiped out the injection pump and possibly injectors plugged up. i was told to look at the lift pump first so i will check that out

 

[Tazza]

bringing the back out, our excavator is doing a similar thing, however its a 231 excavtor. ours will bog down and have an erratic idle. we were digging a 400ft trench to lay tile and it dug fine but if we tried to move it it would bog down alot. whenever we put it on the trailer it will die unless you creep very slowly onto it. it started when my father put some bad fuel in it with some contaminents and were going to pull the fuel tank off and flush it and eplace fuel lines. im concerned he wiped out the injection pump and possibly injectors plugged up. i was told to look at the lift pump first so i will check that out

I'd hope the filter got any water/muck before it got the the pump. I'd check the pickup screen was clear of junk though. If it is clogged up, it will cause issues. You can always try by-passing the fuel tank with a jug of fuel, see if it bogs on a fresh fuel supply. Remember to change the filter before you do this, then you know it's spotless.

 

[diyman]

I'd hope the filter got any water/muck before it got the the pump. I'd check the pickup screen was clear of junk though. If it is clogged up, it will cause issues. You can always try by-passing the fuel tank with a jug of fuel, see if it bogs on a fresh fuel supply. Remember to change the filter before you do this, then you know it's spotless.

ill have to try that with a good tank of fuel. .does anyone know the exact locations of some of the fuel screens?

 

[Tazza]

ill have to try that with a good tank of fuel. .does anyone know the exact locations of some of the fuel screens?

I would have suspected just one in the tank. That gets the bulk of it, the smaller bits are caught by the fuel filter.

 

[7LBSSMALLIE]

I would have suspected just one in the tank. That gets the bulk of it, the smaller bits are caught by the fuel filter.

guts its the torque limit , unfourntaly setting to spec wont help you here its a balance thing,(eng wear hyd wear ,)needs to be dialed in, this is one of those cases that going buy the book is no help . takes a been there done it approach, facts ..a compresion good.b filters changed on hyd sys including case drain? pumps have been flow checked? (working at 80% or better) tazz we have talked for quit some time now i no you got game,, toss the book and run on instincit, the setting of tourqe is a two step procecces., im at the house not the shop so no access to man but you been in it so you know, man states a starting point(its listed as fact but this is not the case its a starting point) trust youre instincts , screw with the screws till it gets happy,(a proper balance between hyds and eng lug) is what youre looking for. results = success,

 

[7LBSSMALLIE]

guts its the torque limit , unfourntaly setting to spec wont help you here its a balance thing,(eng wear hyd wear ,)needs to be dialed in, this is one of those cases that going buy the book is no help . takes a been there done it approach, facts ..a compresion good.b filters changed on hyd sys including case drain? pumps have been flow checked? (working at 80% or better) tazz we have talked for quit some time now i no you got game,, toss the book and run on instincit, the setting of tourqe is a two step procecces., im at the house not the shop so no access to man but you been in it so you know, man states a starting point(its listed as fact but this is not the case its a starting point) trust youre instincts , screw with the screws till it gets happy,(a proper balance between hyds and eng lug) is what youre looking for. results = success,

meant to bring book home forgot, got handwritten notes in but any way,i neglected to mention pump margin spool limit and margin work hand in hand,

 

[7LBSSMALLIE]

guts its the torque limit , unfourntaly setting to spec wont help you here its a balance thing,(eng wear hyd wear ,)needs to be dialed in, this is one of those cases that going buy the book is no help . takes a been there done it approach, facts ..a compresion good.b filters changed on hyd sys including case drain? pumps have been flow checked? (working at 80% or better) tazz we have talked for quit some time now i no you got game,, toss the book and run on instincit, the setting of tourqe is a two step procecces., im at the house not the shop so no access to man but you been in it so you know, man states a starting point(its listed as fact but this is not the case its a starting point) trust youre instincts , screw with the screws till it gets happy,(a proper balance between hyds and eng lug) is what youre looking for. results = success,

question could this be more of a black stacking rather than a power issue? as in hyd are demandining more than eng can deliver, therby bogging eng down and throwing smoke? or is it the other way as in eng cant deliver . but you ran comp check on eng,(right) did all the fuel and air things? confirmed no parristic load as in alt or wp..