Case 75xt won't run at low RPM

[lewispmills]

My Case 75xt will start up but revs when started whether you are giving it fuel or not but immediately dies. If you give it about half throttle it will run but not well. It will operate this way but is low on power. I have changed the lift pump and filters including the air filter, nothing helps. I have "cracked" the high pressure lines and all seem to squirt equally and seem to affect the engine roughness the same. I had a diesel mechanic look at it and he has never seen this before but recommended removing the injector pump and having it rebuilt. I'm ok with that but thought I might see if you guys have any other suggestions before I go to that expense? Any help would be appreciated!
Lou

 

[foton]

My Case 75xt will start up but revs when started whether you are giving it fuel or not but immediately dies. If you give it about half throttle it will run but not well. It will operate this way but is low on power. I have changed the lift pump and filters including the air filter, nothing helps. I have "cracked" the high pressure lines and all seem to squirt equally and seem to affect the engine roughness the same. I had a diesel mechanic look at it and he has never seen this before but recommended removing the injector pump and having it rebuilt. I'm ok with that but thought I might see if you guys have any other suggestions before I go to that expense? Any help would be appreciated!
Lou

I would think you might have a problem before the lift pump,like a restricted fuel pick up in tank maybe? cause your description to me sounds like it is running lean. can you plumb in a pressure gauge between the lift pump and the injector pump to see if the pressure there jives with the factory pressure specifications.

 

[lewispmills]

I would think you might have a problem before the lift pump,like a restricted fuel pick up in tank maybe? cause your description to me sounds like it is running lean. can you plumb in a pressure gauge between the lift pump and the injector pump to see if the pressure there jives with the factory pressure specifications.

Thanks for your response, I don't have the fixtures to do that but could get them.
When it is running at high RPMs, you can loosen the feed bleed screw and it will squirt fuel so I think it's getting fuel from the lift pump. If it wasn't it should run out of fuel at high RPMs but it doesn't. It only occurs at low rpms. The mystery to me is why it revs on startup even if you aren't giving it any throttle????

 

[[email protected]]

Thanks for your response, I don't have the fixtures to do that but could get them.
When it is running at high RPMs, you can loosen the feed bleed screw and it will squirt fuel so I think it's getting fuel from the lift pump. If it wasn't it should run out of fuel at high RPMs but it doesn't. It only occurs at low rpms. The mystery to me is why it revs on startup even if you aren't giving it any throttle????

Is there a governor on this machines engine? Kind of sounds like it's possible. Just a quick thought.

 

[lewispmills]

Is there a governor on this machines engine? Kind of sounds like it's possible. Just a quick thought.

I'm not sure. Just a little more history, the first time it did this was last spring it was cold and it has a button on the control beside the light switch that you can push to get more fuel for cold starts and I used it and it started but wouldn't run right so I didn't use it. When it warmed up it started and ran fine for a couple months. Now it is pretty much unusable. It will run at half throttle but doesn't have much power and will constantly die and you have to restart. ????? It's certainly not good on the engine the way it revs when you start it cold.

 

[foton]

I'm not sure. Just a little more history, the first time it did this was last spring it was cold and it has a button on the control beside the light switch that you can push to get more fuel for cold starts and I used it and it started but wouldn't run right so I didn't use it. When it warmed up it started and ran fine for a couple months. Now it is pretty much unusable. It will run at half throttle but doesn't have much power and will constantly die and you have to restart. ????? It's certainly not good on the engine the way it revs when you start it cold.

with that extra info. then I would say the mech. might be on the right track as to the injector pump as I believe that the governor is in the injector pump housing. but that would only explain the erratic throddle response unless there is further damage to the internals of the pump. If you go down the injector pump road make sure you use a good company to do the rebuild as it takes pretty expensive equipment to properly set up these pumps to get them right.

 

[lewispmills]

with that extra info. then I would say the mech. might be on the right track as to the injector pump as I believe that the governor is in the injector pump housing. but that would only explain the erratic throddle response unless there is further damage to the internals of the pump. If you go down the injector pump road make sure you use a good company to do the rebuild as it takes pretty expensive equipment to properly set up these pumps to get them right.

Thanks for the input, I was pretty certain that was the answer but I sure wish it was something less expensive.

 

[foton]

Thanks for the input, I was pretty certain that was the answer but I sure wish it was something less expensive.

while you are at it if you are gonna have the pump rebuilt you might as well take the injectors down there to get them checked out also.

 

[lewispmills]

while you are at it if you are gonna have the pump rebuilt you might as well take the injectors down there to get them checked out also.

I never thought about that, good suggestion.

 

[lewispmills]

OK guys, I need help! This is an update on a 3 month post so don't know if I'll get a response or not, but worth a try:
I replaced the fuel lines and lift pump again. Sent the injector pump to a reputable rebuilder and had it rebuilt also sent the injectors and had them refurbished. Didn't change anything! Sent it back and the rebuild shop checked it again and swears the pump is good. The lift pump pumps up solid and will remain that way for days. The machine starts easily and still revs even if you don't give it throttle, but dies immediately. If you give it half throttle it will remain running and you can slowly lower the rpm's and it will idle. But when you increase the RPMs and let off it will die every time. I've adjusted the idle screw and that increases the RPMs but don't keep it from dying. I bought a service manual but it doesn't have anything in it about the fuel system. Does anybody have any suggestions? I'm all out of ideas!!!!

 

[Firefighter]

OK guys, I need help! This is an update on a 3 month post so don't know if I'll get a response or not, but worth a try:
I replaced the fuel lines and lift pump again. Sent the injector pump to a reputable rebuilder and had it rebuilt also sent the injectors and had them refurbished. Didn't change anything! Sent it back and the rebuild shop checked it again and swears the pump is good. The lift pump pumps up solid and will remain that way for days. The machine starts easily and still revs even if you don't give it throttle, but dies immediately. If you give it half throttle it will remain running and you can slowly lower the rpm's and it will idle. But when you increase the RPMs and let off it will die every time. I've adjusted the idle screw and that increases the RPMs but don't keep it from dying. I bought a service manual but it doesn't have anything in it about the fuel system. Does anybody have any suggestions? I'm all out of ideas!!!!

did u get it resolved, it would sound like the rail/rack that controls the fuel volume is stuck or sticking, if not that it could be governor flyweights or springs or internal linkages badly worn, the issue with lower power or stalling normally comes from a really sluggish or stuck rail

 

[06Ram3500]

Sounds like you're sucking air between the tank and lift pump. Take a 5 gal. Bucket with fuel, A hose long enough to reach the lift pump and try that. Also check the original fuel lines for rust and deteriorated rubber hoses.

 

[lewispmills]

did u get it resolved, it would sound like the rail/rack that controls the fuel volume is stuck or sticking, if not that it could be governor flyweights or springs or internal linkages badly worn, the issue with lower power or stalling normally comes from a really sluggish or stuck rail

I had the pump rebuilt ($1300) by a supposedly "reputable" shop and it didn't change anything. Sent it back to them a second time and they say nothing is wrong with it. I've done the "bucket trick" twice and didn't change a thing. I've got a tractor with the same pump and I guess I'll take the pump off it and try it before buying another pump. That's all I know to do??? This thing is about to wear me out, lots of hours and money spent.

 

[lewispmills]

Sounds like you're sucking air between the tank and lift pump. Take a 5 gal. Bucket with fuel, A hose long enough to reach the lift pump and try that. Also check the original fuel lines for rust and deteriorated rubber hoses.

I've done the "bucket trick" twice and still the same thing. I replaced the lift pump and all the lines back to the tank. Blew air back into the tank to make sure there wasn't a blockage but no change. Thanks for the suggestion.

 

[lewispmills]

Any suggestion on a reputable place to buy a refurnished pump?

 

[06Ram3500]

Did you put additives to your fuel and possibly lose the foil seal from a bottle? If not I've seen cracked pickup tubes do what your saying.

 

[Firefighter]

I've done the "bucket trick" twice and still the same thing. I replaced the lift pump and all the lines back to the tank. Blew air back into the tank to make sure there wasn't a blockage but no change. Thanks for the suggestion.

Does it have the inline piston pump or is it a rotary, they used both. if it is the inline pump u could pull the cover off the side , and check the rail to see if it moves freely, also make sure the fuel solenoid is opening the fuel completely, that can also cause running & power issues