JD 755 losing power under load/ HELP

[rkelly12]

I have a JD 755 hydro. It is losing most of it's power, almost to a stop, when going up slight inclines or if I press the forward pedal to quickly. Under this circimstance, it also produces a lot of black smoke. It seems to worsten if I am turning the power steering (using hyrdaulics) during the climb. Under load, it seems to lose significant power when using a mower. Without moving, hydraulics work fast and fine, no smoke, etc. Moving on flats it mostly ok unless I try to go to fast, then it loses.

I changed fuel filter, oil, oil filter. Trans fluids are at a good level and looks clean. Front axle fluid is ok. Put in new diesel gas yesterday with cleaner stuff in it. Seems like less black smoke, but still lose of power. Under a fast idle I loosened each of the injector bolts a bit and it quickly made a difference on all three cylinders so it seems like they are working. This does not burn any oil so I'm hoping compression is ok.

Can anybody help with what the problem may be?
Thanks much.

 

[Hambone]

How many hours?

 

[jd110]

You didn't mention the air filter. Is it clean? You might have a primary and secondary air filter. Check them both. Also check for any obstruction in the fuel line. Another thing you might want to check is the brakes. If they are dragging, it will drain your power. Put your high and low range lever in neutral while on a level surface. The tractor should roll easily when pushed by hand. One last thing to check is the hydraulics. Make sure the rockshaft is not in relief or the scv lever is not sticking on.

 

[rkelly12]

Steve - I'm not sure how many hours are on this machine. I purchased it used about 4 years ago and supposedly it came from a college in the midwest. I think the hour meter says 2600+. I don't know if this is accurate and I don't know what the service history is like.

Any ideas?
Thanks.

 

[rkelly12]

With the machine in neutral it rolls easily and it seems like the brakes are not dragging. Air filter is about 6 months old and seems to be fairly clean. I'm not sure if there is supposed to be a primary and secondary - it only has what looks like the secondary air filter on it. The larger diameter air filter with the "ribs" on it. The smaller (primary?) filter was not on this machine when I purchased it so I've only replaced the outer, larger filter. Stupid question - what/where is the rock shaft and the scv lever? Any help is appreciated. Hydraulics seem like they are are working correctly.

 

[rkelly12]

In neutral it rolls easily and it seems like the brakes are not dragging. Air filter is about 6 months old and seems to be fairly clean. I'm not sure if there is supposed to be a primary and secondary - it only has what looks like the secondary air filter on it. The larger diameter air filter with the "ribs" on it. The smaller (primary?) filter was not on this machine when I purchased it so I've only replaced the outer, larger filter. Stupid question - what/where is the rock shaft and the scv lever? Any help is appreciated. Hydraulics seem like they are are working correctly.

 

[rkelly12]

- JD110 -
Your Awesome!! My aircleaner is clean but I took your advice and checked out the gas tank and screen inside the tank. I removed the tank and poured its contents through a screen out came a spring, some leaves, muck, a screen not attached to the suction tube, a piece of rubber and a lot of mucky junk. Must have had a college kid using it at the college it came from. Cleaned it all out, reattached the screen and it ran a lot better, but still lost some power on uphills. Then I checked the brakes like you said and low and behold, I could not move the machine when it was in neutral. I removed the brake linkages to fully release the brakes and I could push the machine. My first ride says that it is much much better now. Less smoke too. Anything else I should check? Do I ever have to do anything to the injectors?
Thanks Alot!!
Rob Kelly

 

[jd110]

One other thing occurred to me after i posted the first time. Be sure the exhaust is not restricted. A bent or kinked exhaust pipe can really hurt power and cause exceesive smoke. On 850's and 950's I have seen the mufflers clog internally with soot. Never saw this happen on 755 though I suppose it is possible. As far as the injectors, they are pretty reliable but they do sometimes go bad. You said you loosened the fuel lines one at a time to check for misfire, that should prove the injectors are ok but they can get partially bad and cause loss of power and excessive smoke without causing a dead misfire. The only real way to check them is remove them from the engine and take them to your dealer or a diesel shop to have them tested.Might not be a bad idea if things don't seem 100% after you eliminate everything else.

 

[BigEddy]

Make sure you install the secondary filter as well. That's critical to protecting your engine. The secondary is there to ensure that the finer dirt that makes its way through the primary does not end up in your engine. Cheap insurance.

Big Eddy