751 hydraulics "died", light is on

[Jason9500]

Hi guys, Got a 1300 hour 751 Pug (Iknow but it was cheap and I have put 400 hours on it without a hiccup till now). Ran perfect, was just grading my driveway, parked it, then went out the next day. Starts perfect but the bottom red light stays on and no hydraulics of any kind work. Tilt, lift, drive, etc is all dead as if it were electrical and someone blew a fuse. I checked everything visually and didn't see a problem. I also replaced the pressure sensor located directly under the hydraulic filter as it seeems to be a common problem and due to its age I felt it needed it anyway but that did not work. Fluid is full. Filter has about 250 hours on it. I have not changed the drain case filters but wasn't sure if they could kill the system. I took the plastic cover off the right side of the engine (drive belt I assume) and it feels tight. I am mechanically inclined. I rebuilt by lift and tilt spools and fixed the detent float functions without a problem and those have been working good for the last 200 hours so I can work on this ok but I am not a great troubleshooter as I am still learning something new everyday about he hydraulic side. All the lights are on beside the seat when the engine is running and the seat bar is down. Am I missing something here? Is there any other sensors or something electrical that would kill the system? Could it actually be a stopped up filter with 200 hours on it? If you guys can tell me anything else to check I would greatly appreciate it. This forum is awesome for info and I have learned more on it than any other forum. Thanks in advance. Jason

 

[Bswwood]

I would of thought drive belt but you checked that. Can you see the drive belt turning the pump while engine is running? Might have a pulley issue at the pump. Does it try to drive at all?

 

[Jason9500]

I would of thought drive belt but you checked that. Can you see the drive belt turning the pump while engine is running? Might have a pulley issue at the pump. Does it try to drive at all?

I partially pulled back cover to check drive belt. It felt snug. But it was not turning while the engine was running. Yeah I tried to drive it. Everything hydraulic related was dead. Thanks Jason

 

[Tazza]

I partially pulled back cover to check drive belt. It felt snug. But it was not turning while the engine was running. Yeah I tried to drive it. Everything hydraulic related was dead. Thanks Jason

If the belt wasn't moving when the motor was running, it has to be the belt, get the cover all the way off, I know it's a pain to do, but get it off and make sure.
As it starts, the fly wheel spins, the pullet is part of the fly wheel, so for the motor to run, but belt not to move, the belt has to be the issue.

 

[Jason9500]

If the belt wasn't moving when the motor was running, it has to be the belt, get the cover all the way off, I know it's a pain to do, but get it off and make sure.
As it starts, the fly wheel spins, the pullet is part of the fly wheel, so for the motor to run, but belt not to move, the belt has to be the issue.

Thanks. I will check that. It is probably due for a new belt anyway if I have it apart. Thanks Jason

 

[Jason9500]

Thanks. I will check that. It is probably due for a new belt anyway if I have it apart. Thanks Jason

To those that responded thank you. It was the drive belt tensioner pulley. Not sure why is suddenly quit working. It is the spring tensioner type. Didn't take a lot of adjustment and it seems to run great now. My guess is the the spring inside maybe slipped or is getting ready to go bad. Thanks again Jason

 

[Tazza]

To those that responded thank you. It was the drive belt tensioner pulley. Not sure why is suddenly quit working. It is the spring tensioner type. Didn't take a lot of adjustment and it seems to run great now. My guess is the the spring inside maybe slipped or is getting ready to go bad. Thanks again Jason

Gad you got it running again and that it was simple. The belt needs to be quite tight to run right.
Hopefully it was just stuck and it has settled into place now and that the spring is not on the way out, tensioners are more expensive than they should be.