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Discussion Starter · #1 ·
Hello- I'm new to the forum and am having a problem with my 80's 410 D. My son was cutting in his new driveway when it suddenly stalled. It would not even turn over, only click at the starter. I troubleshot the electrical, and couldn't find a problem. I started to suspect a hydraulic load on the front pump so I tried to start it while moving each control valve, no luck. I removed the pump coupler to isolate the engine, and it started right up. I can't rotate the pump shaft at all.

I assume something is locked up in the hydraulic system, but I'm not sure which way to go next. My hunch is to crack a high pressure line to relieve any pressure that could be against the pump, and try to rotate the pump manually. That should tell me if the pump is locked or if it's somewhere in the system. However, I'm not excited about cracking a line with unknown pressure in it. I'm not sure how to relieve possible pressure safely.

Some forums have suggested a pressure gauge check, but most of them are for a tractor that is running. Any suggestions on which way to go next?

Thank you!
 

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Don't go looking for problems that don't exist. You found your problem when you removed the pump and the engine could be started.

There is no pressure buildup in the lines other than what gravity applies to implements that have been raised above ground. The amount of pressure that would kill a 90 hp engine would, in all probability, break the pump. That is why there is a relief valve in the system. It keeps the pressure below that which will damage the pump. Relief valves are designed to fail in an open position so that there is no pressure build up to do that kind of damage. The pumped fluid all goes back to tank as the path of least resistance.

Disassemble and repair the pump. If it can't be repaired, replace it.
 

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Discussion Starter · #3 ·
Thanks for the answer. (I do feel like you slapped my hand with a ruler) but you were absolutely correct. I pulled the pump and it's seized. Thanks again.
 

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Sorry about that. It wasn't my intention. There are more than a few members with hydraulics problems that have gone looking for the complicated solution when it is actually quite simple if you have just a small amount of hydraulics knowledge.

  • Reservoir level acceptable. Check!
  • Pump is turning. Check!
  • Relief valve clean. Check!
  • Control linkages free to move, Check!
  • Spool end caps clean inside and centering springs as well as detent balls and springs clean, intact, and functional. Check!
  • Cylinders drifting down due to worn seals. Check!

In your case, it was the second item on the list. It couldn't be the first item since the engine stalled. Oh yeah, the list changes depending on what the symptoms are, but the first item is on all of the lists, and the second item is on most.

BTW, I missed answering your question on "cracking a line with unknown pressure in it. I'm not sure how to relieve possible pressure safely."

The simple answer is, move the valve control handles to all positions. This will bleed off any fluid under pressure back to the reservoir.

The slightly more complicated answer. If there are no valves that can dump fluid back to tank, such as when attempting to hook up a backhoe, wrap a rag around the wrenches on any fitting and crack the line. Hydraulic fluid is incompressible for all intents and purposes. A couple of drops of fluid released will bring the pressure down to zero if the lines are steel. If hoses are involved, it will take a few more drops since pressure will expand the hoses so they act like an accumulator. The drops often come out as a short duration spurt. For most tractor lines, the volume necessary to bleed off pressure won't fill a thimble from your mother's sewing kit. Of course, if the cylinder involved is not in a 'rest' position, enough fluid will come out to park it in a 'rest' position. For the lift arms of a FEL with the bucket raised to the max height, this could be a lot of fluid to drop it to the ground. For the FEL on my GT, that could be as much as 5/8 of a quart.

The wearing of safety glasses and gloves is recommended for bleeding pressure from lines. Even a short duration spurt of high pressure fluid can pierce bare skin.
 
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