Help! JD 770 Dead!

[irwin]

I sold my 770, and all my manuals went with it. So I can't do reasearch for you, just basic inspections..

First DISCONNECT THE BATTERY, then see if you can manually turn the engine over fairly easily. If yes check the starter, and all related electrical wires , components etc., If not....perhaps/maybe something was damaged with the hydro pump -let us know what you find.

Here's a link to Deere parts look up ( hydraulic pump) John Deere - Parts Catalog

 

[AKfish]

I had a battery blow up by over loading it and it made a loud pop...

Yup.. that's why I asked if his battery was still in ONE piece! You can still get some output from a blown battery - certainly not enough to crank the engine over!

I don't seriously believe he either "burned" or broke the drive shaft on the hydraulic pump(s), either. It takes some time to do that... a few seconds generally won't lock everything up that tight!

He's got something "toasted" with his electrical system and the front panel/fuse box area is a good place to be looking - IMO.

But turning the engine over by hand is a good way to eliminate a broken pump shaft from the list of problems. It's a PITA to get a wrench (big) on the front of the crankshaft to get it done, though.

AKfish

 

[kennyd]

My guess is you have blown up your hydraulic pump and it has now locked up the engine. This is a very common mistake many make when not familiar with hydraulic systems. When you disconnected your hoses it left no where for the fluid to go because its a open center system. (A open center system constantly has fluid circulating and when a action is called for like to lift the FEL it diverts the fluid to that component while normally if nothing is being used the pump is simply circulating the fluid through the system and back to the reservoir tank.) In a split second you fried the pump. This is going to be expensive. Probably a new pump and replace the fried electrical components. The last pump I replace for a friend just due to age was nearly $800. The pop you heard was a electrical component blowing when you tried to start a stuck engine. The engine is stuck due to the locked up pump.

Chris

That scenario is unlikely on his John Deere tractor, there is a main system pressure relief valve. I have heard of this happening on Chinese tractors though.

 

[Whitey]

OK.......did I tell you that the tractor is at the other end of my property in an old building.......no lights.....leaky roof.....scheduled to be torn down this year! I took a ratchet and turned the engine one full revolution with ease.....I guess dissconnecting the battery would have been smart.....but I am not smart. This tractor is a gear drive so it does not have a hydro pump. I do not know how to check the starter.....but I am willing to learn. I still do not understand why I had lights for a while when I jumped the starter and now nothing

Just for the record.......I rechecked the key switch and have voltage as my son turns the key. All fuses are good......funny thing now I cannot jump the starter anymore.......and when I put the negative side of the tester on the selenoid and the positive at the lead......shows voltage which means something is closed? if it were open it would not register voltage.

 

[kennyd]

He's got something "toasted" with his electrical system and the front panel/fuse box area is a good place to be looking - IMO.

AKfish

I agree, there is a electrical problem somewhere...

 

[Diamondpilot]

OK.......did I tell you that the tractor is at the other end of my property in an old building.......no lights.....leaky roof.....scheduled to be torn down this year! I took a ratchet and turned the engine one full revolution with ease.....I guess dissconnecting the battery would have been smart.....but I am not smart. This tractor is a gear drive so it does not have a hydro pump. I do not know how to check the starter.....but I am willing to learn. I still do not understand why I had lights for a while when I jumped the starter and now nothing

Just for the record.......I rechecked the key switch and have voltage as my son turns the key. All fuses are good......funny thing now I cannot jump the starter anymore.......and when I put the negative side of the tester on the selenoid and the positive at the lead......shows voltage which means something is closed? if it were open it would not register voltage.

When we are talking Hydro Pump we are not talking about a hydrostatic drive pump, we are talking the pump to make things like the 3 point, FEL, and rear remotes work.

Chris

 

[AKfish]

I took a ratchet and turned the engine one full revolution with ease.....I guess dissconnecting the battery would have been smart.....but I am not smart. I still do not understand why I had lights for a while when I jumped the starter and now nothing
funny thing now I cannot jump the starter anymore.......and when I put the negative side of the tester on the selenoid and the positive at the lead......shows voltage which means something is closed? if it were open it would not register voltage.

If your battery was low to begin with; your lights could be dim enough that you'd really have to look hard to really know if they were on or not. Especially during the day.

It's possible that your starter is now stuck (engaged) onto the flywheel. That could be the reason you can't jump it and it shows voltage but no cranking.

Sometimes you can disengage a stuck starter by jumping the selenoid terminals - "quickly"! And only momentarily. The idea is to get the starter motor to "jump" or quickly engage and disengage. To jump the selenoid - I've always used a long screwdriver and crossed the large cable (battery) terminal with the small terminal. You'll get some sparks and the starter should jump.

AKfish

 

[irwin]

OK.......did I tell you that the tractor is at the other end of my property in an old building.......no lights.....leaky roof.....scheduled to be torn down this year! I took a ratchet and turned the engine one full revolution with ease.....I guess dissconnecting the battery would have been smart.....but I am not smart. This tractor is a gear drive so it does not have a hydro pump. I do not know how to check the starter.....but I am willing to learn. I still do not understand why I had lights for a while when I jumped the starter and now nothing

Just for the record.......I rechecked the key switch and have voltage as my son turns the key. All fuses are good......funny thing now I cannot jump the starter anymore.......and when I put the negative side of the tester on the selenoid and the positive at the lead......shows voltage which means something is closed? if it were open it would not register voltage.

Yes it does have a hydro pump, it runs the loader and the power steering, and the 3pt hitch ..but not *important if it turns over easily (*I hope)
It's sounding more like a electrical issue..the starter should be tested off the engine, AFTER you make sure your battery and connections are good. This means either putting a different known good battery in there, or testing the battery with a load tester that reads amps. Here's hoping for something simple and not a hard to isolate poor connection .. the pow noise is a clue here..if you can find it....Starter problem? battery problem? ignition switch problem? something else?

The starter and the battery are good places to start if the ignition switch is giving 12 volts to the trigger post on the solenoid. The battery because 12 volts does not mean it has enough amps.

 

[Diamondpilot]

I think the clue here is he unhooked the hydro lines off the remotes and the ENGINE labored. He then shut if off and when he tried to restart he heard the pop!

This sequence makes me thing the pump is or was stuck. Seems not to be now since he can turn it by hand with a wrench. Sometimes when a pump goes it will contaminate the engine with hydro oil. This can lock an engine also like when water gets in there. Check your engine oil level, if its high you have your answer. Your hydro oil will be low and its time for a pump.

My feeling is when the engine was stuck something electrical got fried. Now what that is is a mystery? Like others said start with the battery, then the starter, and on down the line.

Chris

 

[Diamondpilot]

That scenario is unlikely on his John Deere tractor, there is a main system pressure relief valve. I have heard of this happening on Chinese tractors though.

I agree a pressure relief should have caught it if equipped but isn't a 770 a re badged Yanmar? I am familiar with a 790 but not the 770 so much.

The problem with a Chinese tractor is not having a PR valve but where it is. On my Jinma it is after a QC where the remotes is tapped off of. It really needs to be the first thing in line with the pump. I have re-plumbed mine to prevent Dead Heading.

Chris