Deere 710c backhoe hard start issue.

[tazz001]

90 Deere 710c has had start issue.

Has new batteries, cabling in good shape, new starter. extra ground cables put on. and still starts hard. It starts like the batteries are weak (yes new batteries have been tested).

It will crank better with the farm fix of wiggle the steering wheel so its seems like it's hydraulic related. It seems like the unloader solenoid is working (its on the main pump).

What has us really scratching our heads is there is a power steering pump that is belt driven??

Why would steering wheel jiggle work for starting issue?? I'm confuzzeld or are we overlooking something in the hydraulic system..

Can anyone please explain?? throw me some ideas

 

[texasranger556]

Based on what you've described I would take the belt off the ps pump and see if the starting behavior improves. It could be something in the pump or valve restricting flow and causing it to run over relief all the time.

 

[tazz001]

That is not happening. The main hydraulic pump will have to come off to remove the belts.. Which means removal of all the front end weights.. Possibly radiator..
Further research.. The parts manual calls the PS pump a steering charge pump..

 

[texasranger556]

Looking through the parts diagrams it's more complicated than I was thinking. The belt drive pump must charge the main pump as well as the steering valve. There's a priority valve involved too and I haven't dealt with those before to try helping without a schematic. I'm sure there are others that will chime in though!

 

[tazz001]

Complicated is putting it midly.. Public forum would frown on way I am thinking. 450b dozer needed new crank driven pump last summer.. That was bad enough..
Chased pressure line and it appears to go to steering..

 

[Tx Jim]

My knowledge of JD ind tractors is very limited but I do understand closed center hyd's. I don't understand the need for a steering charge pump on closed center hyd system. Turning steering wheel back & forth during starting process relieves pressure buildup and to my knowledge was originated by a JD representative not a farmer. What indicates destroker valve is operating correctly? Have you checked voltage to it? How did you check it's operation? It sounds to me that the de-stroking valve is inoperable.

 

[texasranger556]

My guess is the belt drive pump through the priority valve charges the main pump but also supplies the steering valve which is probably an open center valve. Hence the name. Just a guess though.

 

[Zebrafive]

My knowledge of JD ind tractors is very limited but I do understand closed center hyd's. I don't understand the need for a steering charge pump on closed center hyd system. Turning steering wheel back & forth during starting process relieves pressure buildup and to my knowledge was originated by a JD representative not a farmer. What indicates destroker valve is operating correctly? Have you checked voltage to it? How did you check it's operation? It sounds to me that the de-stroking valve is inoperable.

Not up on industrial either! So just a GUESS; "steering charge pump" pump may not be a steering charge pump, but a charge pump for the main pump, instead of an internal transmission pump that older JD AG tractors have. Since this is designed to sit in one place and dig for long periods of time.

 

[Tx Jim]

Zebrafive
Below is parts schematic of for 710C trans pump

 

[Zebrafive]

Zebrafive
Below is parts schematic of for 710C trans pump

Thanks, TxJim, as I said, I am not up on the Industrials, especially the one that did not "morph" from AG tractors.