Hydraulic problems Power Trac 1850

[wdchyd]

Not sure what the model of pump it is but it looks similar to an oil-gear piston pump, old style with swash-plate over-center design (used in closed circuit hydrostat systems)

It looks like a tennant sweeper pump I worked on a few years ago, If it is then you may have had trouble with contaminates from the drive motor repair spoil your pump....it is always best when you have drive motor issues to remove and clean, lap, reseal and reassemble pumps along with new oil and filters when doing any repairs in that drive circuit

By the sounds of it the charge pump may have locked up or your rotation group/swash plates in the pump may have failed.....or the original parts that failed in the drive motor are still floating around

If I see it correctly, the front pump design you have is a variable piston pump with over-center swash plate (connected to the lever) to give you forward and backward motion for the drive motors

 

[wdchyd]

The back and forward drive is working with electrical valves. Maybe this is something wrong with?


// PowerT1850

Oooo, Sorry i missed that......having a solenoid valve changes everything...is the output of the pump going into the inlet of the solenoid valve base??...maybe the variable pump is changing it's direction thru the solenoid....if that's the case then there should be a manual override on the end of the solenoid coils......best to try those overides while the drive wheels are off the ground

 

[wdchyd]

also, another tip......to check if the solenoid coil is electrified, use the steel blade of a pocket knife (one that a magnet will stick) and touch the end of the solenoid coil to feel the magnetism when engaged, if the coil is energized your feel it

This will not show if the valve stem is stuck in the housing, but the manual overide push pin (if it has one in the center of the solenoid coil area) may clear the condition if it is stuck.........the valve stem should be spring centered when not engaged electrically

 

[PowerT1850]

Thanks for helping me! Nice PT1850 you have Ken. Hope mine will be like this someday. I have now clean the pump as JJ told and there have been a identificaton plate at the right side. But now it is gone! Hope that Terry should answer my mails, but no success. Does he have terry@power-trac.com or have I got this wrong? I also have sent to info@power-trac.com. If I donｴt know what pump there is I think it will be hard to repair. JJ No have not three pumps, it is one dualpump and one little at the right side of engine ( Think this is the steering). I will try to make my own hyd scheme by follow hoses.
What part shall I use if/when I replace motors and pump? Maybe this ??? Surplus Center - 28.3 cu in HYD WHEEL MOTOR W/5 BOLT HUB

PT1850

 

[J_J]

Your task is not going to be an easy one as like me, I have very little documentation on my machine. My PT-1445 is an early 90's machine without the Quick Attach setup, and the only large gas engine that I know of.

You need all things working to take a reference value for pressure, etc.

For instance, if the pressure from the pump is capable of 3000 psi, and the flow is passing through two 15 cu in wheel motors in series, that means that each one of the motors is developing 1500 psi, so if you are going to replace a single motor, you have to get the same cu in motor and the correct psi wheel motor.

As with with most things, you have to know how something works to fully analyze and diagnose a problem.

Based on on what you have, some of the unknown factors can be computed, such as HP to power a pump, how much torque is needed for a motor to turn a wheel.

I now know most of the details of my PT by hands on operation, and replacing parts .

Your variable displacement pump could be made by Eaton, Char-Lyn. Wheel motors by White, Sauer-Danfoss, etc.

If you use the wrong wheel motor, your torque could be cut in half.

I think I would install a tee with a 1/4 male QD in each hyd circuit so you can plug in a 3000 psi liquid filled hyd gage and analyze the results.

When things are broke, there is very little or no reference.

Here are some pics of some hyd test sets. Should cost about $30 US

The size of the pump should be matched to the wheel motors.

Have you read through some of the Power-Trac forum post. They go way back. You can search for 1850 and maybe pick up some useful data.

Don't know the reasoning, but the people at Power-Trac do not participate in the PT forums.

If you can get a hold of Terry, he will talk to you.

Sometimes you have to drag data out of the PT folks.

The engine is the most expensive item on the PT, and then the Variable Displacement pump.

 

[wdchyd]

..............................maybe the variable pump is changing it's direction thru the solenoid........

Or maybe they are using the solenoid for "High/Low" selection.... and it's still an over-center swash plate for forward/rev..??

it all depends how it's plumbed...(motors in series for high speed vs motors in parallel for low speed)...:confused3:

 

[PowerT1850]

Hi,
Looked at the solenoids. You are right! The magnetic power workes but they seems to be stuck, have removed the colils and iron unit to make them move again. It is the solenoids that switch forwar/rev. If this dosn´t help I will lift the lid under the "speed control arm" and have a look!

PowerT1850

 

[SpringHollow]

My PTO solenoid valve has stuck several times. I was told that it was not repairable but I tore it apart each time, freed it up and reinstalled it. They were expensive so it made sense to try. Each time, they lasted for about 2 years before needing to be cleaned again. I think the main problem with mine is that 9 months can go by without using the main PTO and so the valve does not get cycled.

PTO Solenoid Repair

Ken

 

[wdchyd]

PowerT,

if the valve spool is stuck, then it's either contaminates in the oil or a burr that develops from the "Slam/Slam" when shifting....

The spools can be cleaned and checked for no hang-ups........the spool should not bind and should self-center with the internal springs

Worse case senario, those valves are easy to find replacements but SpringHollow has it right......clean it

Did you see the manual override on the ends (they may be rusted tight), that's the quickest way to free it without removing the valve

I would proceed with caution if you decide to take the cover/arm off that pump, If needed the best would be to remove the whole pump if you are going on a fishing expedition on it

 

[PowerT1850]

I have removed the pump. It was just the manual overrides that was stuck on solenoids, the electrical function is ok. I really need to know the brand of this pump ( Se picture ). Is it a good idea to have a look myself inside this or let a profesionall gay handle it?.