PB drive troubleshooting

[towermonkey1]

All right fellas here is a new one - PB280d drive issues. My operators are complaining that the 280 is losing power. My ride along with them I didn't notice a loss of engine speed, or any type of lugging, but distinct loss of forward momentum, when traveling up hill.

When first staring out the machine operates just fine, but then begins to fade as the shift progresses. Also noted when coming downhill it feels like the machine is freewheeling and there is an increase in engine rpm, almost uncontrolled.

Operators say there is no hydraulic functions when this happens, ie steering, but the tiller continues to spin. I have not experienced this aspect but have noted the freewheeling sense. Got any ideas Guys?

We don't have test gauges to perform checks our selves and will have to call a local equipment service or PB service which comes from Burnsville,MN cost us about 2 Grand just to get them here. Almost prohibitive for us.

[Tom400CFI]

I'm not sure what's going on, but here is what I would do first and why;
It's possible for engine power to be the cause of the problem, but not manifest itself in lost RPM. Why? B/c the drive card will de-stroke the pumps to maintain desired RPM (as per the Throttle position sensor). I've had this happen before where the motor didn't produce any HP, but DID run the desired RPM.

Put the drive card into "Hand" mod (manual drive) and keeping in mind all safety concerns go drive the cat. "Manually" stroke the pumps using the speed pot. If the engine is the issue, it will fall on it's face. Other wise, you know you have a drive system problem. Post back the results we can go from there.

You can't get some 10,000 PSI gauges from your local auto parts store? (to test the drive system)

-Tom

[troutriver]

Here is what you need for hydraulic testing of the drive or implement hydraulics. It is a complete kit with gauges, hoses and adapter fittings for "minimess" test ports. If you have PB's, don't screw around, just get this kit from the branch in MN. The part number is 8.455.290.000 for $620. I don't think you will find a better kit for the price, I have tried. (If someone has-let me know please!!) On a side note, all this stuff can be used to test Bobcat, Volvo and other heavy equipment. Prinoth is going to the same "minimess" ports on some new cats and in future production after talking to one of their techs.

Its alot of money, but the "minimess" testing ports used on most Rexroth pumps and German valves are not something you are just going to attach a normal gauge to. I tried. You can "T" into lines with some DIN to NPT or ORBOSS fittings and convert to US hoses/fittings/guages from there, but its a pain.

Good luck

[troutriver]

Just a side note...since Bobcat, Volvo and some others use the same testing ports, perhaps you can find some hoses/gauges closer to home from a contractor or machinery dealer mechanic to use/borrow/buy?? Just a thought. I don't dare make any guesses as to the problem with no specs on your drive/charge/case pressures. The advice from Mr Tom sounds like a simple place to start.

[Jimski]

one more thing to check would be the boost pressure of the intake. I have seen cats with exact same symptoms and it turned out to be a crack in the boost pipe. I have also seen the boost hoses fail. The best way to test the boost pressure on a new generation pb200 is with a mini diag, it will read the boost pressure as you put the machine underload, but since this is not possible with PB280, visually inspect the boost hoses, and take the pipe off, plug both ends, and put it in a bucket of water to see if you get and bubbles. The only thing that stumps me would be the down hill symptoms of loosing the steering, but I could see if your boost was really low, and you drop your RPM's on a downhill pass, you may feel a loss in steering sensitivity.