pt-425 will not move forward or reverse

[ca956]

hi fellows,
I just received my new pt-425 on July 2.
I have used it to mow my lawn once, it only has 5 hrs on it.
The machine works great except when you first start it up, it will not move forward or backward. The steering, pto and all hydraulics seem to work fine. But if I push the pedal forward or reverse it will not move. After a few minutes it will start to move very slow and it will eventually move full speed.
But when you approach a hill it slows back down and jerks it's way to the top.
After it warms up completely, it seems to be fine.
I check the hydraulic fluid level and it's full.
I received no owners manual or parts manual and Power-Trac
is closed this week.
Any help would be greatly appreciated.
thank you

 

[SnowRidge]

If all the other hydraulic functions work fine, it sounds like it is not an engine power problem, but just in case it is, can you confirm that you have the throttle wide open and that the engine does not lose RPM when you attempt to tram (move) forward or backwards?

Assuming that the engine is not bogging, it must be a problem in the tramming circuit. I would suspect either a partially blocked filter, air in the system, or a bad drive pump.

Another possibility is a problem with the tramming control (pedal, lines) itself, but that seems less likely since it will work when warmed up.

The first thing I would suggest is to look at the control on the tram (drive) pump and see if the pedal movement is being transferred to the pump control valve. That will be difficult if you have no experience in what it should look like.

The second thing would be to bleed any air out of the tramming circuit. You should have received a bleeder hose with the unit. The instructions are in the manual, but you said you didn't get that.

Frankly, I would suggest waiting until next week when PT is back. If you don't have a pressing need for the machine, that might be the best approach.

I'm sure others will post to this thread, and perhaps someone with a similarly configured PT-425 can provide advice that is more specific to your machine.

Welcome to the group, good luck, and keep us posted.

 

[Bob999]

In addition to the items listed you might check out this thread:

Sedgewood thread

Your problem sounds similar to the symptoms that John Coxon describes near the end of the thread.

 

[SnowRidge]

<font color="red"> Your problem sounds similar to the symptoms that John Coxon describes near the end of the thread. </font>

ca 965, John Coxon = Sedgewood, just in case you weren't aware of that.

Bob999, Sedgewood has a PT-1845, which is a different beast.

According to my plumbing diagram, the PT-425's tramming circuit doesn't interconnect to the RPS valve, so that thread shouldn't apply.

Can anyone with a new PT-425 confirm that this is still true?

 

[Bob999]

<font color="red"> Bob999, Sedgewood has a PT-1845, which is a different beast. According to my plumbing diagram, the PT-425's tramming circuit doesn't interconnect to the RPS valve, so that thread shouldn't apply.
</font>

On the drawings for the 1845 the RPS valve is shown as part of the Power TAke Off Circuit. It is not shown as part of the wheel motor circuit. I THINK that this is simply an artifact of the way PT does its drawings and does not indicate that the circuits do not interact.

 

[SnowRidge]

He mentions draft control in that thread. I know what it is on a 3ph (have it on my Branson), but I have no clue what it does on the bigger PTs. From reading the thread, it sounds like it was involved somehow.

From looking at my own PT-425 and the hydraulic diagrams in the manual, I have come to the conclusion that the PT-425 RPS assembly provides pressure relief (bypass) for the two rear pumps (PTO and steering) and on/off control (PTO only) services.

The variable volume drive pump has its own internal bypass, as far as I know, and doesn't need the service of an external bypass.

The PT-425 RPS has only two physical bypass valve bodies, so it would make sense that it could only handle two circuits (pumps). It has five ports to do this--two input, two output, and one return to handle the bypassed fluid.

I still don't think the Sedgewood thread applies to ca956's problem--unless his new PT-425 has a different RPS assembly.

But I have been wrong............. /forums/images/graemlins/grin.gif

 

[Bob999]

<font color="red"> He mentions draft control in that thread </font>

If you look at Blackwell's comments in the thread he says that a problem in the valve may result in tramming problems--in addition to draft control and brake release. He further talks about the ball in the valve moving back and forth depending on whether you are going forward or in reverse. It was these comments that lead me to suggest that the thread might be relevant.

Further John Coxon talks about having problems with " a tram pedal that acts like it has a sticking cable".

 

[MossRoad]

Welcome to TBN.

A few questions:

Are you running it at full throttle?
When you attempt to move up a hill are you pushing the treadle pedal all the way down?

 

[SnowRidge]

<font color="red"> If you look at Blackwell's comments in the thread he says that a problem in the valve may result in tramming problems--in addition to draft control and brake release. He further talks about the ball in the valve moving back and forth depending on whether you are going forward or in reverse. It was these comments that lead me to suggest that the thread might be relevant.

Further John Coxon talks about having problems with " a tram pedal that acts like it has a sticking cable". </font>

I agree that he said all that, but I can't see any physical connections between the RPS assembly and any part of the drive system on my PT-425.

Looking at the RPS assembly in the photo, it is different than that on my PT-425. Also, by careful reading of his thread, I think Sedgewood is saying that the draft control is sticking. I believe he means the machine accelerates when the draft control starts working again (after the ball unsticks itself) and the draft control raises the blade from direct contact with the ground (I looked up draft control on the big PTs, so now I have an appreciation of what it is used for). I expect that would feel like a sticky cable letting go.

Unless ca956's PT-425 has a different RPS assembly than mine, I still don't see how it could be responsible for his drive problems.

 

[Bob999]

<font color="red"> I agree that he said all that, but I can't see any physical connections between the RPS assembly and any part of the drive system on my PT-425. </font>

I accept your statement. I also said that the documentation for the 1845 doesn't show a physical connection with the drive system (except a common return tank). However, the SYMPTOMS in this post sound very similar and that was the basis of my post along with comments from both Blackwell and John Coxon suggesting that tramming problems could occur from a problem in the valve.

I wonder what RPS stands for. I have never found a definition in the documentation. The documentation for the 1845 shows that is used for the PTO circuit--perhaps that is the "P". The 1845 documentation also shows it connected to the steering circuit--perhaps that is the "S". Blackwell talks about the ball bouncing back and forth when the machine is reversed--perhaps that is the "R".