MF4270 power shuttle won’t move when idling

4

4270

New member
Hello all I’m new here and come across this forum when looking for answers!
4270 24x24 power shuttle won’t move when at low revs. Also the Rev counter stopped working about the same time.
I’ve changed backend oil and all the filters and put in a new engine speed sensor.

Should there be 12v at the socket on the tractor, where Rev sensor plugs in.
I’ve checked the fuses as well, all seems ok there!
Thanks
 
Welcome to the forum.
Not sure if the rev counter is related.
Are there any lights blinking on the dash? A blinking sequence could tell you the problem.
Did you use proper fluids?
Did you check all the linkages?
Are there any unusual smells? Your clutch may be bad. :(
Is there a switch under the pedal? If that went bad, it wouldn't move at any RPM's so if your tractor runs at higher revs, this may not be the issue.
 
First off, I don't think this is the right site for you. Major traffic here is ATV's not tractors.

That said, your two symptoms are probably unrelated. The tach sensor most likely works on magnetic impulses generated by gear teeth passing near a wire coil so it will never see 12 volts from the tractor system. No drive at low idle (in both directions I assume?) could be a sign of little or no pressure the shuttle clutch(s) at that RPM. I can understand the "what" here, but have no clue as to the "why". I'm not at all familiar with that model, so I have no actual advice for you other than my guess is the problem is more hydraulic than electrical. I would start by determining if there are any other hydraulic functions that are suddenly different or affected. Steering, lift, remotes, etc.
 
Fedup said:
First off, I don't think this is the right site for you. Major traffic here is ATV's not tractors.
Click to expand...
Although most of our traffic is related to the Kubota RTV in particular, this is a tractor forum. ;)

Although your tractor is a model made for Europe, I'm betting similar models sold around the world may have similar issues.

If you don't have one already, I'd suggest you get a shop manual for your tractor as it should help you diagnose the problem.

Found this one. It appears to be free to download.
 
Fedup said:
First off, I don't think this is the right site for you. Major traffic here is ATV's not tractors.

That said, your two symptoms are probably unrelated. The tach sensor most likely works on magnetic impulses generated by gear teeth passing near a wire coil so it will never see 12 volts from the tractor system. No drive at low idle (in both directions I assume?) could be a sign of little or no pressure the shuttle clutch(s) at that RPM. I can understand the "what" here, but have no clue as to the "why". I'm not at all familiar with that model, so I have no actual advice for you other than my guess is the problem is more hydraulic than electrical. I would start by determining if there are any other hydraulic functions that are suddenly different or affected. Steering, lift, remotes, etc.
Click to expand...


Thanks for reply Fedup

Yes, both directions same symptoms.
When the RPM sensor is disconnected the tractor doesn’t move at all!!
All other hydraulic functions are fine.
The sensor is worked by a gear passing around it at back of hydraulic pump.
Do you know how these sensors work?
Does it act like a resistor and the faster the gear turns around it, the least resistance and more voltage goes to the rev counter??
 
bczoom said:
Although most of our traffic is related to the Kubota RTV in particular, this is a tractor forum. ;)

Although your tractor is a model made for Europe, I'm betting similar models sold around the world may have similar issues.

If you don't have one already, I'd suggest you get a shop manual for your tractor as it should help you diagnose the problem.

Found this one. It appears to be free to download.
Click to expand...
Thanks bczoom👍
 
The sensor is involved in that the computer monitors engine RPM, ground speed, and probably other internal shafts and gears to compare input and output. Based on that it decides whether or not to engage the transmission, and also to modulate clutch engagement. My impression was the tractor will move at higher engine RPM, but not at low idle. Is that correct or not? These computer controlled tractors have different "rules of engagement" so to speak, not all of them operate the same way. Just guessing here, I would expect if the low RPM signal were the actual cause, the computer would default to neutral and you should get some indication of that. You didn't mention that so I assumed it wasn't part of the equation.
 
That’s my understanding also fedup, though it’s not a modern tractor 22 yrs old!
It stays in neutral (stops moving) when you try to move at low revs and sometimes goes into neutral.
There is no indication on the dash your in neutral.
Slightly newer machines would have R N F on the dash as an indication you were in neutral forward or reverse, I can assume it’s either in neutral or the clutch is not engaging
Also when the tractor is reved a bit the rev counter moves up slightly.
Same was happening with old sensor!
 
So the tach registers "something" (not necessarily accurately) and then the tractor moves? When it does move how does the shuttle react? If you shift from forward to reverse and back does it change direction smoothly like it should or what happens? If a speed sensor is the problem it should throw the clutch calibrations way off and the shift should be out of whack.
 
Shifts as normal, just needs that extra bit of extra rev.
While I wouldn’t be concerned about the rev counter, I think I need to get it working first to eliminate that it’s causing the problem with the shuttle.
I’m tempted to join sensor wires together, but afraid of damaging something else!!
 
That won't help. The sensor generates a signal which is fed into the system. Joining the wires together will only confuse the issue. I agree that getting it to read properly is probably the next logical step. I don't know the tractor so I can't tell you if the computer is reading from the sensor or from the gauge. Most likely the gauge since replacing the sensor was no help.
 
Do those type sensor need voltage to work or does the sensor generate the signal.
I’ve been told the sensor should have a resistance of about 450 ohms
 
Typically there are only two wires involved. The sensor is basically a coil of wire wound around a core. As a gear tooth passes in close proximity to that core it creates a small charge in the coil which is transmitted through those two wires. No outside voltage is needed for that. What happens on the other end of those two wires is a different matter.
 
Fedup said:
Typically there are only two wires involved. The sensor is basically a coil of wire wound around a core. As a gear tooth passes in close proximity to that core it creates a small charge in the coil which is transmitted through those two wires. No outside voltage is needed for that. What happens on the other end of those two wires is a different matter.
Click to expand...

Ok
It’s like a mini dynamo or alternator.
The coil, r the core must give the 450ohm resistance!
I’ll put the multimeter on the sensor wires with the tractor at different revs and see what happens.
I’ll keep ya posted
Cheers
 
4270 said:
Ok
It’s like a mini dynamo or alternator.
The coil, r the core must give the 450ohm resistance!
I’ll put the multimeter on the sensor wires with the tractor at different revs and see what happens.
I’ll keep ya posted
Cheers
Click to expand...


Fedup said:
Typically there are only two wires involved. The sensor is basically a coil of wire wound around a core. As a gear tooth passes in close proximity to that core it creates a small charge in the coil which is transmitted through those two wires. No outside voltage is needed for that. What happens on the other end of those two wires is a different matter.
Click to expand...

I put the multimeter on the ‘sensor’.
At idle less than 1v ac, it went up erratically to about 2.2v ac at about 1/4 rev, and didn’t increase after that! I’m using an old analog multimeter so that’s why my readings are abouts!!
This convinced me that the problem was the exciter wheel, as it’s called (a gear that passes within less than 1mm of the sensor).
Back wheel of, hydraulic pump of and few other bits of and sure enough exciter wheel is loose!


Thanks Fedup for explaining how those sensors worked, that put me in the right direction
Keep ya posted
 
4270 said:
I put the multimeter on the ‘sensor’.
At idle less than 1v ac, it went up erratically to about 2.2v ac at about 1/4 rev, and didn’t increase after that! I’m using an old analog multimeter so that’s why my readings are abouts!!
This convinced me that the problem was the exciter wheel, as it’s called (a gear that passes within less than 1mm of the sensor).
Back wheel of, hydraulic pump of and few other bits of and sure enough exciter wheel is loose!


Thanks Fedup for explaining how those sensors worked, that put me in the right direction
Keep ya posted
Click to expand...
I’m interested in the voltage it will put out when exciter wheel is fixed!
 
That's interesting. Where is this exciter wheel? Most engine speed sensors read from one of the timing gears or the flywheel ring gear. I'm not very familiar with 1000 series Perkins engines.
 
Fedup said:
That's interesting. Where is this exciter wheel? Most engine speed sensors read from one of the timing gears or the flywheel ring gear. I'm not very familiar with 1000 series Perkins engines.
Click to expand...
It’s on the shaft that drives the external hydraulic pump, in the housing that the pump is bolted onto.
At the backend of the tractor.
PTO , road speed and engine speed sensors are all at the backend!
 
Got it sorted.
The loose ‘exciter wheel’ was the problem. A spot of weld to hold the wheel on the shaft. Hopefully it lasts.
Tractor is shifting and engaging the clutch perfect now.
The sensor is giving out a voltage ranging from 2Vac at idle to 8Vac at 3/4 rev!
Before it was below 1v at idle and didn’t cross 2.2v.
 

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