MT225s RPM surge

[farmiguy]

I am a new member to the forum but I have enjoyed following it for some time and finally decided to join.
I do have an issue with an LS MT225s that I bought new about a year ago. The manual calls it irregular RPM. It presently has an LS front snowblower attached and when the MM PTO is turned on there is the usual lug down but as it returns up to speed the engine speed rises and falls by 80-100 RPM’s up and down up and down… It can also occur when the tractor goes over a bump or the bucket (when attached)
hits the ground with some force. Usually by idling it back and bringing it up slowly I can correct this irregular RPM surging. Any thoughts?

Specs:
Engine: Yanmar (Tier 4) 24.7 HP IDI, No DPF Model # 3TNV80F-ZXKLST

Dealer tried a new electronic governor sensor without success. I understand it can be installed with or without a shim, not sure what that means. Dealer does not think it is a fuel issue. I use PS (white bottle) below freezing (no gelling).

Thanks for any input

 

[GS650GL]

The MT225S sometimes had governor issues that caused rpm surging. If that is what is causing yours, the only fix is to replace the injection pump. Covered under 2 year warranty. I thought maybe Yanmar had that problem figured out by now but apparently not. Yanmar still won't fix the glow plugs not staying on long enough either. I had to modify wiring so I can operate the glow plugs manually with the key switch like a MT125.

 

[farmiguy]

Thanks for the quick response. I will pass this info on to the dealer. I agree with glow plugs not on long enough. I have found that cycling glow plugs 3 times quickly to help cold weather starts. thanks again.

 

[brewdog]

Thanks for the quick response. I will pass this info on to the dealer. I agree with glow plugs not on long enough. I have found that cycling glow plugs 3 times quickly to help cold weather starts. thanks again.

I also cycle the glow plugs in both of my tractors 2 or 3 times in cold weather. I've been doing this for years and never had a problem.

 

[farmiguy]

Glad you have also had good luck when using multiple cycles. I hope it works today because the temp started at -20 degrees F this morning and we are expecting 6" of snow today.

 

[farmiguy]

Irregular RPM issue still persists. They got information from a tech rep that it maybe the wiring harness. has anyone heard of this being a possible fix? They got approval to replace the injector pump back in Feb. but appears they want to try this fix first!! The problem does occur more in colder weather (below freezing) which I am told is a symptom of a bad harness. Tractor shows no error codes. Thoughts?

 

[GS650GL]

How could a harness possibly be related to the cold weather? Not possible. Sounds like someone making up a BS story. If the speed sensor has already been tried, then the governor is bad. Throttle control has an electronic module on the back of the pump controlled by an ECU on the firewall, but the governor is still mechanical like in the old days. Pump needs to be replaced as originally posted in Jan. If they got approval to replace it in Feb. they just wasted 2 months time, what are they waiting for? Especially when it is a known issue on this model. That's why they got approval. My dealer had 3 of them with this problem, so other dealers have had them too but there is no service bulletin. Could have been fixed already but they're dragging their feet which is ridiculous. (Unless the pump is backordered, which it is not.) If they are scared because of the price (over $2700 dealer cost), remind them it is warranty and they are already approved to replace it. Their LS service rep has to give them a FFR number to approve any parts over $1500 before the repair, so they are good to go. Time is money.

 

[farmiguy]

Thanks again for your input. I will be having a discussion with my dealer. The MT225s is already in the shop for the "harness" to be replaced.

 

[GS650GL]

Good luck with that, it will be another waste of time. There would be fault codes if it was electrical.

 

[Asteral]

As a tech who works on the more technical side of things with LS, if the harness failed or was not preforming like it should 1) weather isn't going to effect the harness functionality, and 2) it would most definitely have issued codes through the CPU and while they may not show up on the dash readout they would still be there, tell them to hook up their evci tool and pull your code history and see what failure is has registered in its history log, those codes may not be active on the dash until the problem occurs and then once its running it could be storing them direct to history, I've had this happen several times, have them look for a codes in the history that have the most occurrences and have them check how often it is occurring, this should allow them to be able to pinpoint what is happening.

 

[farmiguy]

As a tech who works on the more technical side of things with LS, if the harness failed or was not preforming like it should 1) weather isn't going to effect the harness functionality, and 2) it would most definitely have issued codes through the CPU and while they may not show up on the dash readout they would still be there, tell them to hook up their evci tool and pull your code history and see what failure is has registered in its history log, those codes may not be active on the dash until the problem occurs and then once its running it could be storing them direct to history, I've had this happen several times, have them look for a codes in the history that have the most occurrences and have them check how often it is occurring, this should allow them to be able to pinpoint what is happening.

Thanks for your reply. The tractor was returned about 3 weeks ago and has been running fine. However it does not mean the problem is corrected as the RPM surge occurs more often at below freezing temperatures. Thus I will have to wait until late November for more accurate results. I hope we have colder weather early this year as the warranty expires in late December. I was told by the dealer that this model (MT225s) has limited diagnostic code features. The idea to replace the harness vs the injector pump was that of an LS tech from Canada, he told my dealer he had seen this problem many times (in freezing conditions) and a new harness was the solve. I understand that the replacement process required a large tear down of the tractor including removing the entire cab.