2010 RTV 500 repairs

[Nicksacco]

Well , you've already done a lot of investigation thats for sure!

The erratic spark is concerning. In the old days, the disributor weights/ springs usually would stick or something. Or a vacuum dist would have a leak. Worse thing might be worn drive gears to the dist

Translate to today and you've got crank position sensor and ecu telling when to fire the plugs. And other sensors for fuel mixture and such.

Is starting hard? Does it start right away when warm or cold?

You removed the charcoal canister right?
So it was running crappy when you got the machine right?
If so that kinda negates my thoughts on that change affecting it.

It would be a shame to have to pull an engine to replace a sensor. Are you sure about that?
What about wiring to each sensor. Any chafed/suspicious wires? If so maybe the sensor wires are internally corroded ( green looking wires)

 

[Nicksacco]

According to a diagram from

Kubota Tractor RTV520E 141000 Ignition Coil And Spark Plug

Shop online for OEM 141000 Ignition Coil And Spark Plug parts that fit your Kubota Tractor RTV520E, search all our OEM Parts or call at 888-458-2682

shop.kubotausa.com

This is the pickup coil - right? PN: EG673-67870

They actually DID bury this sensor inside a bell housing! Unbelievable!

 

[kmelander]

According to a diagram from

Kubota Tractor RTV520E 141000 Ignition Coil And Spark Plug

Shop online for OEM 141000 Ignition Coil And Spark Plug parts that fit your Kubota Tractor RTV520E, search all our OEM Parts or call at 888-458-2682

shop.kubotausa.com

This is the pickup coil - right? PN: EG673-67870

View attachment 134970

View attachment 134971

They actually DID bury this sensor inside a bell housing! Unbelievable!

Yes, that's the one and yes they did. The shop manual shows the removal of the undercarriage and separation of the engine from transaxle to service it. There might be guys out there who have had luck taking shortcuts splitting these apart but I typically don't do shortcuts on my 1st rodeo.

 

[kmelander]

Well , you've already done a lot of investigation thats for sure!

The erratic spark is concerning. In the old days, the disributor weights/ springs usually would stick or something. Or a vacuum dist would have a leak. Worse thing might be worn drive gears to the dist

Translate to today and you've got crank position sensor and ecu telling when to fire the plugs. And other sensors for fuel mixture and such.

Is starting hard? Does it start right away when warm or cold?

You removed the charcoal canister right?
So it was running crappy when you got the machine right?
If so that kinda negates my thoughts on that change affecting it.

It would be a shame to have to pull an engine to replace a sensor. Are you sure about that?
What about wiring to each sensor. Any chafed/suspicious wires? If so maybe the sensor wires are internally corroded ( green looking wires)

Sorry, I somehow missed this.

I did remove the entire fuel evap system. It just seemed way over complicated for the application and a possible location for a vac leak. This machine didn't run at all when I bought it. It's got somewhere around 1500 hours on the clock. It had a blown head-gasket and was pressurizing the cooling system. Once I had that repaired and back together, it will start up and idle without any problems, hot or cold. It just skips. It will even drive around relatively well, but wont let you forget there is some kind of a problem - on deceleration, mostly. I still have to put the new NGK plugs in to see if they make a difference. The plugs I put in were an Autolite cross-ref type.

 

[Nicksacco]

Had you tried running the engine with the evap system prior to removal after you repaired the head?

The evap system does allow the carb to pull additional air (albeit fuel vapors also) from the carbon tank.
I assume you simply plugged the original vac line to the carb - is that correct?

I can't tell from the diagram, but it appears that the purge is controlled mechanically (constantly) and not via the ecu. There doesn't seem to be any harness or such in the evap system.

I was wondering if plugging off the purge on the carb would cause the engine to run richer.

 

[Nicksacco]

Had you tried running the engine with the evap system prior to removal after you repaired the head?

The evap system does allow the carb to pull additional air (albeit fuel vapors also) from the carbon tank.
I assume you simply plugged the original vac line to the carb - is that correct?

I can't tell from the diagram, but it appears that the purge is controlled mechanically (constantly) and not via the ecu. There doesn't seem to be any harness or such in the evap system.

I was wondering if plugging off the purge on the carb would cause the engine to run richer.

 

[kmelander]

Had you tried running the engine with the evap system prior to removal after you repaired the head?

The evap system does allow the carb to pull additional air (albeit fuel vapors also) from the carbon tank.
I assume you simply plugged the original vac line to the carb - is that correct?

I can't tell from the diagram, but it appears that the purge is controlled mechanically (constantly) and not via the ecu. There doesn't seem to be any harness or such in the evap system.

I was wondering if plugging off the purge on the carb would cause the engine to run richer.

Good morning,

Yes, I had run the engine prior to removing the evap system and yes, after deletion, I capped the port at the throttle body. It didn't seem to make the engine run any worse by deleting it. I actually removed it in hopes it would improve or eliminate the issue. I believe you are correct, it appears to be mechanical and controlled by a small, special purpose check valve which uses pressure above atmospheric in the fuel tank to signal a purge cycle.

All the things I've done so far chasing this issue has improved the run quality but not resolved the misfire problem. Also, after replacing the ecu, the small ecu cooling fan began working. At least is started running the test cycle at start-up as the manual stated it should. Prior to that, it had never energized.

One thing it has always done, and I noticed it immediately when I first started it after repairing the head gasket, was the fluttering throttle blade, caused by the engine governor. It appears to be cycling rapidly between fully open and fully closed regardless of engine speed or load. I'm assuming its from the misfire. If I manually stabilize it by hand, which takes more force that I initially expected, it doesn't change the run quality, only upsets the engine speed initially. Upon opening the throttle slightly further, it runs the same.

At the moment, I'm leaning towards an ignition problem. I'm certain the engine is running rich but I'm thinking the ignition issue may be causing the excessive rich condition. I guess I'm assuming these things were fuel mapped slightly rich out of the factory to begin with. Adding an ignition issue would only make it worse. The one additional test I'd like to perform is an oscilloscope reading directly on the crank sensor when running. If I can confirm it's functioning correctly, I'll be further convinced that the aftermarket ecu will be the correct path. If it fails, I suppose I'll be prepping for a large tear-down to repair it.

As I mentioned previously, if the engine has to come out of the machine, Ill be doing some extra work prepping it for the aftermarket ecu, regardless. Probably fitting a crank trigger wheel and an O2 sensor bung at a minimum.

Another interesting fact about this issue: The ecu does not recognize that there is a problem. It has a diagnostic feature that is referenced in the documentation with 3 or 4 "idiot" lights on the dash. They all light up on key, and extinguish when running. That said, I'm not sure what logic it could use to identify this type of fault condition. The only relevant input is engine speed.

Thanks again for joining me on this journey. I'm actually considering a YT series dedicated to it, especially if I have to go the way of the aftermarket ecu.

 

[Nicksacco]

Yikes! I'm out of ideas.
Curious to know about your findings using the oscilloscope.
I've never done that.
I hope you'll post again once you get the issue(s) identified.

 

[kmelander]

Yikes! I'm out of ideas.
Curious to know about your findings using the oscilloscope.
I've never done that.
I hope you'll post again once you get the issue(s) identified.

oh yeah, ill definitely keep this thread updated as I make progress. I don't own an oscilloscope currently so, Ill have to borrow or buy one. I'm with you, nearly out of ideas. It's a unnecessarily difficult situation with the limited ability to see what the ecu is doing, unfortunately. The only unknown remaining is the ignition signal, or so I think at this point. I do believe its a good little engine and I want to believe the factory ecu is a quality logic box but I've drawn the short straw on this issue for some reason. A muti-channel oscilloscope will tell the tale because I can put an inductive pickup on the plug and probes on the crank position sensor, I think. Then I'll know what the crank is doing, and what the ecu is doing in response. I suppose I could log the map and injector signals as well and then I'd have a pretty clear picture of what is happening, which would be good data for the base tune of the new ecu possibly. I don't know what the injector fuel delivery is, so I'll have to actually test that to arrive at a figure. It would be really useful to just hook up the new ecu, parallel to the existing ecu minus the outputs, to log everything but I have to keep reminding myself that the goal here is to correct the poor run condition, as efficiently as possible. I just want to put this machine to work.

Here is another scenario that I'm weighing out. The local dealer has been really good about support. I can tell they don't like working on these models just by talking to them about it. One of the managers told me bring it in if I get stuck and they would get it corrected, whatever the issue is. He even said "it would be less than $1k" which made my spidey senses tingle for some reason. I don't know why, but it seemed like an odd statement at the time. I don't know if you have had to buy any parts for your diesel RTV, but they are quite proud of them, I've learned. Labor rates are at least $100/hr. Either he was telling me he would do me a favor, or he knew something I didn't, or both most likely. I'd probably spend more than that in parts to do the aftermarket ecu, not to mention all the hours involved. I have an innate mistrust of monster manufacturers, and I've come to learn that Kubota is a monster (large) manufacturer. There is some history that I'm aware of between this machine and the local dealer, being such a relatively small city, and it further complicates the calculation. I've unwittingly stepped into a quagmire of sorts, and a quiet resolution is desired at this point. I've always loathed politics, and I'm not very good at navigating that landscape. If I do it myself, I'm in complete control. Aftermarket ECU it is...for now. At least I'll learn something. There are plenty of advantages to the MicroSquirt ecu, primarily access and generally better (more precise) engine management, I believe. Time will tell, I suppose.

 

[Nicksacco]

Hmmm, this seems so unnecessarily difficult doesn't it?

That is an interesting offer from the dealer. Might be worth doing so as not to have to mess with it, and get it over the "finish line" - as long as he agrees "it will be fixed".

I've read a bit about the Microsquirt since I'm an OEM person generally - not that I don't believe in customizations however.

Kubota is indeed proud of their parts as I learned from both restorations (L35 and RTV1140). When it comes to components "deep inside" or such, I generally go for the Kubota OEM parts because I don't want to do it again. Sometimes I'll find the parts from salvage yards - but RTV seems pretty specialized and not as easy to find.

There are a some vendors on ebay I've used that are quite good.

Muffsmotorsports
Usedcycleparts

Maybe others on here can recommend other places.

 

[kmelander]

Hmmm, this seems so unnecessarily difficult doesn't it?

That is an interesting offer from the dealer. Might be worth doing so as not to have to mess with it, and get it over the "finish line" - as long as he agrees "it will be fixed".

I've read a bit about the Microsquirt since I'm an OEM person generally - not that I don't believe in customizations however.

Kubota is indeed proud of their parts as I learned from both restorations (L35 and RTV1140). When it comes to components "deep inside" or such, I generally go for the Kubota OEM parts because I don't want to do it again. Sometimes I'll find the parts from salvage yards - but RTV seems pretty specialized and not as easy to find.

There are a some vendors on ebay I've used that are quite good.

Muffsmotorsports
Usedcycleparts

Maybe others on here can recommend other places.

Yes! All the used parts I bought were from Muffs. Excellent vendor. 110% positive feedback from me.

I hear you on the dealer service, but my gut keeps telling me I will regret it. I'm long past naive enough to imagine a positive outcome. I know, "glass half empty" and all that. If the situation/relationship were less involved, I certainly would do it without hesitation. I cant really talk about specifics, but there are several factors that present a risk and disadvantage on my side of the table unfortunately. Like I said, unwittingly stepped into a quagmire. I was naive about that. I just saw what I thought was a good deal without thinking it through. In an effort to protect all parties, and especially my wallet, I'm on my own with this one. With the exception of help from you and other members on this forum. Thanks again for that. i really do think it's the crank sensor or the flywheel. It has to be. And as much as a PITA it will be to fix it, it's just a little side by side machine. I just have to do it. At least it's not a 1 ton truck or 50 HP tractor.

 

[PoTreeBoy]

Yes! All the used parts I bought were from Muffs. Excellent vendor. 110% positive feedback from me.

I hear you on the dealer service, but my gut keeps telling me I will regret it. I'm long past naive enough to imagine a positive outcome. I know, "glass half empty" and all that. If the situation/relationship were less involved, I certainly would do it without hesitation. I cant really talk about specifics, but there are several factors that present a risk and disadvantage on my side of the table unfortunately. Like I said, unwittingly stepped into a quagmire. I was naive about that. I just saw what I thought was a good deal without thinking it through. In an effort to protect all parties, and especially my wallet, I'm on my own with this one. With the exception of help from you and other members on this forum. Thanks again for that. i really do think it's the crank sensor or the flywheel. It has to be. And as much as a PITA it will be to fix it, it's just a little side by side machine. I just have to do it. At least it's not a 1 ton truck or 50 HP tractor.

I think like you. Even if the dealer makes it run right, you'll never really know what they did. And, if you have future problems, you won't have the experience and knowledge of the machine.

I like your idea of the o'scope. In the meantime, you might play with some aluminum foil to shield the leads and move nearby wiring around in case there's some inductive coupling going on.