RTV 500 Won't Run After Adding Gasoline

[flynad]

I am a new member, and also new to posting on a forum. I have a 2008 Kubota RTV 500 that I bought used a couple of months ago via Ebay from a seller in Shreveport, Louisiana. It has 160 hours on it. I felt comfortable buying a Kubota because of the good performance and quality of my BX-24 I have had for 3 years. I am beginning to think I was wrong.

I test drove the RTV 500 at the time of buying on a short run around the parking lot and it ran fine. I trailered it back to my home in Missouri and on the way I filled the gas tank with 91 octane. Upon arriving home I unloaded, and then took my first drive along the trail on my 55 acres. Probably less than a quarter of a mile, it sputtered and died. I got it started again by letting it sit with the ignition on (and fuel pump running) and pumping the accelerator to get gas to it once it started. I kept it running feathering the gas pedal every time it appeared to not be getting gas and on the verge of the engine stopping.

I owned a Polaris X2 500 that had acted similar with water in the gas tank. I siphoned the gas from the tank of the RTV, thinking there was water in the bottom of the tank. I checked all the gas I extracted in a glass jar for water and/or debris, found little water, and refilled the tank. Same result -- the RTV will run awhile, then (often seems to be on a hill or curve) will sputter and die. I am always able to restart as explained above.

I took it to my local Kubota dealer and spent $120 for nothing. They pulled the fuel pump and said there was debris in the filter and cleaned it, and added Seafoam. They said it would run strong, good power, but said it did still sputter a couple of times.

After getting it home, I have had the same problem. The lower the tank gets on gas, the better it runs. However, when I add gas, it is back to frequent sputtering, engine stalling -- appears to not be getting gas when it occurs.

I am wondering if the fuel cap is having any effect -- when it is removed and then replaced after adding gas? Every bit of gasoline I have put in the tank has been examined in my glass jar before putting in the tank. I had used 91 octane, but on my last try added 89 to see if it would make a difference. It did not.

I really like the RTV 500 and had wanted one for a long time, mainly on the strength of Kubota quality. At this point I am hesitant to drive it any farther than my driveway because I cannot trust it to run. It seems there must be a simple solution, but I am out of ideas. I would appreciate any help or insight you can give me!

 

[DIXIEDOG]

Do any of your fuel lines feel "squishy"? I would check the condition of the fuel lines and make sure your tank is properly venting. I wouldn't rule out a gas cap but I'm sure Kubota is pretty proud of them and it's likely not a cheap one....do you have a friend with an RTV 500 you could swap with for a few minutes to test it out?

 

[Kanook]

Try running it with the gas cap loose and see if the problem goes away. I was going to also suggest you swap the fuel filter but I can't see that as being plugged if it runs better as the gas tank empties. I don't own a 500 myself but I've had similiar problems caused by the tank not getting vented on other gas powered machines in the past. Good luck and let us know the outcome..

 

[hawkeye08]

If it has a vented cap and the cap vent is plugged, it could be sucking gas until the pump can not overcome the vacuum created. Easy to tell by loosing the cap and seeing if that fixes it. Replace cap if it does.

 

[hawkeye08]

Try running it with the gas cap loose and see if the problem goes away. I was going to also suggest you swap the fuel filter but I can't see that as being plugged if it runs better as the gas tank empties. I don't own a 500 myself but I've had similiar problems caused by the tank not getting vented on other gas powered machines in the past. Good luck and let us know the outcome..

great minds think alike.

 

[redharley]

Louisiana,I'd double check that fuel system for Water,mud,and other junk,pretty wet in that part of the country.Some body might have lost a cap run it that way for a while or used a gas can that was sitting out in the rain with no protection. sound's like a dirt or water problem. Did the place you took it to remove the tank and clean it? Mud wasp and other insect's can build nest in vent holes for sure.

 

[timswi]

Yep..Could be fuel debris....My first thought would be a form of vapor lock though. The fact that it runs better as the fuel level lowers would make this appear more likely. Not sure what new cap costs, but I'd try one. Also, there are probably vapor return lines, i'd make sure one of those isn't kinked or clogged.

Given that the RTV500 is fuel injected, it probably has evaporative controls.

Your machine is probably fine in general...just have to geet creative hunting this down....Patience. Hang in there.

 

[flynad]

I appreciate all the info. The hoses appear to be fine. I loosened the gas cap and it made no difference. The gas cap may be vented but it's not obvious---no holes---but is in good condition. The tank has been emptied twice, once by me and then more extensively by Kubota. The fuel pump according to Kubota is mounted on the bottom of the fuel tank and the only fuel filter is mounted between the tank and the fuel pump. It was cleaned by Kubota. The only gas that has been put in the tank since the tank was drained and cleaned has been first poured into a pint glass container by me and examined for dirt and water. Running it in low gear with a higher rpm greatly increases the sputtering and will cause it to die within a hundred feet or so. I think some of you are on the right track about not getting enough air. I wonder if it has another air intake rather than the gas cap? It's starving for fuel. Thanks for all of your ideas.

 

[SpudHauler]

So does that mean if you ran it at low rpm you could go a long distance.

What I'm thinking is, you checked everything to the carb, but did not have it off and cleaned. Some carbs have a small screen type filter just before the float needle and seat. Don't know how much you know about carbs, but next thing to do would be have it checked and cleaned.

Another method would be to remove the float drain plug located at the bottom of the carb, turn on you ignition or at least until the fuel pump started and see what kind of flow you are getting out the drain. If it is a trickle, the inlet needle is partially plugged with something. If the flow is strong, then it is not the fuel system and probably electrical.

Your a dealing with GAS so be careful and catch everything in a pan or something. NO SMOKING PLEASE.

 

[Stonehaller]

The fuel tank is vented through a filter canister much like automobiles. Take a look at the attached parts diagram. The canister filter may be plugged or the valve in the vent line may be clogged or not working

 

[SpudHauler]

Good one.

Or just pull the vent line off for a quick test.

 

[redharley]

If you are running out of fuel [lean condition which is BAD for your engine] your spark plug should be a dry white color.If your running out of air, plug usally dark brown to black. This thing is fuel injected, right?

 

[timswi]

It's fuel injected..no carbs or screens..2 cylinder, so check both plugs. I doubt that it's a lean condition...Sure sounds like an emissions version of vapor lock.

 

[David_Kb7uns]

Has any one checked the fuel pump pressure when cold and when hot and running? From the ATV world, weak fuel pressure is a problem that occurs often. Some EFI systems need 40-50 PSI or more to operate, debries can also jam the regulator open and lead to lean running problems.

David Kb7uns

 

[stuckinnj]

One more test you may want to think about. The vapor canister is not designed to maintain liquid. If the canister has filled with fuel, it will not vent properly or at all. That may explain why at half tank, the engine begins to run better. There should be a line from the canister to the filler neck or direct to the tank (this is how the vapor is trapped and released back into the fuel system). If the canister is full of liquid, you may need to replace. I would try to vent to atmosphere to see if it will 'dry' out. You can tell by the weight. Much lighter w/no liquid.

I believe I read you topped up the tank w/fuel before hauling it home. It is very possible all that sloshing around while hauling allowed liquid fuel to enter into the vent system. I've seen this too many times from folks topping up their fuel tanks in the morning and letting their car sit in the sun during the day. Fuel expands and in today's closed systems can only go one place - the vent system i.e. fuel canister. And yes, this will cause poor engine performance and the old check engine light to illuminate.

One more thing to think about. The fuel pump typically requires at mimum 13.0 volts to maintain operating pressure. More demand, more fuel requirement, more amperage required to maintain pump pressure. You didn't mention if you have any battery consumers on i.e. lights, radio, etc. I would suggest testing the alternator output - voltage and amperage. If the battery is marginal or alternator will not support the amperage requirement, the fuel pump will suffer. Again, may be why the engine runs well under light load / low RPMs not under heavy load / higher RPMs.

Just something else to consider.

 

[flynad]

I'll check the canister when i return home in about a week. thanks for the info===flynad

 

[flynad]

I finally returned home a few day's ago and began looking for the problem on my RTV-500. I checked everything that has been reccomended with no luck. Yesterday i took it down the road to a local auto repair shop. He thinks it's electrical. He checked the fuel pressure which was 40# up hill and downhill. The spark plugs had signs of misfiring so those were replaced and it does run smoother. He drove it around and it would never die or cutout for him. I picked it up last night and drove it home. It ran fine. I added gas since it was on a half tank. I then drove it approx. one-eigth mile and it quit. Got it re-started and made it back to the carport and it died again. Guess i'll take it back to the local mech. and let him keep it for awhile. It's about to find a new home. This is typical of buying something like this used. thanks for your help. flynad.

 

[SpudHauler]

Would it be possible to leave the fuel pressure checker hooked up and go for a spin until it quits. Perhaps the pump is quitting after it gets hot. Motors can start breaking down when hot as things expand and continuity is lost.

 

[flynad]

yes, the mechanic left the pressure gauge on it when he test drove it.

 

[Rod in Forfar]

I had an outboard motor one time which would cut out occasionally under load. It took half a season before a mechanic figured out that it was a wire too close to the fly wheel, grounding against it only when the governor advanced the spark.