Kubota RTV 900x Lost power while driving

[36racin]

While out driving the utv(work machine) which has always had 22-25 mph speed capability something happened....Going along and cart instantly lost power and will not go any faster than 12-14mph now. UTV always run on flat ground, gravel and asphalt paved roads. Kubota D902 engine

Removed fuel tank and cleaned(there was actually rocks in it)
Removed fuel hose and fitting out of tank and removed rocks out fitting.
Replaced fuel filter
Replaced one fuel injector
Replaced air filters
Removed muffler to check for plugged spark arrester(none found) but ran/drove with muffler removed with no change in engine performance



After replacing the injector I am still not getting fuel to all the injectors as I believe it should be...One definitely is working correctly and will change how the engine runs when you crack the injector...The other two not so much. Bypassed the LP mechanical pump before the injector pump with an electric pump to test(tank to electric pump to injector pump). Same running condition. I'm beginning to think I didnt have a injector problem to start with and may actually a injection pump issue. Engine doesnt appear to be running up to max rpm's

Any suggestions...I dont want to throw alot of $$$$ at this machine changing parts that may not be needed. We need this machine at work but company not willing to buy us a new one at this time...

Todd

 

[5030]

There should be a small handwheel on the top of the pump, near the injection lines. Start the engine and loosen that up and allow it to run for a couple minutes. If there is any air in the system, that will expell it and the motor should run up to rated rpm. Additionally, have you checked the fluid level for the hydro lately?

 

[36racin]

There should be a small handwheel on the top of the pump, near the injection lines. Start the engine and loosen that up and allow it to run for a couple minutes. If there is any air in the system, that will expell it and the motor should run up to rated rpm. Additionally, have you checked the fluid level for the hydro lately?

i'll try to locate the handwheel you described. I havent checked the hydro oil. I wanted to fix the engine issue before diving into a full service and fixing the long list of other issues. And it's a long list...

 

[36racin]

On another note I went out today with my temp gun...started it up and started checking temps on each exhaust manifold port. Only one cylinder appears to be working. High 180 temp where others are below one hundred and probably just residual heat from the one actually working.

 

[deserteagle71]

I know a lot of these machines are programmed so that if the seat belt is not buckled then max speed will be only about 15 mph. If your machine has that circuitry, did you check to make sure it is not malfunctioning?

 

[36racin]

I know a lot of these machines are programmed so that if the seat belt is not buckled then max speed will be only about 15 mph. If your machine has that circuitry, did you check to make sure it is not malfunctioning?

We have never used the seatbelts on the machine. Not saying the function isn't there and started working all of a sudden. I'll look at it tomorrow though. Thank you for the reply....

 

[hayden]

"Rocks in the tank and fuel elbow"? Did someone put crap in your fuel tank? A sudden loss of what seems to be two out of three cylinders could easily be explained by heavy debris in the fuel. You would hope the fuel filter would catch it, but maybe not?

Have you cracked up the injector pipes one at a time while running to see if there is fuel? If your non-running cylinders show no fuel, then the issue is upstream in the injection pump or fuel supply.

Is there a way to measure fuel pressure between the lift pump and the injection pump? If you have fuel pressure there while running, then the blockage is in the injection pump. If no pressure, then the blockage is in the lift pump or other part of the supply plumbing.

I would just start at the injectors and work backwards to narrow down where the blockage is.

 

[thepumpguysc]

If ur temp gun is showing only 1 cyl is getting fuel into the engine and burning correctly, I’d say it’s time to do the other 2.??
That’s to say if the correct reading is coming from the one u replaced..
Besides, it’s the least expensive option..(inj pump)

 

[36racin]

"Rocks in the tank and fuel elbow"? Did someone put crap in your fuel tank? A sudden loss of what seems to be two out of three cylinders could easily be explained by heavy debris in the fuel. You would hope the fuel filter would catch it, but maybe not?

Have you cracked up the injector pipes one at a time while running to see if there is fuel? If your non-running cylinders show no fuel, then the issue is upstream in the injection pump or fuel supply.

Is there a way to measure fuel pressure between the lift pump and the injection pump? If you have fuel pressure there while running, then the blockage is in the injection pump. If no pressure, then the blockage is in the lift pump or other part of the supply plumbing.

I would just start at the injectors and work backwards to narrow down where the blockage is.

Yeah atleast a handful. Not pointing fingers at to how the rocks got into the tank...Could have been from fuel nozzle from our large fuel tank being dropped in the rocks and they were inside the nozzle when the unit was refueled. I've removed and cleaned the fuel tank, fuel tank fitting(had three tiny rocks inside it, purged the fuel line, replaced the fuel filter. It didn't appear to me the manual LP fuel pump was putting out enough fuel so I disconnected it and connected a 12v pump from filter straight to the injection pump. (LP pump and gasket $189 are instock locally)

If I can get it running correctly with the 12v pump I may attempt to add it into the system and get rid of the manual pump(one off engine). I can always add a pressure gauge into the system before the injection pump to see what the pressures run...That would just be hose, fittings and a gauge.

I have one new injector already installed. And appears to not be working. Only one cylinder is working from what I can tell. With unit running and cracking the injector lines, only one of the three make any kind of difference of how the machine runs(same one with good exhaust temps
. They other two do have some fuel but I'm thinking not enough pressure to make the injectors fire. At this point I'm thinking my problem is the injection pump. And as you know the Kubota pump isnt cheap($1350 not in stock locally)

I will pull the injection pump to see if anything jumps out at me like broken springs or frozen fuel rail. And go from there. And if I can find a diesel compression tester May pull injectors and check compression as well.

Thanks for all the help....Keep the suggestions coming.

Todd

 

[36racin]

If ur temp gun is showing only 1 cyl is getting fuel into the engine and burning correctly, I’d say it’s time to do the other 2.??
That’s to say if the correct reading is coming from the one u replaced..
Besides, it’s the least expensive option..(inj pump)

Good temp is coming from an old injector. New one is in a cylinder I do not believe is working and reading lowest temp which may just be residual temp off one good one. Still leaning to an injection pump issue. So I will pull it to see if theres anything obvious like broken springs or frozen fuel rail. And if I can find a diesel compression tester I may pull injectors and see what compression is on the cylinders.. New Kubota inj pump is $1350.00

Thanks for the assistance....keep the suggestions coming

Todd

 

[36racin]

Just asking...Could small rocks or dirt from inside the fuel tank make it thru the filter, LP pump and into the injection pump? I guess anything is possible. And from what I have been reading and seeing the Injection pump has some pretty tight clearances....

Has anyone used a off brand injection pump? I can pick those up for mid 400's

Todd

 

[thepumpguysc]

I can handle the pump rebuild for u.. no problem..

It sounds like the pumping plungers are in bad shape, and when u added a new injector, the pressure is probably a couple hundred psi more than your old ones and that’s why it’s not pumping. Not enough pressure to open the injector.

 

[EXPETER]

While out driving the utv(work machine) which has always had 22-25 mph speed capability something happened....Going along and cart instantly lost power and will not go any faster than 12-14mph now. UTV always run on flat ground, gravel and asphalt paved roads. Kubota D902 engine

Removed fuel tank and cleaned(there was actually rocks in it)
Removed fuel hose and fitting out of tank and removed rocks out fitting.
Replaced fuel filter
Replaced one fuel injector
Replaced air filters
Removed muffler to check for plugged spark arrester(none found) but ran/drove with muffler removed with no change in engine performance



After replacing the injector I am still not getting fuel to all the injectors as I believe it should be...One definitely is working correctly and will change how the engine runs when you crack the injector...The other two not so much. Bypassed the LP mechanical pump before the injector pump with an electric pump to test(tank to electric pump to injector pump). Same running condition. I'm beginning to think I didnt have a injector problem to start with and may actually a injection pump issue. Engine doesnt appear to be running up to max rpm's

Any suggestions...I dont want to throw alot of $$$$ at this machine changing parts that may not be needed. We need this machine at work but company not willing to buy us a new one at this time...

Todd

Had a similar problem. My power loss was gradual though. Take a look at the muffler exhaust pipe. There may be a device there whose purpose is to filter carbon deposits. If you clean it out or remove it, your MPH speed capability may increase to 22-25 mph. Mine did. Hope this helps.

 

[hayden]

With a sudden loss of fuel at two cylinders, coupled with discovery of dirt and gravel in the tank that has to have been intentionally or unintentionally introduced, it seems almost certain that the two things are related. In theory the fuel filtration would have caught it, but maybe a fist full of dirt was too much?

 

[36racin]

Update as of 6-13-25. Still having issue. Machine only running on one cylinder from what I see. It will run on one cylinder(not well). I'm leaning towards the fuel injection pump needing rebuilt or replaced. I will speak with a pump guy this coming week. Pulled pump yesterday to see if anything obvious was wrong like broken springs inside the pump....Didn't really find anything. Could be the orings inside the injectiion pump on the two cylinders not working correctly. Wish I could find a known working used unit I could try out before spending $1400 at Kubota. Don't just want to throw parts at it. Machine needs other repairs once the engine part is repaired.

On another note. I have an electric fuel pump off tank installed and using it to provide fuel instead of the mechanical one on the block. On another site I saw mention of a ignition powered on connector in the engine bay to connect the electric pump to. Anyone replace with an electric pump and know where this connector may be located? It said the connectors even matched electric pumps sold on amazon.

Keep the suggestions coming and thank you all for assisting me

Todd

 

[36racin]

With a sudden loss of fuel at two cylinders, coupled with discovery of dirt and gravel in the tank that has to have been intentionally or unintentionally introduced, it seems almost certain that the two things are related. In theory the fuel filtration would have caught it, but maybe a fist full of dirt was too much?

I agree. Not pointing a finger at anyone. But makes you wonder....I too would have thought the filter would have caught the particulates. But if it was fueled with the engine running and with the known amount of stuff I got out of the tank when I flushed it....Then maybe, just maybe something got around the filter and wrecked the mechanical fuel pump, injection pump(cylinders not working) and plugged a few injectors. I thought i had an injector problem so I replace one with a Kubota one. No change in how it ran. I now believe I am not getting sufficient fuel pressure on two cylinders to get it to fire the injectors

Thanks for the assistance,
Todd

 

[36racin]

Just a small portion of what was in tank

 

[thepumpguysc]

Wow.!! Somebody doesn’t like you..??
Yank the pump and send me all the injectors..
I’ll find the problem, if there is one..
Just click on my screen name to “start a conversation”..

 

[36racin]

Update.....It appears it was a injection pump failure. Boss gave me the ok to purchase a new one. Installed it yesterday evening. Cart is running again(kinda) I currently have two cylinders firing...The third has a leak on the injector like I didnt add a crush washer or didnt tighten it up....So I will pull it all down again to tighten or install the washer. On another note the LP fuel pump isnt working as far as I see...I have an electric connected currently with temp power. Guess I will replace the LP pump too. Then its on to a full service and repair the other known issues....

Thank everyone for the assistance. I'm sure I need more help...

Todd

 

[36racin]

Second Update.....Cart is back to running on all cylinders. I did leave the injector loose. Also replaced the LP fuel pump and gasket. which was not working either. Can those pumps be rebuilt?