Good afternoon. I have a kubota rtv 500 efi that struggles to start and will puff black smoke out of the exhaust. Usually I can unplug the injector while cranking it and it will start then have to hurry and put the connector back on. At which point it will run half or full throttle but still puff black smoke. The plugs keep fouling. I suspected they may have mixed diesel into it being their older one was diesel. Drained the tank twice and filled with fresh gas. Still doing the same thing. I unplugged the map sensor and surprised it would sorta idle and run normal but still rich. Ordered a new map and the symptoms did not go away. I've disconnected the evap canister and have also searched a few different forms. Seems everyone has tried maps, ecms, iat, injector along with a list of other things but never got it fixed or didn't post it was fixed. Anyone have any experience with this? I'm going to check to see what the fuel pressure is either tomorrow or next week. Thanks
Kubota RTV 500 Black smoke hard to start
- Thread starter Flcracker13
- Start date
Maybe a few guesses based on assumption diesel was run through it.
- Check/replace fuel filter(s) - diesel will mess them up.
- Quite possibly diesel mix still in fuel system - can you use air and blow everything out? Can you disconnect everything from tank into engine fuel system and flush and drain with something like carb cleaner?
- Injectors could be clogged from diesel
- Fuel pump messed up?
GreensvilleJay
Well-known member
Equipment
BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
Check engine oil...ANY 'gassy' smell ? Proper level or over full ?
'black smoke on gas engine' usually says 'rich' mixture
? how long have you run it ? It may have 'diesel' in the muffler, may take 15-20 mins to get muffler HOT and burn off any 'oil/'fuel' left in it.
'black smoke on gas engine' usually says 'rich' mixture
? how long have you run it ? It may have 'diesel' in the muffler, may take 15-20 mins to get muffler HOT and burn off any 'oil/'fuel' left in it.
these are a map system which heavily relies on TPS and manifold pressure to 'adjust' fuel delivery.
with that said, if the map (manifold absolute pressure) is higher than it should be, it's GOING to run rich. Very rich depending on the actual map reading. Typically around 4-4.5 psi is idle speed hot and 14.5 psi key on engine off (atmospheric or very close).
So the question is, what can cause high map? Vacuum leak, leaking valve(s), cam timing, etc (these have a timing belt so keep that in mind)
If it's "that" rich, it's DUMPING fuel into the engine for some reason. Perhaps the fuel pressure is just way off, due to a stuck regulator. Also a failed engine coolant temp (ECT) sensor can cause very rich running, by default they'll go into a rich mode if the sensor is bad or the wiring leading to it is bad.
Remember too that a sensor doesn't necessarily have to be bad, it could very well be a wiring issue. The ECU wants to see a voltage on most sensors, and the wiring can cause that voltage to either not get to the ecu properly or get none at all to the ecu.
with that said, if the map (manifold absolute pressure) is higher than it should be, it's GOING to run rich. Very rich depending on the actual map reading. Typically around 4-4.5 psi is idle speed hot and 14.5 psi key on engine off (atmospheric or very close).
So the question is, what can cause high map? Vacuum leak, leaking valve(s), cam timing, etc (these have a timing belt so keep that in mind)
If it's "that" rich, it's DUMPING fuel into the engine for some reason. Perhaps the fuel pressure is just way off, due to a stuck regulator. Also a failed engine coolant temp (ECT) sensor can cause very rich running, by default they'll go into a rich mode if the sensor is bad or the wiring leading to it is bad.
Remember too that a sensor doesn't necessarily have to be bad, it could very well be a wiring issue. The ECU wants to see a voltage on most sensors, and the wiring can cause that voltage to either not get to the ecu properly or get none at all to the ecu.
I drove around our shop multiple times for 20-30 minutes thinking it did just need to burn off anything if they had mixed diesel into it or if there was any excess in the muffler.
The second time I drained it I used air to get what little bit out I couldn't get just by siphoning it. I might me possible to run it off an external source I'll have to get a pump or try pressurizing the tank to push fuel into it. Checking fuel pressure was my next step.
GreensvilleJay
Well-known member
Equipment
BX23-S,57 A-C D-14,58 A-C D-14, 57 A-C D-14,tiller,cults,Millcreek 25G spreader,
good, you've eliminated 'muffler' as the source of the 'richness'. I brought it up as I'vw seen waht happens when people turn their turn mower onto the wrong side, oil gets into muffler,the once it finally starts, yo can't see the neighbourhood for an hour ! Sounds like LB has a lot possibles for you to check out.