721 Kubota Gas engine dies

[wannablast]

Hey guys,
I've got a 1999 721 with the Kubota gas engine. The dang thing vapor locks and shuts down and won't restart until it either cools down or I remove the fuel line at the inlet side of the pump and blow into it to pressurize the tank. It then overcomes the vapor lock and will run until it does it again. I've replaced the mechanical fuel pump, the fuel cap, the draw tube, the filter and all the gas line to the carb. The carb selenoid is activating when the switch is turned on. I've even converted it to the 725 electric fuel pump with the same results. I'm about to drive it off a cliff, @ 7mph, just kidding. If anyone has anymore ideas I would appreciate it.

Thanks
JT

 

[KennyV]

Welcome to LMF...

Do you have a fuel filter on it? Is it in front or behind the fuel pump?
If it is in front of the pump... remove it and see if it still Vapor Locks... :smile:KennyV

 

[wannablast]

The filter is between the tank and the pump. I removed it the other day. The mower went from running a half hour or so to 2-3 minutes. Now I put it back on and the same thing occurs. It runs out of gas in 2-3 minutes.

 

[Black Bart]

Have you tried using air to blow back into the fuel tank maybe the outlet from the tank is blocked.
Back when I worked on cars I had a guy bring me one that would run fine and then just stop.
After it sit for awhile it would run again.

What I found was while adding some additive he lost one of those cardboard tops into the tank and it was getting sucked over the fuel outlet.

With the engine in the open I don't see how it can vapor lock.

 

[wannablast]

It used to vapor lock and die when it was about halfway up into the green operating temp range. I could run water through the radiator and it would run fine for a half hour or so. About half the time I would then get a short on one cyl from the water so I stopped doing that. Then I converted it to an electric pump like the 725 G Hopper. It cut fine for one cut and then when I was cutting the mother in law's grass it did it again after about an hour. I'll check the tank for trash. At this point it won't hurt.

JT

 

[Black Bart]

It used to vapor lock and die when it was about halfway up into the green operating temp range. I could run water through the radiator and it would run fine for a half hour or so. About half the time I would then get a short on one cyl from the water so I stopped doing that. Then I converted it to an electric pump like the 725 G Hopper. It cut fine for one cut and then when I was cutting the mother in law's grass it did it again after about an hour. I'll check the tank for trash. At this point it won't hurt.

JT

It sounds like it may be overheating if water through the radiator keeps it running.
Put a baking thermometer in the radiator and see what the temp is thermostat may be stuck.

 

[Workstead]

This is an old thread with no conclusion but I had a similar problem - run a while and then shut off. My problem was water in the gas. After trying many things, including changing the electric fuel pump, etc, etc. I emptied the gas tank and found a pint of water in it. The fuel gauge leaked around the plastic cover and the mower was parked outside. New gas solved the problem.

 

[KennyV]

This is an old thread with no conclusion but I had a similar problem - run a while and then shut off. My problem was water in the gas. After trying many things, including changing the electric fuel pump, etc, etc. I emptied the gas tank and found a pint of water in it. The fuel gauge leaked around the plastic cover and the mower was parked outside. New gas solved the problem.

WELCOME to These Forums
Plus your First post is a very helpful reminder to look for the simple solutions First.... :smile:KennyV