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john deere lx178 keeps cutting off

Mike Jeter I have a 1991 lx178. It starts fine but after 10 minutes running, it starts acting like it is going to cut off and eventually it does. If I turn on the mower blades, it stops sputtering and runs fine but as soon as I turn off the mower deck, it will start sputtering again and then turn off. I have to wait about 15 minutes before it will start up again and when it starts, black smoke comes out the exhaust. I replaced the air filter,spark plugs, gas filter and the gas tank cap but it still sputters and cuts off unless I turn on the mower deck. After about 1 hour of cutting grass, I checked the new plugs and they were already turning black. For $40, the dealer said it was vapor lock and replaced the part of the fuel line that runs from the shut off valve to the engine but this did not correct the problem.
Any ideas on what the problem is and how to fix it?

ponymare Are you sure the choke is coming all the way off, the extra power it takes to run the deck, may override the half on choke. You don't mention what engine, but the valves may need adjusting.
RoadRunner Just a word about Vapor lock. Back in the 1940 era some vehicles had the fuel line ran very close to the exhaust manifold. This in turn caused the gasoline to get hot and boil, causing what is called Vapor lock. The gas was changed into a vapor and would not fill the carb. The engine would run again after all got cooled down.
This problem was widely talked about, and the term Vapor lock has stayed in mind for all those years. We haven't had REAL VAPOR LOCK for years.
But for some reason people still blame vapor lock and really don't know what there talking about. When you hear that term, look for the fuel line and if it's not next to the exhaust then look for something else for the problem.

Joe Hubbard You are correct Roadrunner, I had my dad read your post, he confirmed it. Back in those days the fuel line was metal and was ran the shortest way they could run it. Todays engines use flex line which has to be run away from the exhaust to keep it from melting or burning through, causing a fire.
Mike Jeter Thanks guys for the info. I checked the fuel line the dealer replaced and it was resting against the heat shield so I rerouted it away from the heat.
I started the engine and it still sputters. I noticed that there was gasoline seeping out of the weep hole on the top side of the fuel pump so I had to shut it down. Could the sputtering cause gas to come out of the weep hole or could the fuel coming out of the weep hole be a sign that the fuel pump needs to be replaced and it is the fuel pump causing the problems? I know that if the fuel pump is going bad, it would restrict fuel to the carb but I did not think that a bad fuel pump would send too much fuel to the carb.
I am retired and try to keep the Deere running on my own but this sputtering, cutting off and fuel coming out of the weep hole has me scratching my head. It is a kawasaki 15 hp on my lx178

Thanks for any help you can give me

RoadRunner If you have fuel coming out of a air vent hole in the fuel pump, then you have a bad fuel pump.

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