LX178 quits/won't run until cool

thornfield · Apr 19, 2010

My LX178 starts fine, runs for 5, 10 maybe even 50 minutes and then stops as if out of gas. It won't restart unless full choke - then maybe runs intermittently and dies. If it cools down for an hour I can repeat the process over again...
I have a new (last year) dealer installed carb, I've checked the gas cap, blown the fuel lines and even blown a bit of air thru the carb after removing the float bowl. The fuel is new, the fuel filter is new and the tank is clean. Any ideas? Thanks.

RandyT · Apr 22, 2010

I'm not sure if that engine has the anti afterfire solenoid on the carb or not, but if it does that may be the problem

rayikeo2 · Apr 28, 2010

When my LX279 was doing the exact same thing it was the gas cap. New ones are pretty cheap. If that is what it is you can tell by trying to remove the gas cap as soon as it dies. If it is bad it will be very hard to unscrew until the vaccum is released. Once the vaccum is released it will start and run another 1/2 hour and die again.
Here is the bigger problem if the cap is plugged the extra force on the fuel pump to work will destroy the fuel pump. Then you will have to buy both the cap and the fuel pump. Don't know how you tested the cap but for less than $10 you can get a new one and be sure it's good.
It is probably not a hot engine problem but a strong vaccum in the gas tank problem, the fuel pump can not overcome the vaccum to pump fuel to the carb and restricts fuel flow so much the engine dies. After your "cool down" period the vaccum releases and the pump can work until the vacc builds back up.

bruno812 · Jul 5, 2010

Did you every figure out your problem?? I have the same problem with my LX188 17 hp water cooled Kaw engine and have not been able to figure it out either.

I really think it has to be electrical but like you say it will start with full choke but die it you try to engage the deck.

Here is what i am going to try next. When it dies and it starts up will full choke. I was told maybe it was just running on one cylinder and to pull one plug and see which side its running on and then check to see if you have power to the coil, then see if its firing the plug.

I put a fuel pressure guage and i have about 5-6 oz on it.

rayikeo2 · Jul 5, 2010

Another thing to look for: If it will run with the choke on 1/2 to full but dies if you release the choke it could be an electrical problem. Look for a broken or chewed wire between the dash and the starter. You might have to remove the battery to find it. I know it sounds more like a fuel problem and unrelated to electrical wireing. A mouse or rat got under my hood and chewed several wires, one had a broken copper wire but the insulation was still keeping it togather and looking like it was not broken. Get a flashlight to check with and maybe a mirror will help.
I think the wires go through the starter terminals and then have an effect on the gas shutoff on the front of the carb which in turn shuts off the fuel to the carb.

bruno812 · Jul 6, 2010

rayikeo2 said:
I think the wires go through the starter terminals and then have an effect on the gas shutoff on the front of the carb which in turn shuts off the fuel to the carb.

The fuel shutoff was the first thing i took out of service and it still dies.

rayikeo2 · Jul 6, 2010

bruno812 said:
The fuel shutoff was the first thing i took out of service and it still dies.

Maybe the connection affects the electronic ignition, I am not sure where the link is but a broken wire in that area can cause the problem of not running. It happened to my 17 hp Kawaski engine on a Lx279. One broken wire was hooked to the bottom of the starter and another was under the battery where I could not see it without removing the battery first. I now park the mower in a mouse free area.