Have a 18.5 hp twin and starts up good. Seems to run real good. But after 30-40 minutes if mowing it dies and won't restart til it's good and cooled down. I have changed the coil and plugs. All good gas and nothing looks dirty don't no alot about carb adjustment or anything. Any help is appreciated. Pretty handy on diy just need to know what I'm looking for and tips on making sure all adjustments are correct
An in line red spark tester would have cost 1/3 of what you have just wasted on the coil you did not need .
So now we have only the fuel system to think about.
The most common cause of these symptoms is semi-floating debris in the fuel tank forming a plug choking off the fuel supply.
When the flow stops it floats away only to be sucked back once the engine starts running again.
Easy way to confirm this by using an alternative fuel tank the instant the mower stops
If it starts fine and runs till the alternative tank is dry then time to clean your tank.
Softened fuel lines can do the same thing
It is getting fuel all the time. After it dies. I have pulled off air cleaner and cranked on it. It is pumping plenty of fuel to it from what I can tell. Even smells of gas when trying to restart
This is why I use the spark tester.
SO you could be having a valve problem
You could be having a voltage drop allowing the carb solenoid to close
However till the tests are done you could be having a lot of problems.
If I wanted to write a mower maintenance manual then I could write one for my publisher and make money on it.
Thus I have no intention of doing it here for free.
So you have basically 3 options
1) do exactly what the techs ask you to do, post the results Then follow the instructions
or
2) continue to replace random parts till eventually you replace the defective part
0r
3) sit there while every body throws their "pet problem" at you.
Next time it quits take the gas cap off for a few seconds and try starting it again, cap might have a plugged vent causing a vaccum, never know and it doesn't cost anything either
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An exhaust valve that is adjusted too tight will do that. After running a while the valve expands just enough to leak compression.
A friend's old J-D tractor did this exact same thing because an intake valve stem was varnished up and would hang the valve open when warmed up. I suggested a HEAVY dose of Marvel Mystery Oil in the fuel tank. It only stalled out a couple times after that, then cleared up and is running great now several years later.
“Lawn Tractor dies after short time, and needs cooling off before running again”
My experience only, but maybe yours too.
My experience is only with my John Deere GX345 lawn tractor. It has a mechanical
fuel pump and a siphon feed type of gas tank (under passenger seat).
The problem is not gas tank cover, filter, fuel lines, new fuel pump, or carburetor.
After figuring out what is happening…..
The carburetor is getting more and more air mixed in the fuel as it gets near shut
down from the fuel pump. Finally the lawn tractor dies when too much air is
being pumped to the carburetor.
The air is coming from the fuel pump. The air is being sucked in by the fuel pump
via the weep hole, and pumped on to the carburetor. More and more air as the
heat rises. Test if this is your problem by injecting some compressed air into the
weep hole. You will see your mower die in a short time, I bet. Pinching off the
weep hole or weep hole hose will also restore a dead mower to action again,
that has this problem. (long term weep hole plugged is not good).
Thoughts on why?:
Fuel pump aging?
New fuel pumps have poorer tolerances?
Will you get a new fuel pump that is like the old-original pump that actually worked?
Solution.
Rerouting your fuel feed will help, but not solve. Put a gravity feed on your gas tank?
No! Too dangerous for rider!
Change to a fuel pump that doesn’t inject air.
Vacuum pump or Electric pump.
Electric pump ramblings:
The new type of fuel pumps are “brushless” and have more powerful Neodymium
magnets inside. They rotate differently and depend on the fluid moving through
to lubricate them. Gasoline and diesel do well. Water or air will destroy the pump.
Which pump? The $10 type of pumps have too much pressure and operate like a
see-saw. Noisy, too. They won’t do it for you, unless you put in an in-line pressure
regulator after the pump. There is a small one for $20 or so, that is a dial-a-pressure
spring loaded “restrictor” that should work. I haven’t tried it yet. Get a pump that has an internal
regulator. They are much quieter and in the $20+ range. Prime the fuel line when
installing or when the gas tank is empty or you will burn out the pump. One more tidbit:
Fuel filter is never totally full? It is a trapped air bubble that is difficult to get rid of with the
siphon type gas tank. You can devise a way to fill it up with fuel, but only to do it again,
another time. Just leave it alone.
