83 mer 40 hp with runablity problem. fuel?

[mltrump]

The motor has been sitting for 10 years, but it seem to have the same problem since it was new. Will run great first thing in the morning, but after it gets later in the day it will slowly loose power and quit. After it quits you can remove the fuel line from the tank to the engine and open the throtle and will start and run until all the fuel is spent in the engine. If you reconnect the fuel line the problem will come back. Has new tank, new fuel, new fuel lines, correct fuel/oil ratio, new plugs, new wires. After taking the fuel line loose several times you can get it to run, but not at idle. Is it a fuel problem or ing. problem? possible coil?

 

[CharlieB]

Re: 83 mer 40 hp with runablity problem. fuel?

Typical symptoms of forgetting to open the fuel tank vent screw.

Runs fine until it uses enough fuel that the fuel pump pulls a vacuum on the tank, enough that the fuel pump is unable to pump any more fuel until the vacuum is released.

Try loosening the fuel tank cap and inspecting the cap vent to ensure that it is not plugged.

Another possibility is the fuel fitting on the motor, may have a defective check valve, that intermittently seals and fails to allow fuel into the engine. Or the fuel line between this fitting and the fuel pump could have an internal tear, a small 'flap' folds over and seals off fuel flow.