Portable fuel tank starting

[Donatas]

Hello everyone, happy new year!

I have a question about to starting my suzuki df5as with seperate fuel tank. When i opening air vent screws on fuel tank and motor, after motor is starting, do i need to close those screws? Ot leave it open?

[Murray]

When running vent should be open. As you draw down fuel the void that used to be fuel is replaced with air. If you run the engine with the vent closed the burnt fuel void will create a vacuum, initially causing the fuel pump to work harder and eventually starving the engine of fuel.

[Donatas]

Both vens must be open, engine and fuel tank? Becouse when i leave it both open my engine shuts down, maybe its portable fuel tank issue?

[Murray]

Not sure on that question. Whatever tank you are drawing from the vent must be open. Possibly the onboard vent is letting air into the fuel system and causing you grief? Is there a fuel shutoff valve on the engine? If so maybe turn that off? If you close the onboard tank vent does the engine run? What I’m getting at is if the engine runs fine on the portable tank(vent open) and the onboard tank vent closed then thats the way to run it. You aren’t clear, or I’m not understanding what you’re asking, the motor starts but dies out when you apply throttle? If vents aren’t an issue then it could be a portable tank issue. You give no age/condition of the portable tank so I’ll list off some ideas, crap in the tank/pickup tube, pickup tube has fallen in the tank, plugged vent, bad fuel. Open the filler cap an have a look inside.