HELP! 2005 Yamaha F150 Fuel in Air Cowl

[Catfishmaster]

Motor has been idling and running rough. Took off VST and it is clean, cleaned out fuel injectors and replaced spark plugs. Motor running stronger but fuel continues to pour into air cowl from the pressure relief valve and tube. All filters have been replaced. Fuel injectors are clear and have great spray. I run only Ethanol free gas. Everything appears to be functioning properly. Please HELP. Any suggestions would be greatly appreciated!

[fairdeal]

fuel continues to pour into air cowl from the pressure relief valve and tube.

Part # 3 ?

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The needle valve isn't sealing and the VST is overfilling?

[Catfishmaster]

Took apart VST, checked float and needle by applying air and pressure to the top of it. While pushing float up it creates a solid seal. Not sure at what point the float needs to be at but seems to be perfectly level when seal is created. All pieces, needle and seat have been cleaned thoroughly and seems to be working. But still getting too much fuel or fuel pressure at VST. Any info would be great. Been messing with this for days.

[rodbolt17]

that valve is the VST air vent.
only way it can get raw fuel is from a leaking needle valve or valve seat in the VST.

[boscoe99]

Remove the vent line to the air intake system. Pump the hell out of the primer ball. Pump it until goodntite and see if it will hold pressure.

If the ball won't stay pressurized and/or if fuel is coming out of the vent line it has to be the float valve not closing. As per rodnut, valve or valve seat.

[Catfishmaster]

Thank you all! I have been fighting this issue off and on for the last few years. And could never come up with why it would intermittently occur. It seems odd that it would have this problem and then stop if it was the needle and seat. I bent the bottom of the float to put more pressure on the needle and seat to see what would happen. I Put it back together and amazingly it has stopped the gas from coming out of the vent. I have now ordered a new needle and seat. Any thoughts on why this would intermittently happen? Thank you all again for your expert advice! My family and I are able to watch the fireworks on the lake now!

[cpostis]

You may be part of the fireworks display, if you do not change that valve/seat.

After I drain the VST for any reason, I remove the fuel supply line to the tank and use a portable tank with 50:1 to fill/prime the tank until the fuel stops and the primer bulb on the portable tank line is hard. Then reconnect the fuel line from the low pressure pumps. Good way to check the float valve needle and seat.

Happy Independence Day!