Try this but do it carefully.
If you have an air compressor.
Take blowgun, wrap a rag around the gun and stick it in the filler hole. Add air. the vent will let it out, but you only need about 10 PSI to lift fuel. See if you can get it running that way. You may have got a chunk of crap in a check valve.
Use caution and don't have any open flames near by this will push alot of vapour out of the tank.