You probably need to rebuild the carburetor. The gas tank also needs to be cleaned. The way I did it was to use a pressure washer on the inside of the tank to remove all rust and debris, let it thoroughly dry in the sun and use a gas tank sealer. A good sealer will also seal small pin holes in the tank. If you leave the tank dirty you will continue to have problems. It would also be a good idea to replace the screen on the pickup.