hesitation when accelerating

I have an 87 toyota pick up, 2wd, carbeurated 22R engine, automatic. Recently it has developed a hesitation problem when initially stepping on the accelerator, especially from a complete stop. This has resulted in stalls. I suspect the accelerator pump, but I am not sure. What are your opinions? If it is the acc pump, is it located directly on top of the carbeurator? How do I adjust it?