Need help with my 94 max

hi everyone,this is a very nice site,but could not find my answer listed,I have the 94 mighty max,2.4-5 speed,changed all fluids,tune up with new plugs,cap,rotor,fuel filter,etc,ran good for 3-4000 miles,the problem i am having is after it warms up,it starts hesitating,sputtering,and a little backfiring,i stopped and let it cool off for about 20-30 minutes,then it will start and run fine again,then warms up and does the same thing again,and is their anyway to test fuel pump without buying a new one first and where is it located at,any help will be greatly appreciated

change your ecm temp sender it is the one with 2 connections