I had a fuel pump put in the gas tank, since the one i had seemed to be not working. This is the system with one fuel pump in the tank only , as far as i know. I was around 20 mpg at that time, before the fuel stoped pumping. the first 10 gallons i got an average 0f 13.32 miles per gallon. the next 10 gallons i got an average of 7.35 miles per gallon. and then i put in one gallon and only got 2.5 mpg. i had replaced the mass air flow sensor a while back. did the guy put the fuel pump in right? this truck is too old for the loaner engine trouble tool that auto zone, advanced , pep boys has. is there a place other than aamco transmision that has a free loaner or do free engine scan? Do the codes need reseting? I heard that if i remove the battery cable and put the key in accesory this will reset the code, is this true. If so do i remove the battery cable, which one, first or put the key to accesory first? I was told when you replace a mass air flow sensor you do not have to relace them again, another person said when you replace a fuel pump, it is a 50/50 chance that the mass air flow sensor will go bad, which is true. If every thing was good to start with it looks like i should not have to replace anything, but not sure. sometimes i have to give it gas to start when it has been warmed up. What can i do? This is a four cylinder, 5 speed overdrive, fuel injected, 8 spark plug wire, set up. Almost 100,000 or 200,000 or 300,000 miles.

 

It sounds as if this is an older truck. You may want to trace the fuel lines when it is dry out and check for fuel leaks. Does your truck require the tank dropped to replace the pump, if so check it hard for leaks/damage. Also if it was not done when the pump was replaced change the fuel filter.