I couldn't get my 1997 dodge 1500 to start so I changed the spark plugs and checked all fuses and relays then someone told me to take a mallet and bang on the gas tank which helped but now it only starts if I bang on the gas tank is it the fuel pump or filter ???

this is not something that you'll find in the owner's manual, Sounds like a bad ground and the mallet business is helping the connection to ground...could be the fuel pump, but would continuously run when the key is turned to pressurize the fuel rail...would take a look at system ground to be sure the battery is newer than 7 years old, the chassis has good ground (clean connection, free of corrosion) and to the motor block. your problem seems to be lack of proper grounding~

are you in Hawaii?

Some fuel pumps have a safety circuit that shuts the pump off when a float goes low so it won't burn itself up. Apparently that float is gas logged and sunk.by beating the tank that makes the float jump off the bottom and reastablishes a electrical feed.