I had a pulse dampener that was leaking my system pressure down, eventually it wouldn't run as it would not make 55psi. Its between the pump and the hard line and it just plugs in. the ends of it are a really tight fit, but mine was weak after 20years and the pressure blew it off and allowed leakage inside the tank. The parts houses dont sell that part for some reason. Its an AC Delco part that you only get from a dealer. Try replacing that. i don't think it comes with the sending unite either, although i could be wrong. I had to go to the Chevy parts counter to buy on. It was only 40 bucks. BTW it was the last component to be replaced. I had new spider, new regulator new sending unit/wire harness and new pump. Some people I have heard just delete the pulse dampener, as it is just one more link in the chain that can fail, and some feel its not necessary. If mine is ever out again I am going to delete it.