I've been having oil pressure problems with my 98 dodge ram 1500 with a 318. at first my oil pressure gauge would read 0psi when it was warmed up and I left off the gas. but soon as I gave it a little gas it would go back up. I changed the sending unit and that didn't help. its good on oil. now when its cold and I start it I have 0psi and I give it gas and it still stays at 0psi. and its starting to get a ticking noise. does this mean my oil pump is bad? please help