A friend of mine has a matching numbers 69 Dart GTS 383 4 speed car. Since he put the car away last winter,the car has had no oil pressure on start up after sitting. If he pulls the coil wire off before starting it up,and cranks it over until it shows oil pressure on the mechanical guage,then its fine until the next time it sits,then it's the same scenario. He has replaced the oil pump three times,with three new,different pumps,and it does the same thing. This summer he drove it to a few shows that were a couple hour rides,and after diving the car alot,it didn't have the problem,until it sat for the last two weeks,then after trying to fire it up again,it was knocking and clacking until he shut it off,and primed it with the coil wire off again,then it was fine. He needs help figuring this out,as the car has the matching numbers engine,and he dosen't want to hurt it. He is getting ready to drop the pan to see if there are problems with the pickup to the oil pump. Any ideas as to what else could cause the loss of prime issue,after sitting?