nt765b starting problem


my licence plate says it
Dec 13, 2009
ok so our challenger has an issue that we are having problems with the c9 motor getting started if its sat for more than a day. we have had holt cat out on 4 or five different times and they have replace the check valve on the head twice, and the pump. we have also changed the oil to a lighter oil and that helped starting when its cold but only if its started daily. now if its sits for more than a day then it cranks and cranks but wont catch. even if you either it taday it took 5 different either times to get it to run. so its like it has no fuel. anyone have any insight to why a c9 cat is leaking fuel back so it wont start or if there is something else that you know of to check.. all voltages come up right also..
There is a check valve in the fuel base and a non serviceable one in the transfer pump. Only ones I know of. Leaking lines or maybe orings on injectors.