02 7.3 starting and stalling

[smokelvr]

just had new injectors installed. truck has extended crank after it sits overnight. oil is down 3 inches in reservoir for high pressure oil pump. one guy says oil pump is worn out and oil is leaking down through it. another guy says there is a check valve in engine and oil is leeking down there. engine has 310.000 miles. once it starts and clears out, it runs good. any ideas who is right? thanks