isx will not start cranking low fuel pressure

[ktbtrucking]

Hello all,

the issue I have is as follows ... truck have stalled and towed it to repair shop.
They have changed fuel filter so far truck cranks but no start. Have arrived today to the truck have an active code for low fuel pressure. connected insite is shows 16psi with key turned on it goes to 68psi when cranking and book says should be at least 100psi.
Have tried use some fluid starter it starts for a sec and stalls. I assume I have two low pressure builded. Might have clogged fuel lines. Do not see any fuel leaks at prime pump but assume it might sucks air. Any thoughts what to do next.