2001 6.6 hard start when warmed up

[smittymann]

had a problem with the 6.6, changed the fuel filer housing/primer pump & the two fuel lines on top , with a new fuel filter ,...it was great for 1 day ,nex day same problem ,..after it is warmed up & shut off its a hard restart ,..checked all connections all good & clean ,..no pressure on primer pump ,..no fuel leaks ,..its an 2001 ,with 164 k on it had new inj, installed at 121k ,..any help appreciated ,...

[More Power]

Welcome to the board!

If the problem suddenly appeared after the new fuel filter assy was installed, I'd want to positively eliminate that as a possibility before moving on.

If you can pump the primer and remove air after the truck has sat for a time, there's air getting in somewhere.

[smittymann]

the problem was there b-4 i changed the primer pump & filter assy,& the 2 fuel lines from the primer pump ,..thats why they got changed ,..funny thing was it ran perfect for 1 day ,..now its back to suckin air from somwhere ,..maybe ill have to change all the rubber fuel lines , the ones off the primer pump were cracked ,..fig between that & the primer pump i was losing the prime ,...i guess ill have to take a closer look ,...thanks for the input ,...

[Kennedy]

Put a lift pump on it and apply steady pressure to the system. If there is a leak you will find it. If not you'll still be helping the filter, injection pump and injectors.

Often it is as simple as a leaking oring on the OE filter head. Many condemn the filter head as "cracked" but I don't buy that. For $20 we have a simple oring kit that replaces all of the orings in the filter head.

WIF sensors tend to leak. We replace with a plug with a drain.

Also, the black plastic fuel filters also tend to be difficult to seal and are truly sub standard in design as hey are a single layer media vs dual layer of any good modern filter.

If bleeding/pumping do not help then it's injectors allowing excess return flow which is often mis diagnosed as a bad injection pump.