96 12 Valve hard to start when cold?

[Foster#17]

My buddies 96 12 valve is hard to start when its cold. Once its been running it will fire right up! It only seems to be a problem when it sits for a while. I believe the problem is an air leak somewhere? They replaced the lift pump, and both rubber lines going to the frame. What other lines could be causing this problem??? It almost has to be an air leak.

 

[Shainer]

Fuel filter, specifically the fuel heater. Search that.

 

[95cummins5.9]

Also the overflow valve..

 

[GAmes]

An air leak could be anywhere on the suction side of the pump, starting at the fittings at the top of the tank. If you pressurize the tank with about 15psi of regulated air the source will bubble.