There is no pump in the tank. You could be getting crud stuck to the screen on the pick-up. I found this description on alldatadiy.com:
FUEL SYSTEM DESCRIPTION
If the fuel supply system is not delivering enough fuel driveability could be greatly affected. If air is being drawn into the fuel injection system a Cranks But Will Not Run, or a Hard Start symptom could exist. If another diagnosis indicates, or if the fuel supply system is suspected of not delivering enough fuel or drawing air, the following systems should be checked:
Any air leaks or restrictions between the fuel injection pump and the fuel tank will seriously affect pump output.
Insufficient fuel in the fuel tank
Any loose fuel component connections
Any hoses and lines that are flattening when the engine is running, or have kinks that would restrict the flow of fuel
The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame.
The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.
I uploaded the procedures to check for an air leak here: Fuel system troubleshooting
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