Ford f150 got dirty fuel. How can i flush the fuel lines?

You need to drain the fuel tank or pump it out if there is no drain plug. Then disconnect the fuel line from the fuel rail. Turn on the ignition and let the pump flush the fuel lines. You may have to do this many times to get all the fuel out as the pump will stop after about 5 seconds because the engine will not start. Now reconnect fuel line and replace the fuel filter if it has an external filter. Pour in about 5 gallons of fresh fuel and drive to a service station and fill it up. Add one can of Seafoam fuel system cleaner to that full tank of fuel. You can buy the Seafoam at Walmart or any auto parts store.

Detach the fuel line and bypass the fuel pump relay and pump it out.

Flush it like you'd flush a piece of s hit that just won't flush in the toilet.