Common

Is there supposed to be a flap on my fillneck?

OK, the diesel sits in the tank...

How does it get to the engine?

Map it out for me...

Does the lift pump suck it out of the tank?

Is there an actual fuel pump in the tank?

I'm sorry, I'm just confused...

bgilbert

No flap, just a screw on cap.
It gets to the engine by way of a mechanical piston type lift pump driven by the camshaft of the engine. It sucks, then spits . No fuel pump in the tank.

infidel

No flap but there is what's called a rollover ball in the fill tube. It's a little smaller than a tennis ball and is there to keep the fuel in if the truck is upside down. It also prevents a siphon tube from being inserted and you from filling up at high speed big truck pumps. It is easy to remove.

Fuel is sucked from the tank by the mechanical lift (transfer pump) on the engine block up though the fuel heater, which contains a cleanable prefilter. From the lift pump fuel flows though the fuel filter to the injection pump.