Replace the fuel filter.
NO, the Mazda B4000 is basically a re-badged Ford Ranger. The 4.0 L engine has a timing chain and not a belt.
In the engine bay
4.0 l ford engine
The thermostat may need to be replaced.
I believe it is on the drivers side of the engine , below the power steering pump
it depends on the bolt patterns but don't c y not but if its a 4x4tranny it may not if the Mazda isn't a 4x4
It should be located on the left side of the engine (looking at the headlights), beside the exaust manifold.
www.promanuals.com/serviceparts/2004-mazda-b4000-truck-owners-manual-automated-download
The recommended spark plug gap for a 1998 Mazda B4000 is .054"
where i look only year 1994 mazda b4000 truck -fuel sending that find hard time
Instructions on how to remove a 1994 B4000 Mazda 4 wheel drive transmission
The B2500 Series Mazda pick-up has a 2.5 L engine. FYI: B2000 = 2.0 L; B2500 = 2.5 L; B3000 = 3.0 L; B4000 = 4.0 L.