86 b2000 fuel sending unit

How do I know if my sending unit is mechanical or electric? Tryna replace the old one because my fuel gauge don't work. Mahalo!

It's electric.
Here's a link with information that will aid in repair.
www.mazdatrucking.com/forum/showthread.php/1249-Fixed-Another-Fuel-Sender!

On these trucks, typically it is a defective sending unit. Some have cleaned theirs and bent the contact arm to repair. The bed can be jacked up rather than dropping the tank for these.
See http://www.mazdatrucking.com/forum/showthread.php/12984-B2200-Fuel-Sender-Replacement