It rides piggy-back on the starter.
diaphragm of 1991 Nissan sentra
Disconnect the positive battery cable, and replace the starter. 2 bolts, a couple of wires , and replace it. It's just that simple.
IS IN THE DRIVER SIDE OF THE ENGINE A LITTLE TOWARD THE BACK OF THE ENGINE
The starter in a 1991 Nissan Sentra is located on the driver's side of the engine compartment. It is easily spotted down in the gap between the engine head and the air intake and battery areas... It looks like a fat cylinder at the top of the engine and transmission joining.
Ususally 2 bolts go from the engine side to the transmission and one from the transmission to the engine.
Your Nissan dealership can get one for you!
The 1991 Nissan Sentra GXE has a gas tank capacity of 13.2 gallons, and takes regular unleaded fuel. The Sentra was first produced in 1982.
Super Multiple Junction
I found mine on the back of the engine about mid way up. it was a pain to find, and i got a buddy to replace mine for me.
The starter relay can be found underneath the hood on a 1991 Nissan pickup. The starter relay is beside the battery on the passenger side.