There is no 1991 VW Rabbit.
You can find the 1991 Nissan starter motor relay switch in the fuse box. The starter motor relay switch will be in the third column, second from the bottom.
replace starter
as with any starter motor just look for the gearbox and it will always be connected somewhere to that.
Front of the transmition
you have to take the starter out of the car and dismantle it.....it's an integral unit
underneath engine, bolted on passenger side of engine,
Pull the motor out of the car and change it.
The starter motor is located between the transmission and the engine which engages the starter clutch with the flywheel, which rotates and starts the engine.
Probably the starter, have someone turn the key to the crank position while you gently tap the starter with a hammer or bar. If it starts change the starter. If not try shorting the starter solenoid to see if that works.
Same answer as: "How do you replace a starter on a 92 Geo Prism LSI or GSI?" at this same site.
I use a starter solenoid from a 1991 - 1995 Toyota Pickup on my 1998 FLHT Evo... and a fraction of the cost from Harley.
On the driver side of car under hood. Starter sits midway of engine at the bottom part of the engine.