the black box on the left side of the trunk
The fuel pump is located in the the top of your fuel tank.
it is either you have a shor in your wiring or you have a loose connectoin or you need a new relay
5300lbs.
Yes
Yes, a person can get a diagram of the PCV valve location in a 1989-1999 Mercury Grand Marquis. This diagram would be located in the maintenance books found in auto part stores.
It may not have one but if it does of course it will be located somewhere inside the glove box.
If I understand your question correctly, your vehicle may have a separate relay for each function. The relay for locking the doors by using the switch has gone bad.
It says on the door
left side of dash
5 lug 4.5 inch
12 Gallons (US)
where is turn signal relay located at 1989 mercury sable