Can you boost off a 99 crown victoria battery

No they are not the same door, you would need a Crown Victoria door.

Owners Manual is on the internet

Google it

No fuse or relay will fix your issues,I doubt

keyon, very bad, and cranking very common.

battery power is weak, not 12.6v rested.
use a volt meter
or jumper cable start it.
walfart has voltmeter for $10 , the $20 Crown VIc meter ,is 20
get a cheap DMM and see.
or here.
a whopping 15 bucks and magic happens, you see the system mess up even driving. same place next o car batteries, walk in. see it.
http://www.walmart.com/ip/Equus-Innova-3721-Battery-and-Charging-System-Monitor/15137663

if the battery is good and the meter above is low, the cars wiring is bad. (corrosion does kill all old cars. )
i restore old cars, and can show this all day,..... its endless.
have lots of photos too.

that clattering is all the computers in car, (1 or 2 back when)
are going NUTS with 1/2 power appied. all modern cars do this.
and worse newer, (be happy car is not new)



Sig: I must ask questions first, I'm blind, and my tools can't reach, dig?

The battery is not the problem the starter solenoid that is mounted on the inside of the fender near the battery is causing this, the contacts get burnt from running a weak battery and burn closed. The red (+) battery cable goes to one side of the solenoid and the other side goes down to the starter. See picture below. I seen this dozens of times in my shop. The part is less than $20.00

Under the hood, remove fuse cover the main fuse will be in between the positive cable coming from the battery and a ground cable. Follow the positive cable coming from the battery to the fusebox and the fuse will be visible.

Try turning on your hazard/warning flashers. The DOT 3 fuses are usually right next to each other. Follow the clicking sound.

check the blower relay also check the ground to the heater motor as well and use a jumper wire straight from the battery to the blower motor to make sure it isnt burnt out

Use lots of wd40 on tank strap bolts. If they bigin to bind tighten them up and losen again to get rust out of threads. If you remove the straps, why not remove the fill neck and lower tank? Much easier to work that way!!!

where is the fuel pump relay on a 2001 crown vic p71

did you check the inertia switch?? that's what happened to mine