Why does battery drain rapidly?

You could have a bad ground (earth) wire. Follow the negative battery wire until you reach the end which will be connected to the engine area. There should also be a wire that will ground the body to the engine. Go to a parts store and see if they have one so that you know what you are looking for.

Batt probly not chargn cause main wire in back of alt is wornout. Alternator tho sounds bad..it will drain a battery quik.Disconnect batt ovenite to confirm

Year make and model ?
You may have fried the engine computer by using that jumper wire.
The sensors run on a 6 or 9 vt reference voltage, not usually battery voltage. And the engine computer provides the ground side.
Did you check for vac leaks before doing what you did with the jumper wire ?

have you checked the volts to the relay for the injectors ?

Possible ECM not seeing cam or crank signal to fire injectors

the wire harness has a flaw or in a switch--u need a pro for inspection--chec for loose grounds--also disconnect alternator from batt to see any difference--good alternators can have an internal issue that drains battery

poss bad batt, cell also fuel injected so pushing gas or not no matter.

JUNK IT ITS A PIECE OF ****

most likley the positive wire has corroded off the starter. look at the small red wire more closely, if theres alot of corosion, replace the wire (and starter if needed) if you dont see much corrosion give the wire a good tug just to see if it really is hooked up well. you should disconnect the batt. before doing any of this.hope this helps and good luck

sounds like you need a new battery, it probably isnt running enought cranking amps to start your car, try a different battery and it should start fine