Blows fuse #116 when turn key on

On an older vehicle with a lot of miles, it is likely to be a rubbed through wire in the engine bay or the wiring harness under the steering wheel. Here is a trick. Replace the fuse. In the pitch black of night, let your eyes acclimatize to the blackness. Look in the engine bay and look for a flash as someone else turns the key.

If that doesn't work, you need a mobile auto electrician with access to the wiring diagram and the experience to test where the short to earth is..

dont know why changed fuel pump if total power failure but need to test electrical for short [ will need a meter ] start with battery test and check wiring and connections and wotk your way thru ignition system and starter system looking for reason system has a direct short

Turn key to On.
Turn on headlights manually... Do they come on?
Are there any lights on the dash?
If yes to these, battery is possibly not the sole problem.
Check for good, tight and clean connections at battery terminal posts!
If yes to above, continue on & get a helper... Turn key past on, to Start position.
Do you hear a click sound at time key is turned to Start?
If yes, then ignition switch is not problem, starter relay is getting power, and is now sending power to starter, but starter is not working.
Pic any No's... Then look there.
Good luck.

A bad short blowing the fuse. Could be in the wiring for that circuit, or bad part, component (like the computer, sometimes a shorted injector).
Check if the fuse still has power to it. Use a test light to check for power at the fuse. If no power, probably blew a fusible link or maxi fuse that is the feed for that fuse block.
Turn key to on-do the warning lights and dash gauges come on? If not, check that power is still getting to the ignition switch. I think there are fuses (AM1 &2?) for the ignition switch, not fusible links.
Shorts in the wiring can be difficult to find, may be buried deep in a wiring harness, one needs to check continuity of wiring to locate wiring shorts, looking for high resistance in a section of wire-you may need a shop to diagnose. If you have a wiring diagram available, could start checking wiring and parts in that circuit.
If you want to get creative, here is how an auto electrician can hunt for shorts: use some jumper wires and hook up a circuit breaker of same rating as the efi fuse in that fuse slot. Now when testing you will not be constantly blowing the fuse-circuit breaker will reset every time. Unhook parts in the circuit one at a time, turn key on so power is going through the circuit, whatever part is unplugged that breaker does not trip, that is the problem-the wiring to it or the part itself. Also do a wiggle test of the wiring: key on, move different parts of the wiring and harness, if you cause the short tripping the breaker (or blowing the fuse if you just keep adding a new fuse each time) then you have found the short.
Here's a heads up: anytime you want to pull the connectors off of the computer, make sure key is off, remove negative battery terminal, pull connectors off the computer, reattach the negative battery terminal. With connectors off examine connector pins for any corrosion or bent pins.
Good luck, get power back to the ignition switch if it is lost, then start looking for what is blowing the efi fuse.

A bad something, yes.
The fuse may be the primary fuse for the key switch. If it is, you would need to disconnect the key switch harness and check for a short to ground on each circuit.

Possibly a shorted injector, or a short in the wiring. Pull off all injector connectors from the injectors, put a new fuse in, and turn the key to on. If the fuse blows, look for a short in the power wire going to the injectors. If fuse doesn't blow, reconnect one injector at a time (key still on). If one of the injectors being connected blows the fuse-that is your shorted injector. Have to replace it. Good luck.

U have a positive wire making ground

This means you have a dead short, you will need to look around engine area for bad wiring or component, you will need to start disconnecting components under the hood in the engine like injectors o2 sensors alternator , my first test would be to disconnect the small wire to the starter and leave the big one one for now and see if the fuse dtill blows, i have found this to happen when the starter is shorting out inside, if you turn the key and the fuse doesnt blow then replace the starter, remember the small wire on the starter. good day.

probably a bad starter solenoid, first remove the negative battery cable, then remove the two wires from your starter, wrap them in black tape so they wont short out on anything, repl,ace your fuse and hook battery back up and turn key to start, no blown fuse-bad starter, if it blows the fuse it's a wiring short and you should take it to a qualified mechanic

Unfortunately, many possibilities. If you have time, start by removing both reverse lamp sockets from light assembly(and keep from touching any metal), remove bulbs from sockets, CAREFULLY INSPECT sockets and wires. New fuse of correct rating. Turn key on and try again in reverse.
Fuse still blows: Next place to look is transmission reverse electrical switch and wiring as far as you can trace looking for burned/stripped wires near transmission and wires by sockets
Fuse doesn't blow: Turn key off and install one lamp in socket at a time. DO NOT install sockets into fixture at this time. Test. Remove first lamp to check second. If still O.K., each socket back into fixture(one at a time same as before)and test. Most common problems: Sockets contaminated, wires shorting at sockets, bulbs installed incorrectly shorting to ground.