It looks like there was a transition during 2000/2001 and some rangers had a power distribution box with the 50 amp ignition fuse in position 11 and the other box has it in position 5.

The information on the wiring diagram says it's fuse 11 (50 amp) BUT looking at some 2000 Ranger fuse box diagrams, they show the ignition switch being powered by fuse 5 (50 amp) and fuse 11 being a 15 amp fuse. (engine compartment fuse box). 

Fuse 5 (50 amp) seems more likely so let's clear this up.

Is your fuse #11 a 50 amp fuse like on the wiring diagram? If your fuse box is laid out like this then the ignition switch is getting power from fuse 5:

https://i.postimg.cc/8kJyjSb6/imageedit-1-3430440805.png

So to keep this moving along I'm going to assume your fuse box is like the one above and the ignition switch is getting its power from Fuse 5.

For right now that's irrelevant for this next test.

You discovered this voltage drop with the starter relay out (key at Start position) at relay terminal 85  and you've traced the voltage drop all the way back to the the red and blue wire connector at the ignition switch.

So pull the Starter Relay out again to stay consistent.

We need to determine where that voltage drop begins on the "Input voltage" side of the ignition switch connector.

Here's the pinout of the ignition switch connector:

https://f01.justanswer.com/online007/3cb7ad4b-bf63-43c6-95a6-03ae41d75f41_switch.gif

See the terminal labeled "STA"? That's the Red and Light Blue wire you've tested before. It gets voltage when the key is in START and then sends power through the 7.5 amp fuse (24), through the neutral switch, and to the control side of your starter relay. (where you're measuring 3.35 volts at every part of that side of the circuit).

OK, now notice all of those yellow "Battery Input "wires to the ignition switch?  There's like 5 of them.

But if you look at a close up of the ignition switch on the starter circuit wiring diagram which I posted earlier it looks like there's 1 yellow wire going into the ignition switch and one Red and Light Blue wire coming out. (you replaced that switch so you know that ain't right)

https://i.postimg.cc/Hn4jptTz/Screenshot-2021-08-27-1-57-42-AM.png

If you notice there's a dotted line around the ignition switch in the diagram. It's telling you that it's only showing only the  part of the circuit that you requested. (starter circuit).

And what is relevant is that it shows the "power in" to the ignition switch for the part of the circuit you're working on comes from the Yellow wire on the Ignition Switch connector terminal labeled "B4"

and the "power out" of the ignition switch that you're working on comes from the Red and Light Blue wire on the ignition switch connector terminal labeled "STA".

So you want to check the voltage, with Starter Relay Removed, Key in START position, by backpinning the B4 connection on the ignition switch connector.

Is there only 3.35 volts there too?

But don't stop there. You can see all of the Battery Voltage inputs to that ignition switch connector from the pinout I posted.

B1, B2, B3, B4, and B5 (Yellow wires), Check that they all have battery voltage especially in the Key Start position.

Here's why

 There's only 1 wire coming from the 50 amp fuse to the ignition switch.

Just before it gets to the ignition switch it's spliced (crimped) into 4 seperate wires. The 5th Yellow Battery Voltage wire to the ignition switch is "jumped" from 1 ignition switch terminal to another terminal.

So you want to test the voltages by backpinning each of the yellow wires on the ignition switch

.

If any has low voltage you want to move UP in the wiring circuit  (peeling open the harness wrapping) to a point before the splice/crimp and using a pin to pierce the wire, check the voltage on the single wire that's feeding the 4 wires to the ignition switch connector.

https://i.postimg.cc/C10Nz4Wt/ranger1ign-zps3de0ddb9-jpg.jpg

Let us know what you find out
.