Hi All, first post here.
I've acquired a little 1990 single cab 2.3 5 speed Ranger that was bought new by the father of the guy I got it from. It only has 109k miles, but it hasn't ran in a few years. There's a lot new from tires, shocks, to alternator and even the ECU. I actually got the truck through my father in law who's neighbors with the PO so I've never talked with him and only getting second hand info about it.

I've googlied the webs trying to understand this system as well as studying the wiring diagram, but I'm not very electrical savvy.

Questions:
It's not getting spark to the plugs, so I started at the wire that feeds the ignition control module to start testing there. Supposedly that Red/Green Stripe wire is supposed to be hot with key on, correct? No power out of that wire, so I back track to ignition switch and see power at the two yellow wires but again, I'm a dummy, so decided to skip that part.

I hooked power directly to the red/green wire #1 going into the ICU but still no spark to the coil.

If the ICU and Crank Position Sensor are working correctly, can that red/green wire #1 going into the ICU be hot wired to power the coil pack? It makes sense to me that if everything is working, power to that wire should allow it to start..

Follow up Questions..
I pulled the wire housing off the firewall where it connects to the fuse box and thought that I located the red/green wire pin, but that pin activates the fuel pump when I put power to it. Is that what power to the red/green wire is supposed to do? If so, the power isn't transferring to the ICU because that wire still reads no power. I started to unravel the wires to see if there's a break somewhere but that's gonna be a big mess and I really don't want to do it.

So.. I'm about ready to just buy a new ICU and Crank Position Sensor and start over.. I already have the cover off and want to replace the belt anyway, but I hate diagnosing by replacing parts.

Any help would be greatly appreciated!!

 

Welcome to the forum

Lets start at the source, the battery for now
Battery negative is the ground for all devices, there is no 12volts if there is no 0volts(ground), that's important to remember
If you disconnect battery negative nothing electrical will work, same as disconnecting battery positive

So to test for voltage you need a good ground for the meter or test light same as you need a good connection to the 12volt wire
OK, thats out of the way

12volts from battery positive travels to the engine fuse box, there is a 60amp fuse in that fuse box that has the two Yellow wires you mentioned earlier, they go to ignition switch under steering column, you tested the wires and they have 12volts so that fuse is good
On the ignition switch there should be a red/light green stripe wire, this wire should have 12v when key(ignition switch) is ON, if not then ignition switch is bad

This red/green wire powers the whole spark system, the ICU, BOTH Coil packs, and crank sensor, it ALSO powers the EEC Relay, turns this relay on to power up the computer(EEC) which in turn would power up the fuel pump, computer turns on fuel pump for 2 seconds when it boots up

Which is why you heard the fuel pump when you jumped 12v to the red/green wire, you turned on the computer

Start at ignition switch to see if its working connecting red/green wire to yellow wire to get 12volt

Diagram below for 1990 2.3l spark system

The 2.3l ICUs were know issues on 1989-1994 Rangers
Test for 12v at the coils with key on as well as ICU

One heads up, only the exhaust side coil pack works with starter motor on, the intake side will only spark above 400rpm, so ONLY TEST for spark on the exhaust side coil pack and wires

When you turn on the key the CEL(check engine light) should come on, this means computer is booting up(EEC Relay closed)
When you activate the starter motor the CEL should go OFF, this means the ICU and crank sensor are working and sending a timing pulse to EEC(computer)

 

Wow, thank you Ron!! You covered some missing info that will help immensely. Thanks again for the detailed writeup! I'm gonna finally spend some time on it this morning.

 

I didn't look at it yesterday but I did spend a little time with it today. I cleaned up the ground wire to the battery and will definitely be replacing the cables. I know I said I was an electrical dummy, that is my weak area, but I've restored several cars and trucks including my 72 c10 that I swapped over to a short frame and did a complete restoration myself including all the rust repair, bodywork and paint, but for some reason just have a hard time with electrical. I guess I know a good amount, but there are a lot of questions that I come up with and I really appreciate the help from you fine folks.

So, I am still not getting power to the red/green wire at the ignition module. It's got good ground. The wire coming from the fuse box is hot and powers the fuel pump, but nothing at the ICM. I have that wire cut and stripped and when I tie it back together and hook it directly to the battery I get power to the intake coil. That coil pack is new as well as the wierd and plugs, but no power coming out of it when the engine cranks. I plan to take the other coil for exhaust spark and trying it on the start side, but before I do I want to know if I'm missing anything.

I'm draining the bad gas now so if/when I do get it to spark it'll have a fighting chance.

 

Well red/green wire is powered by ignition switch in the cab, and with key on EEC relay will close and then fuel pump relay, so if you hear fuel pump then 12v is making it out of cab and into the engine bay from the ignition switch

This wire is spliced in engine bay and its a big one, S122, 6 red/green wires spliced together, so if both coils have 12v with key on then at least part of that splice is OK but the wiring going to ICM is not
I don't know where to look for that splice, but if you can follow any of the red/green wires it will lead you to that splice