Sounds like you have multiple problems. The only way to get them fixed is to do one thing at a time. It's like peeling an onion. You peel away one layer, and that exposes a layer beneath. You fix one problem, and that exposes another problem.

Your 12.8 volts at the fuses is wrong. You should see full battery voltage, which is around 13.8 on a fully charged battery. Check that at your battery. Any troubleshooting you do will be an exercise in frustration if you do not start with a good, fully charged battery. Get that right before you do anything else.

Once that's done, time for some cleanup. You probably have a lot of bad connections and corroded wiring. You need to track them down and fix them one at a time. There is no silver bullet, there is no magic one thing that will fix all of this.

First, check the wire that goes from the B+ to the PDC (Power Distribution Center. I think that's what you are calling the "brain box".) Remove it completely, and inspect it closely. If you see corrosion at either end, replace the whole thing. Don't clean it up, don't try to polish the turd. Replace it. Use dielectric grease on the connections to prevent corrosion.

Next, the ground wire from the B- to the fender wall. That is notorious for being bad. Again, if you see corrosion at either end, replace the whole thing. Don't clean it up, don't try to polish the turd. Replace it. When I did mine I replaced the wimpy sheet metal screw that holds the connector to the fender wall. They get really rusty. I removed it, drilled out the hole, and cleaned the paint from around the hole back about a half inch with a wire wheel. Then I reached in from behind with a 1/4-20 hex head bolt, about 1" long. (OR maybe it was 3/4" long.) The wire was replaced with an upgraded size, with a 5/16" eye on the end for the fender wall. The bolt comes through from behind, a flat washer next, then the ring connector, another flat washer, a lock washer, and a nut. Everything liberally coated with dielectric grease to prevent corrosion.

Next, pull all of your fuses one by one (so you don't get them mixed up) and spray the contacts (fuse AND fuse box) liberally with CRC contact cleaner. Spray both with the cleaner, then push the fuse in and pull it out a few times. This will clean up the contacts.

By the way, that ground strap on the firewall is probably the least important ground you have. I wouldn't spend any more time on it. If it is carrying any appreciable amount of current, something is very wrong somewhere else.

I would not be surprised if doing all of the above solves your problems. If not, at least we''ll have peeled some layers and we can go from there.

You might also want to check Cruiser54's tips for refreshing your grounds. They are specifically for the Renix models (older) but the principles apply to all.

Bad grounds and corroded connections and wires can do some very strange stuff that will make you pull out your hair.

 

Ok. Well I cleaned my grounds. I got my batt fully charged and got some new batt connectors. As im installed new connectors I notice my groud wire from batt to fender body beside bat is a little corroded. I replaced the that ground with a fresh ground wire. My negative and positive cables from battery are a little corroded inside the insultion. Both of them the whole length of wire.. I dismantled fuse ox uder hood to inspect. The metel plate in there was a little corroded so I clened it..

do you think there is more then one problem? Do you think mybe the Crank sensor is responsible for or could be for all isuues.

I notice I have power coming into my ASD. But how do I go abouts testing if the asd is sending power out.

with my key in on position my volt meter, gas gauge oil pressure dont move. My tripo lights up I hear dinging from key on all lights on dash work.

My brain box or ecu the computer has 3plug connectors on it. One black one grey one white.
the black connector closest to headlights while key is on I only get power to one prong there. Is this normal. I read about the torx screws in pcm do you think I could have luck turning the screw out a little? Or even digging into pcm maybe see if it has bad connections.?

as for little green corrosion inside my battery wires do you think this is the problem? If im only getting 12v from battery wire maybe tht corrosion is just enough to halt the volt flow.

as soon as I get a few bucks im pulling a Crank sensor from the auto wreckers and trying it.

does my key need to be on while testing volts in wires.

also I hve to use a screwdriver to start the jeep witch worked fine for months. Do you think tht has something to do with it?

Thank you very much fr your help so far. I didnt know these damn things were that picky with voltage and stuff. As for testing frther then fuse box im lost...

 

Do as Mark suggested "DON'T" clean the cables replace them if they are like you say. That would be step #! on the list on where to start if they are that bad.


You need to listen for help to work.

 

Here you go. Quality cables
https://www.cherokeeforum.com/f73/up...cables-221513/

and don't go to the junkyard for a cps sensor. New ones aren't that expensive.

 

Im going out to add clean grounds again maybe better. Yes my battery cables have corrosion inside them. Im going to replace my battery cables and test for volts. Guess ill start with B+ cable then -.. thanks guys ill repost my readings at battery and fuses ounce im done. Thanks again.. god damn k hope this helps...

also could tranny fluid on connectors underneath cause a short or short circut somethjng.

my rear o2 sensor, the 3 harness connectors by trans dipstick were all covered in tranny fluid from the leak... damn wish it would just start..
my first attempt at starting engine after tranny swap it fired right up shut off tried to start again and no spark.. uhg...

 

I think I'm done here.

 

Right? lol I saw this look on your face.

 

Well you gave a valiant effort! Lol!

 

Haha, No really I get it guys. And I really appreciate all of your input. Youve helped me more then you know, im just a curios guy.

So as im under the jeep I happen to look up and see 2 grounds below my computer holding 4 wires.
damn thngs were rusted fast so bad, and if she is as picky as you say.. im so excited like god damn kid on Christmas Day to see them damn rusted grounds!!!!!

so im cleaning them good replacing corroded wires and adding extra grounds.

My question is my damn washer fluid never worked when we got it. As im looking at them lovly rusted grounds I notice the resoviour for washer fluid..
ill be damned if that connecter and wireing there isnt deteriorated rusted up horrible..
also a few connectors in front maybe fog lights? 3 are snipped off. I have 3 plug connectors but no where for them to go?


you guys are awesome. Ill be damned if I have this fired up tonight..

 

No spark, no fuel pump prime, no trouble code!
The exact same symptoms i had when my Jeep was stored for a few months.
In fact it ran fine before storing.

Yep the old crank sensor and possibly other gremlins as others mentioned.
If the corroded wires don't fix the problem, try changing the crank sensor and with a Mopar one at that. If nothing else you'll have a new sensor.

 

Well that was an interestng night.. so if this jeep isnt pleased having a god damn orgasm over her new grounds then shes a lying... got volts up to 13.2 _13.4
unplugged the CPS tried key on. Volt meter still reads 0. Gas gauge rads empty, dash lights work fine now however I am not getting the glitchy haywire jumping tacks..
Plugged cps back In still no fire no spark no fuel prime.
so I guess its boiling down to the damn Crank sensor.. suppossing I have no money for a week or more for the sensor im dead in the water till then.. If you guys have any other input or mods or tweaks I can do to this thing untill then I apprecite it..

Just hoping for damn sure its the cps after I get one and this baby fires up like no tomorrow..

if not I guess ill be peeling onions? For awhile more

 

Make sure and get oem quality sensor

 

Hey I just want to say thanks again Mark and everyone else. Im just sitting here re reading this post and just browsing threads.

I feel good about today though anyway. I want to
post some pics tomorrow if Im allowed anyway. Definitely didnt know a little corrosion goes a long way I guess.
Replaced 4 battery wires, the battery ground wire to body replaced.. I just polished the little self tapping turd actually cranked on it without it stripping lol.
2 grounds below ecu? All shiny greased up, I didnt replace them wires idk where they go.
4 wires on 2 grounds distributer side of block shiny. And another hard to get one on block by dipstick, holding 2 wires one eyelit shiny.
I got underneath and blew out connectors, plugs, wires. Reattached starter wires they were nice looking. Alt wires I pulled and cleaned contacts.



also is there anything I should adjust or do since I put in the transmission..

And actually the swap wasnt to bad for one guy.

What Jeep You guys Own?
Mine is 98 cherokee classic. No mods. F in love it cant wait to drive it again

 

Make sure to adjust the TV (Throttle Valve) cable.. If not adjusted correct it will take forever to shift into gears,,high rpm shifts..

 

I have experienced a failed CPS and the failure of an aftermarket CPS a month later. Here is a possible reason...