As of recently my 90 cherokee straight 6 has been having some serious issues.. there are a couple issues going on so ill start with the longest issue..

1) When i go to start it up i will get zero power and it wont turn over or anything. I still get power to everything else though like dome lights door locks windows radio ect.. Normally if i let it sit for 5-10 min it will fire right up like nothing was going on.

2) Basicly same as #1 but this time it will just turn over and over and over till the battery dies if i go that long. But if i let sit for 5-10 min it will fire right up..

3) when i fire it up my brakes are hard and my booster pump kicks on every 20 seconds or so then shuts off and keeps doing this till i turn off my jeep. After about 1 min or so the brakes go back to normal and all is well but the booster pump keeps kicking on still.

4) when i go to fire it up in the morning some times the battery will be dead.. Not sure if this has to do with what ever else is going on.

I have changed all spark plugs, cap n rotor and had my battery checked with no prevail. i have tried 2-3 other things but nothing seems to fix it.

 

Welcome! Here's a few things to check.

*If you hold the key over, and jiggle the shifter in park or neutral and it starts, it's your NSS. http://bc4x4.com/tech/2010/jeep-neut...ty-switch-nss/

*Battery gasses have a nasty habit of helping a thin, hard crust form on the bat post's and clamps. They can look pretty good, but that micro-thin layer is a surprisingly good insulator. SHINNY! Lead is what you want. I use a pocket knife, (gently), for the insides of the clamps. For the posts I might use one of those post cleaner wire brushes, but still scrape it with a blade. If you have a condition where you have power, (dash lights ect.), then when you hit it power goes out altogether, that's a common result of a layer of oxidization there. Btw, a half *** connection could be expected to get hot during cranking, or while it's trying. Cleaning those is something to do now and then anyway, so if you are having starting problems, you might want to make sure you have bare lead on lead. Might save you some grief!

* *Anyone with an 87 to 90 Renix Jeep has two or three minutes to see that their CPS is putting out at least .35 AC volts. I don't mean to come off rude, but if you can't connect a meter and turn the key, we may not be much help. Easy as one, two three!
AC voltage CPS test; Small clips on the meter leads really helps. You need contact with those little pins while it cranks, maybe get someone to help.
#1 Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps. (it's a three wire plug, with only two wires)
#2 Probe the two wires to the cps with the digital meter set on AC volts, a 200 scale on mine. Yours meter may have a lower 2 Volt, or “auto range”.
#3 Crank the engine and note the voltage. (jump it if your battery is low). .35 ( is minimum. .4 to .8 is more like it.
*There's is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage there can cause all sorts of trouble.

Granted, making sure the battery posts and clamps and terminals are bare, shiny lead can take a few minutes, but that and the other there I mentioned might be done in 15 minutes. All highly recommended before you move on.

This is a link specifically written for your Jeep. Do Cruisers tips, 1,3,4,and,5, you will be glad you did! > https://www.cherokeeforum.com/f51/cru...x-tips-153657/

Last, as far as the dead battery in the AM, for starters, make sure no dome lights are on, and see that the under-hood engine compartment light is not the culprit! (remove the bulb?)

 

thank you very much dflinstone i will do everyone on here and update as how it goes. I also heard that it could be my ignition switch?? would that cause my problems as well?

 

update.. So i took apart my battery cables cut stripped the rubber and put them all back together so there is a strong connection and then i took off my nss and cleaned it all up re greased it and put it all back together.. Jumped my jeep and it fired up drove it running around town for 3-4 hours ( turning off and re starting alot ) and it started up no problems. Went to start it this morning after sitting over night and nothing again.. i wiggled everything tried everything even bypassed my NSS and it still wouldn't start..

 

Tried jumping it and nothing.. now it wont even jump.. got under there took nss apart again everything was still connected put together moved million times in the pouring rain and still wouldn't jump no matter what i did.. im getting so frustrated its not even funny..

 

OK fist, I said, "If you hold the key over, and jiggle the shifter in park or neutral and it starts, it's your NSS"

Now you have been into your NSS twice. Did doing that jiggle thing do anything?

I'm not quite sure what you mean by, " i took apart my battery cables cut stripped the rubber and put them all back together"

So you "bypassed my NSS and it still wouldn't start."

Please do not get me wrong, what I want is to be really clear.

If the battery Voltage is about 12.5 and you "juice" the green solonoid wire, and nothing happens, likely the starter is done. The solonoid can be juiced right at the relay (see diagram) or right on the starter. Caution! It will start in gear doing this, be careful!

A sure sign of a bad starter is if it works after a good smack with a hammer, or if it works with a good smack with a hammer while someone is holding the key over on start.

The Green wire that activates the starter goes here, "middelish" on the starter relay. See if it works juicing there, or on the starter. If it does, the Ign switch or the relay might be the problem.

 

What booster pump?

 

So i did do that Dflinstone and nothing happened. thought maybe one of the pieces came out in my nss when i put it back together only reason i checked it again. As for it not starting i took my terminal cables and cut them back so it would be fresh cable for good connection. I also cleaned my ground the negative terminal cable connects to on back of motor and also the ground on back of firewall. after doing so she fired up..

The booster pump i was talking about is the ABS pump/motor. the 90 jeeps have the ****ties brake system they combined the abs and power brakes into one and only sold this package for 1 year because it was such a hunk of ****.

 

So you are good now?