for starters i have a 1990 cherokee with old renix 4.0 straight 6

ok well i turn the key and it sits and cranks but no pop its not getting spark to the distibutor but had ignition mod and coil tested they are fine guy at napa said it might be the computer? but i dont know what to think cause its $150 and im broke.

second i have a wire on my fuse box that is bothering me and i dont know what it does (kinda dumb questions but first jeep still clueless...and not my picture) but the wire goes from here to here on picture.

 

Have you checked your CPS?

 

I been told that with bad cps it wouldn't even crank right or at all

 

Slim chance but an easy check: Pull the distributor cap and make ture the rotor spins when you turn the engine over. If it doesn't the timing chain is broken.

 

Try this first:

Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the 3.5 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.