So this is a weird one,

I've had running/starting issues and have done a whole bunch of diagnosis and whatnot to get the jeep back to running good, here's where I'm at now:

I just installed a brand new OEM CPS, reset the ECU as you should with a new CPS, and she started and runs great. But, once I shut it off and tried to start it again, no crank, no nothing, clicks once and that's it.

Here's the weird part though, after the no crank/no nothing, I disconnect the positive battery cable and reset the ECU, and she started and runs and drives fine, but as soon as I shut it off it won't start again.

Can someone please point me in the right direction to what on earth is going on?
Thanks in advance

 

Sounds like it could be a bad ECU.

 

It could be an Earth or a positive connection, clean everything up and it'll probably start every time. I hate to say you probably wasted time & money just replacing the CPS.
What all did this "diagnosis" consist of exactly?

 

The old CPS was bad, that's forsure, it was the initial problem. The backstory is it died driving home one day, no start/no spark, replaced the cps with a non oem one and it started fine but ran really rough, replaced that cps with an oem one and now runs great, but will only start if I reset the pcm, not the ecu, just to clarify.

In terms of diagnosis, every fuse/relay was checked, wires and grounds were checked/ cleaned, battery was load tested and is fine, fuel pump checked out good. The only thing that hasn't been tested is the starter.

In terms of this issue, to clarify, it will only start if I reset the pcm, and it fires up first try and runs good. if I don't reset the pcm, it clicks once and doesn't turn over. Could it be a the starter solenoid or a starter relay issue?

 

It only starts when you disconnect & re-connect the battery, that's where the connection issue is.

 

Jordan made a very good point in a previous post about the battery cable "jumping" when the starter tries to draw the massive amount of power it needs to fire the starter. Everything else ran fine, no radio resetting, lights worked, etc.
Therefore, considering what Turbo is saying, you need to make sure that the battery cables are both clean and -tight-.

I'd put some terminal or di-electric grease on the terminals and make sure the cables are tight AF - let us know if that helps.

 

That's the plan for today, I'm going to clean up the battery and recheck and tighten all the battery cables, might just replace them for peace of mind and see if it solves the problem

I realized my explanation of the issue was somewhat unclear, when I go to start the jeep I get a relay click, that's it.

EDIT: to even further confuse this, I just hosed down the engine bay, including the starter, because it was nasty and I was planning to remove the starter, and now it starts? I'm guessing the starter is going/ gone bad and somehow cleaning it is now allowing it to start. Can dirt/oil on the starter cause a no start?