So a few weeks ago my 97 cherokee xj sport would crank but not start. It took me a while to figure out it was the ASD(automatic shutdown relay) with the help of a code reader. But also the Battery Temperature sensor wire is cut from corossion. So i replaced the relay and it fixed my problem, so atleast I thought. I came out from class to start it and again same issue with the cranking and not starting. So a weird temporary remedy for this issue which worked for me was to disconnect the coil wire from the ignition coil, crank it for 3 seconds, connect the coil wire back and it started rough. I let it run for 5 mins, started again no problem. Even after I was at my friends and let the jeep get cold it started again no problem. The only codes im getting are for the BTS and 02 sensor which i took out a while ago when i removed the cat.

Anybody think its my CPS or maybe a shot ECU? Could the BTS prevent it from starting?

 

This was yesterday, I just went to start it now and it started no problem first try. And its been sitting all night in the cold...Maybe bad coil wire?

 

If anything, I would not condemn your ECU. This BTS is provides info to/for the ECU, IIRC to regulate alternator output/charging of battery. A faulty sensor will give faulty or no info at all. And a weak battery can cause a no start situation.


Did you measure voltage of battery?
When was your last complete tune-up done?
You could measure the coil wire for resistance, if you suspect its bad.
And checking for spark will give you an idea about the quality of the spark your getting (orange/white is weak, blue snappy spark is good)

 

Next time it doesn't want to start you need to check if you have spark and fuel. There has to be something missing for it not to start.

 

So its possible that the BTS could cause sporadic issues relating the battery and starting? I dont think the battery's weak because when I start it it fires up no problem, no hesitation at all. The issue I'm having is most likely related to constant spark to the ign coil. Im gonna measure the voltage to the coil wire and the battery tomorrow when I get a chance. Is it possible that the CPS is starting to go? I wouldn't be able to start it at all right?

 

Very possible. If the CPS is going you will lose spark and fuel.

 

So if the cps is going it can still operate? Meaning every now and then the car wont start because of the CPS? I thought the CPS either worked or it didn't, black or white kind of thing, no?

 

It can act that way. My cps would act up maybe once ever couple of months and it ran like that for almost 3 years until it left me stranded and completely went out. Do youself a big favor and get an OEM cps. after market ones are known to be bad right out of the box and if they do work thay will have a limited life span.

 

CPS typically works intermittent before it goes out completely. Agree completely with the advice regarding OEM.

 

Thanks for the advice guys! So reconnecting the coil wire just fixes the CPS temporarily?

 

It happened again, so I reconnected the coil wire and it started again rough the first time but ran completely fine on a 30 minute trip home. This makes me believe that its not the CPS but possibly a faulty Ign coil.. considering the new one i put in I bought from Adanced Auto.. I'm gonna put the oem coil back in and see if it solves anything. It seems to only do this on longer drives, like 30 minutes..