JEEP Cherokee Classisc begins but does not turn on

Before buying, I had to test everything. You already said you changed the ECU, crankshaft sensor, and spark plug, but you haven't tested the distributor and coil. Remember that the distributor has a pickup coil. The same thing happened to me with one of my own, and it was the pickup coil. In the end, the pickup coil had a short circuit that fried my ECU, and to save money, I installed a carburetor. But your problem isn't that; it's about testing the sensors and then buying.

I have some really good information about this. I also changed an ECU and couldn't get my Cherokee Limited to start, but that was an 8-cylinder. What model is yours?

But first, check fuse number 12, a 10-amp fuse, inside the dashboard compartment, not in the engine compartment. Note that fuse number 12 isn't marked on the cover (meaning it doesn't have a label indicating its function). This is a power fuse (I don't remember if it goes to a relay or directly to the ECU). To access it, you'll have to remove a couple of 10-amp fuses that are held in place by a kind of yellow clip. Does that make sense?

That fuse blows, and no matter how much you crank the engine, the truck will never start, and no matter how many ECUs you install, it will never start. I have a diagram I can share with you, but first, check that fuse and let me know.

Hey buddy, this is pretty simple. First, check if the CHECK ENGINE light comes on in your vehicle's instrument panel. If it doesn't, replace the ECM fuse. Once you've confirmed that the light comes on when you turn the ignition on, follow these steps to scan the computer, and it will tell you where the problem is. Just to clarify, you need to crank the engine for a couple of minutes WITHOUT DISCONNECTING THE BATTERY so the computer can store the DTCs (Diagnostic Trouble Codes). I've attached instructions on how to do it; it's pretty easy. Good luck!