Why won't my 5.2 GC start even after replacing the Crankshaft Position Sensor?

I’m looking for ideas before I buy a new computer for my car. My Jeep keeps turning off while I’m driving. I took it to the mechanic, and they said the problem was with the ignition coil and wire. They fixed it, but three days later, it wouldn’t start reliably. Sometimes, even after a short break, it wouldn’t start again. When I turn the key, the engine tries to start but can’t. If I keep trying, it eventually starts weakly. Yesterday, it wouldn’t start at all when I finished work. Today, I changed the Crankshaft Position Sensor after doing some research. It was a tough job. Even after replacing it, the car still won’t start. I checked for error codes, but there aren’t any, just the ones that show up when I disconnect the battery. I’m thinking of replacing the computer next unless someone has a better suggestion.

Here’s what I’ve done so far:

  • Replaced the fuel filter
  • Checked that the fuel pump is working well
  • Replaced the crankshaft position sensor
  • Looked for the “magic screw thing” on the computer (didn’t find it)
  • Replaced the ignition coil and wire

I’m still having trouble, even though I can see sparks from the plugs. What could be wrong with my 1994 Jeep Grand Cherokee ZJ 5.2L?

I think it could either be a problem with the spark plugs or the alternator.
Some of the common problems associated with bad spark plugs include ignition and start-up trouble, rough idling, sluggish acceleration, declining fuel economy, engine misfiring, and engine knocking.

As a one-time Jeep owner, I would recommend:

Check the Rotor and Distributor Cap: Check for burns or damage. When you turn on the ignition, make sure the rotor rotates. If so, remove it and carefully inspect it.

Check Fuel Pressure: Double-check that the fuel pressure is within the recommended range. Inspect the gasoline filter and test the fuel pressure regulator.

Inspect the ignition coil connections. Make sure the connections are secure and that power is reaching the spark plugs. Faulty connections can result in weak sparks or sporadic starting problems.

Revisit the crankshaft position sensor (CPS): Ensure that the new CPS is operational and properly connected. New parts can occasionally be faulty.

Consider the computer (PCM): Check the Powertrain Control Module, which regulates ignition timing and fuel injection. Explore repair or replacement options if necessary.

I went through a similar ordeal with my own car a while back. After trying various fixes and replacements like you have, I eventually discovered that the issue was with the Engine Control Module, also known as the computer. It’s possible that your ECM is malfunctioning, causing erratic starting behavior despite your efforts to address other potential causes.

Replacing the computer might indeed be the next logical step, but before doing so, I’d recommend double-checking all the connections and grounds related to the ECM, as loose or corroded connections could also lead to similar symptoms. Additionally, if you haven’t already, it might be worth having a professional diagnostic check done to confirm whether the ECM is indeed the culprit. I hope this helps, and I wish you the best of luck in resolving the issue with your Jeep.