99 Jeep Cherokee 4.0
125k miles
aw4 /242

Backstory:

Turned on the xj to go to work. Let it warm up as always do and took off. About 5 minutes later my radio turns off. I thought the face was loose so i take it off and reattach it. It did this 2 more times and then i saw that my voltage was pegged at 19v and my check gauges light was on. I made it to work.

8 to 9 hours later after work i turned it on. started right up. Ran what seemed like a little bit rough and drove it 100 feet to the office gym. turned it off and went inside.

1.5 hours later i came out. let the fuel pump cycle as i always do, attempted to start but it wouldn't start.
Tried a few times but it wouldn't turn over. If it turned over it was like for half a second and it would die. If i gave it gas i could get it to stay on for a few seconds and as soon as i let the rpm come down it died. all electronics work and it has battery.
MY dad said it sounds like my Crank position sensor but has anybody gone through this? any ideas and or input? the battery terminals look fine and ground to the fender is attached.

 

It could be. When my crankshaft position sensor went out on both my Cherokee and Wrangler I had issues with my gauges and my jeep would intermittently start and misfire at higher rpms then it wouldn't start at all until I finally replaced it.

If you can check your battery with a volt meter and see what it is putting out just to make sure it isn't the issue it should be 12.6V when starting and up around 14V when running. If it was actually 19V it probably would've done some damage to your electrical system or blown some fuses.

 

There is no reason to suspect the crank sensor.

Sounds like you have a toast alternator or really bad connections to the battery. When sufficiently corroded, a voltage rise can be artificially created and make it look like the system is running too high. I've drained my battery quite low before, and the Jeep required like 5-10 minutes of running at higher RPM (foot on the gas) before it would idle properly. The alternator placed such a drag on the engine that it literally stalled it.

Start at your battery posts and follow the wires! You need to take them apart and clean them.

 

This has the hallmarks of poor/corroded electrical connections under the hood. Before ripping into anything or changing any parts, they should all be cleaned and tightly reconnected.