Question:
When I am driving the engine shuts off sometimes. Sometimes it will start right up other times it takes awhile. I need to know if it could be the fuel pump or aould it be the fuel filter. The altenator is fine I got it tested
Answers:
If the engine is shutting off instantly, then it sounds like you may have an electrical component that is shutting off. This could be a relay that controls the fuel pump, the fuel pump, or an ignition related component. It's unlikely related to the fuel filter, or the charging system. Have a shop check the trouble codes for you and see if any codes are stored, this is a good place to start.
　
I was having the same problem with my 1999 Grand Jeep Cherokee (4.0)right before Christmas. The crankshaft position sensor was replaced and so far so good. The sensor cost about $40. Initially they couldn't find it but now we know it is on the top left side where the engine connects to the transmission. It is held in place by one bolt.
Before you but the part check the code on the truck yourself to see what code pops up. Check it by turning the key until the odometer shows the mileage and turn it off. repeat until the mileage is replaced by a code. Write the number down and google the code. Mine was P0320
I had this same problem with my 97 grand cherokee. I have a website with some valuable info for you, it could be your pcm. It seems to be a pattern when these jeeps get around 150,000 or so miles. A quick and easy way to figure out if it is or not is to start your jeep and let it idle. Open the hood and then push on the top left corner of the pcm. If your not sure where it is or what it looks like, it is a silver box with 3 big wiring harnesses plugged into it. It is bolted onto the firewall on the passenger side behind the coolant overflow tank. When you push on the pcm on the top left corner (the corner closest to the engine) the engine will stall, cut out, studder, and die. If thats the case you can take out the two screws that are below the connectors that plug into the pcm and replace them with shorter ones. Also, you should take a small piece of wood or a piece of PVC pipe and wedge it in between the firewall and the pcm on the same side that you pushed on. Hope this helps.