Cranks but no start

Will need more info to proceed any further. What type of engine? V6, Inline6, V8?
Do you have pressure in the fuel rail? There is a fitting that looks like a bicycle/car tire air fill valve on the fuel rail. Unscrew the cap, then press the small "button" you'll see in the middle of it - Does fuel spurt out, or just dribble out? (Do this after trying to crank the jeep to give the fuel pump a chance to pressure it up if it IS working.). Do you get a spark at any of the spark plugs? Need to know these things. When you try to start it, what indicator lights do you see in the dash (Example: check engine, brake, seatbelt, ABS, etc.). Do you know if your grand cherokee has the ability to do a self-diagnostic and spit the codes out at you using the check engine light? I have a 1996 Jeep Cherokee that will do this when I do an on/off sequence using the key, but only if your check engine light is working.
To do this, turn the ignition key ON, OFF, ON, OFF, then finally ON. (On is the position just before that extra click that starts the jeep) The check engine light will blink the number of the first code digit(count the number of flashes), then pause about 2 seconds and blink the number of the second code digit. If you have more than one error code, the light will pause about 3 or 4 seconds, then blink the first and second digits of that code the same way as before. When the computer is finished blinking "codes". It will flash 5 times, pause, then flash 5 more times to tell you that is the end of the sequence. Post back with what you find out, and someone should be able to ansewr with more info if you need it. GOOD LUCK!