I had this problem, it is the crank sensor on the bell housing of the transmission. This tells the computer where the TDC is or Top Dead Center. There is also one for the cam shaft. I would see about changing this out or looking into this. They do go, and it sounds like a lot of other things, but if it fires and dies, you can push in the shraeder (sic) valve on the fuel injector area to see if it has fuel.
[h=3]Operation[/h]In a typical Jeep application, the ignition control module (ICM) is located in engine compartment. It consists of a solid-state ignition circuit, as well as an integrated
ignition coil that can be removed and serviced separately. Electronic signals from the ECU to the ICM determine the amount of ignition timing or retard needed to meet engine power requirements. The ECU provides an input signal to the ICM. The ICM has outputs for a tach signal to the
tachometer and a high voltage signal from the coil to the
distributor. The crankshaft position sensor senses TDC (Top Dead Center) and BDC crankshaft positions, as well as engine rpm. This sensor is secured by special shouldered bolts to flywheel/drive plate housing and is not adjustable.
This is for your 1988 year. Good Luck! I am on my 5th Jeep Grand Cherokee over 27 years! Love me some jeeps..hate the sheet that happens, but then they usually can be fixed easily enough!