98 jeep 4.0 crank no start

it could be a crank sensor, ignition module, coil, if this has a distributor could be pickup coil or a bad distributor, bad cap/rotor. could also be a PCM problem on the ignition circuit.

keep it simple first disconnect coil wire from distributor leaving coil connected, put a screwdriver in wire place it away from fan or other moving parts such as belt , and crank engine, u shld see spark. if not u found ur problem. coil needs to be replaced

See if your getting spark at the ign. coil first (passengers side on that year) if you are change the crank shaft sensor making sure you mount it as close to the engine as possible so it never gives you trouble again.

Crank but won't start

If the check engine light does NOT come on when cranking at the times when it won't start, then your ECU is in need of repair. The engine will only start after the check engine light comes on and the ecu is what controls that. It's likely going bad, causing the delayed start problem typical of early 90's jeeps. Repair or replacement services for your jeep ECU are available on ebay.

Check for a signal at the ignition coil with a node light or a 12 volt led test light while cranking. Check for a signal at a fuel injector connector jack while cranking. If both these signals are missing. Ignition and fuel signals, then the problem may be some common point. My 've will loose both these signals if there is no crank shaft signal or position sensor. CPS is on rear of engine, on transmission bell housing. Check for connections of PCS.

these particular vehicles are almost always related to a bad cam\crank sensor,

have the crank sensor replaced this controls the spark and injector pulse it is located on the drivers back side of the engine above the transmission housing!

check ignition pick-up coil and ignition module

COULD BE THE TPS DROPPING OUT