Here is a write up I put together to attempt to help anyone who pulled their distributor and now got a bit confused.
Pull #1 spark plug. Insert finger in #1 spark plug hole.
Turn engine by the harmonic balancer bolt head with socket and breaker bar until you feel a whoosh of air pushing past that finger in #1 cylinder.
Remove finger and slide something long and thin like a piece of straightened coat hanger or thin wooden dowel into #1 cylinder.
Now, SLOWLY bring #1 piston up to TDC. Watch that coat hanger or dowel. Once you feel the whoosh of air and the piston is at its highest point this engine is now at TDC of the compression stroke.
Now check your timing marks. They should be at TDC also. Pull your distributor cap. Your rotor should be at or just before #1 tower of that mark you made noting the position of #1 tower on your distributor cap.
If not, something is not right….obviously. That could be a jumped timing chain, or a bad distributor gear. If the timing marks are off but it runs fine then the most likely culprit is the harmonic balancer which is a two piece affair has had the outside layer ‘slip’ so the marks are off but the timing is correct.
If your rotor is not where it should be and everything else is OK pull the distributor.
Note the position of the tab on the bottom end of the distributor shaft. It has to fit into the slot of the oil pump drive shaft.
Note the cut of the drive gear for the distributor. They are helical cut (slanted). You have to 'guesstimate' where that slot should be when you are installing the distributor. For a Jeep 4.0 that would be at the 11 o'clock position if you are standing by the passenger's side fender, the right side of the engine, facing the engine.
Your rotor should be roughly pointed at the 9 o'clock position when you start to slide the distributor in. Keep in mind that the rotor will turn some and end up aligned with that oil pump drive shaft. Also the slot for the hold down bolt will be aligned.
Just ahead of where your rotor is pointed is #1 position for the distributor cap.
Note that position and then add the plug wires in the proper firing order. For a 4.0 it is 1 5 3 6 2 4.
Slap on cap, and try to fire her up. You may need to move the distributor some if necessary and use a timing light to set the time BUT on the newer engines timing is governed by the 'brain' and is not adjustable.
Do you know what was good about the good old days? I wasn't good, And I wasn't old!
Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....