I had my 4.0 all torn down chasing a tapping noise (believed to be bad lifter) and while i was in there I decided to go ahead and treat myself to a Lunati Voodoo cam and a new timing set just to eliminate all variables. I went with the mild cam (circa 500 lift both ways) so as to avoid binding the valve springs and to retain my low end grunt for the rocks. I had to buy a timing set for a 1975 Cherokee (just used it as reference so Autozone would sell me a timing set for the older style cam nose) and rob a "spring and pin" style retainer to make the cam work. Everything went together easy as pie until i tried to start the jeep for break-in... no luck. It cranks like normal for a minute and then begins to intermittently "pull down" here and there like something is out of time or it is attempting to fire way too early. every once and a while this yields a cough from the exhaust but no real firing action yet.

sounds like: rraa-ka-ka-ka-ka-ka-pwuuaaahh-ka-pwaaahh-ka-ka-pwuuaaahh-ka-ka-ka-pwuuaaahh-pwuuaaahh-ka-ka-ka

I have several questions before i am totally out of ideas:

would the firing order of the 2001 l-6 be the same as that of an old l-6?
(just making sure the cam is ground for the correct firing order)

would there be some reason why my cam position sensor would be incorrectly interpreting the position of this new cam? The drive gear for the sensor and oil pump was right where it should be and it all looked the same..

on the heels of that, my cam position sensor doesn't have anything to "index" it.. how does one know when it is in the right position? i had never pulled one before and didn't even think to note it's original position, assuming it would only go in one way. the body of the sensor had a flat spot but the hole in the block is just a circle, the sensor can be turned any way you want and re-fastened. is this a method of "setting the timing"? (even though it's computer controlled) if so there are no marks...

i am 99.9999% sure the cam is correctly timed, i checked and re-checked and re-checked that then turned it over and re-checked that (you get the idea) and the assembled everything else per the books..

other things to note:

cranks normally when injectors are unplugged

i'm relatively savvy so feel free to use big words, any help is greaaaaatly appreciated!

 

you have to index your cam position sensor. Check this video out, it explains how to do it easily.

 

thank you, I feel like an idiot for just slapping that back in without any indexing. I already have it together but i guess i can use the timing marks to find TDC. just gotta figure out which TDC is bang and which is whoosh

 

Just did this this morning. You'll need a friend to help out. Pull the cylinder 1 spark plug. Hold you thumb or finger over the spark plug hole while said friend turns the engine over by hand using a socket on the harmonic balancer bolt. When you feel pressure build up in the cylinder then stop turning. Line up the mark on the harmonic balancer with the 0 mark on the timing cover then you are ready to index the cam sensor.

 

He explained it in the video.

To be more clear for you, the piston is at the top position (TDC, Top Dead Center) twice, once for "Bang" (the Compression stroke), and once for "Whoosh" (the Exhaust stroke.)

Stick your finger in the #1 spark plug hole, just like the guy said. You'll only build pressure on the "bang" stroke, because the "whoosh" stroke is for exhaust, and the exhaust valve will be open. You will not build pressure during "whoosh."

Does this make sense?