Alright I know you're not supposed to retime a 4.0L but the guy that I bought my Jeep from tried to time it and messed it up. Anything special to look out for or just time it like any other vehicle?

Thanks

The distributor needs to be set up properly, then the ECU handles the rest of the timing, but the initial setup is very important. In my opinion, the easiest thing to do at this point would be to pull the distributor out and to set it up properly, then at least, you've got a fighting chance of getting the engine to run right. Here are the pertinent two pages from the factory service manual that describe how to set up the 4 liter distributor. You need to pay attention to where the rotor needs to be when the engine is rotated to TDC, so the "scribe mark" described on the first page is very important.





I'd also recommend that you invest in some type of manual to give you a hand in understanding and maintaining your jeep. The Haynes manual is normally the easiest and cheapest to get - the stuff in my pics is also described in the Haynes manual.

i have a haynes, I just know that they have been known to be wrong sometimes, thats why I asked here. The other reason I asked here is because the timing cover was removed from my jeep, and the timing was messed with down there. The haynes manual made it seem too simple, compared to most cars. The manual doesnt even mention to use a timing gun.

If you know that things were changed under the timing cover & you're not happy about it, then you should have a look. It's relatively simple to see whether everything's OK there or not & the Haynes manual covers the gear setup & chain tightness. something you'll need to consider will be; a new gasket for the timing cover and a new front oil seal (this fits into the timing cover). You don't need a timing gun because you don't use it to adjust timing, you do the distributor setup physically & the ECU does the rest digitally - the distributor is firmly bolted in place. I do use the timing light to ensure that I haven't installed the distributor one tooth out in the retarded direction - if you're one tooth out in the advanced direction, you won't start the engine.

Very good info.
Very few people outside of the Jeep Tech's have any idea how important the rotor to distributor body placement is.
Most people assume you can just turn it to set timing.
It is a unique setup.

That works for an undisturbed distributer or an engine that has not been disturbed.

First off check your timing with a timing light.

If you don't have one then here's anothe way of checking engine timing out:

Pull all your plugs so the motor can be turned by hand easier. Using a large socket and breaker bar turn the motor over until while your finger is in #1 spark plug hole. Get a friend to help you. As the engine comes up on TDC of the compression stroke you will feel pressure on your finger (compression!)
Now at the top of that stroke your engine will be at TDC on the compression stroke. If your TDC mark is not aligned with the pointer then the timing chain set is messed up somewhow and your pointer is now pointing at the new TDC mark on your harmonic balancer wherever that might be. Mark it well so you can find it later on.



Now mark the dizzy body where the #1 spark plug tower is on the dist. cap. Now remove the cap. The rotor should be about to go by the mark you made on the body of the dist( #1 sprak plugtower on the cap). If it isn't then your dist. is probably in wrong.

If you have determind that the dist is in wrong:

Now you have to pull the dist. with the rotor inmplace and get the rotor aligned just before that mark on the dist body you made earlier ANd you have to get the dist shaft aligned with the slot on the oil pump to drive it AND you have to deal with the curved gdrive gear on the cam shaft that will not allow you to just drop the dist in the engine it has to be 'backed off' some. If any of this does not make sense to you get help. I hope I didn't scare you off or anything but if you can not visualize what these moving parts are doing relative to each other, then I would get help. Lot od luck on your project!

The procedures I posted cover the distributor removal & installation whether it's been previously disturbed or not. Following the steps on the first page will show you whether the distributor is already seated properly or not - the scribe mark here is important, it's not just marking where #1 cap post is, it's marking the LEFT SIDE of the cap post (this is described by step 3). Also, the rotor must be positioned with the trailing edge on the scribe mark (step 6) - just gone PAST the post. If you don't have the engine at TDC and the distributor rotor in the position described, it will most likely be retarded - hard to start and will miss as the engine rpm increase (assuming the timing gears are set up properly) - there are heat consequences as well to running it retarded because there are still flames in the cylinder when the exhaust valve opens causing the manifold and pipe to "glow" after a few minutes . If the distributor is already set up according to the description, there's no need to pull it & your problem is most likely elsewhere. I added the second page to provide re-installation instructions - after re-installation, the rotor should be in the described position with the engine still at TDC. If everything else is good, it should start with no effort.

Not following the setup precisely will normally give you enough "slop" in the counterclockwise direction to convince you to drop the distributor in one tooth retarded. The distributor has only 13 teeth, so a single tooth mis-alignment is between 27 and 28 degrees, and one tooth retarded will cause #1 cylinder to fire close to 10 degrees BTDC (before TDC) - I've checked this with a timing light only, so I may be off by a couple of degrees one way or the other. One tooth the other way will move the firing so far advanced that it really shouldn't start at all.

Thanks guys. The timing was definitely messed with by the PO. His crank position sensor went and he redid everything in the ignition system trying to figure it out, then replaced the CPS after the time was off. So I'll be doing the timing tomorrow, I'll let you know how it works after I'm done.

Well here's an update... I pulled the crank pulley off and the bolts from the puller broke the timing cover in half. So in short I spent the whole day ripping apart a cherokee in the junkyard to get the damn timing cover off.

I'm going out of town with the girlfriend so I guess theres always Monday...

I'm intrigued as to how you got the puller onto the timing cover. You need a harmonic balancer puller to remove the "crank pulley" - DON'T use a regular puller or you could pull the balancer apart (the pulley part is joined to the drive part with rubber & will come apart). The harmonic balancer puller looks similar to a steering wheel puller.

yeah i used one of those, the one shaped like a peace sign without the circle, that you thread the bolts into the pully with. thats what it said to use in the haynes manual i believe. if its the wrong one then i guess i messed up. i should be orking on the jeep either tomorrow or tuesday.

That's the right one, good luck.

So I redid the timing yesterday, got the new timing cover 90% of the way on, and then called it a night because I had been working on it in the snow outside in 15 degree weather for 7 hours with one of those lights that strap around your head because it got dark about halfway through. Today I'm going to reposition the distributor and hopefully everything will start right up. Turns out the camshaft mark and the crankshaft mark were about 1 cm away from each other at TDC. Now they're perfect... I think.

That oil pan to timing cover rubber gasket was the biggest pain in the *** to work with. Apparently some timing covers have holes so that the gasket threads in(like my old one) and some do not(like the new one). Took me two hours to get the new one in.

Maybe it's a bad time to ask, but when you had the cover off, did you check the tightness of the timing chain? And the gears for wear?

Heh finally I feel good about myself with regards to my jeep. When I took the cover off I decided if I was gonna do this much work I'm gonna replace the gears and chain

On the other side of the spectrum, I did all the timing stuff(perfectly I believe) and it still doesn't start. If I floor it while cranking then it backfires. And by back fire I mean a plume of FLAMES out the intake. I'm beginning to think I bought a Heap not a Jeep. I'm gonna try changing the computer tomorrow in case the computer is messed up. Unless anyone has any other ideas...