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Timing a 4.0L
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
Thanks
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Registered User
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'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.
Registered User
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.
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Registered User
Quote:
Originally Posted by veritas4156
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.
Registered User
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.
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.
Quote:
Originally Posted by Alfons
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'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.
Bikini Bridge Inspector
Quote:
Originally Posted by Alfons
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'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.
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!

Registered User
Quote:
Originally Posted by laybackman
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!
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!

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.
Registered User
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.
Registered User
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 going out of town with the girlfriend so I guess theres always Monday...
Registered User
Quote:
Originally Posted by veritas4156
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 going out of town with the girlfriend so I guess theres always Monday...
Registered User
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.
Registered User
Quote:
Originally Posted by veritas4156
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.
Registered User
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.
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.
Registered User
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?
Registered User
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...

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...

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