Distubuotor Timing/Install 91 YJ 2.5 - JeepForum.com

 
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post #1 of 4 Old 02-11-2013, 06:01 PM Thread Starter
az_zoner
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Distubuotor Timing/Install 91 YJ 2.5

I'm in the process of getting a new/rebuilt engine going in my 91 YJ with a 2.5. The new engine is a 94. I've got it to a point that it idles at 800 rpm but once you open the throttle it bogs real bad. So I look at the timing with a light and the timing mark is way up beyond/before the 24 degree before mark. So I'm assuming that the distributor was put in a few teeth off. My questions is, if the distributor was put in correctly, what would the reading be on the timing marks? I know the ECU controls the timing but I'd just like to double check that I got it installed in the position. the Haynes manual that I have gives pretty good instructions for getting it in the correct position but like I said, just want to double check.

One more question. What is the best type of distributor wrench to get to the bolt? I have Brown Dog motor brackets and I can't get my hand even close to the bolt.

Thanks for any info,

Craig

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post #2 of 4 Old 02-11-2013, 06:55 PM
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Originally Posted by az_zoner View Post
I'm in the process of getting a new/rebuilt engine going in my 91 YJ with a 2.5. The new engine is a 94. I've got it to a point that it idles at 800 rpm but once you open the throttle it bogs real bad. So I look at the timing with a light and the timing mark is way up beyond/before the 24 degree before mark. So I'm assuming that the distributor was put in a few teeth off. My questions is, if the distributor was put in correctly, what would the reading be on the timing marks? I know the ECU controls the timing but I'd just like to double check that I got it installed in the position. the Haynes manual that I have gives pretty good instructions for getting it in the correct position but like I said, just want to double check.

One more question. What is the best type of distributor wrench to get to the bolt? I have Brown Dog motor brackets and I can't get my hand even close to the bolt.

Thanks for any info,

Craig
Pull #1 spark plug. Insert finger in #1 spark plug hole. Turn engine with socket and breaker bar until you feel a whoosh of air pushing past that finger in #1 cylinder. Remove finger and drop a long bladed screwdriver or wooden dowel into #1 cylinder. Slowly bring #1 piston up to TDC. That is where #1 piston is at its highest point. You are now at TDC on the compression stroke of #1 piston. Now check your timing marks. It should be at TDC also. And your rotor should be at or near #1 tower of your distributer cap.

If not something has moved or the distribute is in wrong. Or, you could have a jumped timing chain or a bad distributer gear. If the engine is running fine but the timing marks are way off then the harmonic balancer which is made in two layers has 'shifted'.

IF the timing chain has 'jumped' then the timed relationship between the crankshaft position (pistons) and camshaft position (valves and distributer) has been altered so timing is impossible.

Now mark base of the dist below where #1 plug tower is on dist cap. Next remove dist cap. Place dist in engine getting the rotor to point at the marked spot on the base of the dist or just before it actually. Once you have that tighten down the dist hold down bolt until it is tight but you can still turn the dist if possible. Slap on cap, and try to fire her up. You may need to move the dist some if possible until she does fire up. Then set your timing to whatever the specs are, IF possible. Sometimes timing is governed by the 'brain' and is not adjustable.



Now check your timing marks. It should be at TDC also. If it is not then the harmonic balancer has 'slipped' because of the two piece design and should be replaced IF you intend to use it to check your engine timing. It is not an absolute since your engine timing is managed by the brain and we are now confidant that your are at TDC mechanically.

Now determine where #1 plug tower is on your dist. cap while it is on the dist. Keep in mind the orientation of the dist. is governed by how it bolts into the engine, and mark the base of the dizzy. Pull the dist. and rotate the rotor to that mark. Holding the dist. shaft so it does not move flip the dist. and note the position of the slot for the oil pump drive shaft. Rotate the oil pump shaft to just before that position. Approximately 9:30- 10:00 o'clock or so IIRC.

Now before you stab the dist. into the engine you need to back off the rotor position a little. Where you start is not where the rotor orientation will end up because of the helical cut gears. The dist. shaft will have to advance some because of that gear design to end up in the right position. If you leave the rotor on the dist. you will see that advancing movement.

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post #3 of 4 Old 02-11-2013, 07:07 PM Thread Starter
az_zoner
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Thanks for the info. I've run some of your suggestions. My main questions is, what would the timing on the timing marks be if distributor was put incorrectly and the harmonic balancer has not slipped? Would it read 0 degrees (TDC) at 800 rpm? Or close to it?

thanks,

Craig
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post #4 of 4 Old 02-11-2013, 07:52 PM
uhohthe50
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I've ran into similar problems with my 4.2L. My timing marks are way off when I hook a timing light up to it. I have do the pull the plug and find the compression stroke trick to know when the #1 cylinder is at tdc but it didn't help. I ended up just timing it by trial and error until it was running the best. I know its not ideal but its the best I can get for now. Its running the best its going to. I'm thinking mine is the harmonic balancer too. How hard is it to change it? I just have never considered it since my jeep still runs good as is but it would be piece of mind if I could actually verify I have the correct timing for my setup.

My 1990 YJ Build Thread: http://www.jeepforum.com/forum/f22/might-well-start-build-thread-now-my-1990-yj-1291174/
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