Do I need a vacuum reducer???

[JeepFreak]

Well I'm trying to get my advance working before the weekend and I must say I'm stumped. My guess is that since they used the CTO in 78 that the CTO probably also acted as a vacuum reducer. Anyone following me on this. My AMX uses a vacuum reducer so I was thinking that maybe I might need to run one on the Chero. What it does is that it will hesitate and die when the advance is used. I tried to hook it up to none ported vacuum to see if I could get it to run but all she does is lope real hard then die. I am guessing that the Edelbrock carb is delivering a much stronger vacuum signal than the stock carb did. Anyone with a similiar problem? She runs fine without the advance hooked up.

[Veepster]

phew!!.....Whoa Nelly!! this sounds like a perfect time to say.........when you hear hoofbeats, think horses not zebras!

[JeepFreak]

Ummm, ok. I didn't quite get all that. :confused:

[Bob Barry]

The CTO does not reduce the amount of vacuum. Jeep did employ vacuum delay valves that kept vacuum from reaching its destination for a length of time. Such a beast would help on something like this vacuum-advance coming in too soon and causing the condition you describe.

What is your initial timing set at?

I don't think the new carb would produce dramatically increased vacuum signals.

[JeepFreak]

Humm. Well Bob the initial timing is set at about 13 btdc, but it likes to run at 15. Did a vacuum reading tonight and at idle I have 15 and at half throttle I have a reading of 20. Vacuum is steady with no jumping so I am ruling out the ole vacuum leak as a problem. It may be that I just have a funky dizy and need to try another. I have one on order for first thing in the morning so maybe it will make a difference. I did go get a reducer tonight and that did slow the advance. It stopped some of the problems but it still sputters when you hold half throttle. It is obviously a timing issue but is starting to get on my last nerve. Since I do not run the CTO on my rig this was why I asked the question of does it reduce vacuum. Just trying to use the laws of deduction. Just seems strange that it runs so well without the vacuum advance. I did add the lighter mechanical advance springs to get the advance sooner. If I could get it to run with the advance I would try to measure overal timing. I'm shooting for something in the area of 36 degrees of total advance @ 3,000 rpm.

[JeepFreak]

Ok well I got the new distributor in place and that did fix my advance problem. Im guessing the vacuum advance plate was not moving freely. So now I have vacuum advance and that is working properly now. Second problem is when I try to hold it at 3,000 she misses something aweful! Guess it's time for new cap and rotor. So the advance problem was probably a combination of a miss and a bad dizzy. Will keep you all posted(not that you care smile.gif).

[Veepster]

I am glad it worked out for you JeepFreak....my point was: it is usually something pretty simple! :cool:

[JeepFreak]

Well I'm still having trouble...When you put the motor under a heavy load it starts to cut out bad. I did the ignition upgrade today so all of thats good to go. It acts like it has a vacuum leak of some sort but none that I can find. I guess I will still keep plugging away at it until I get here figured out. Told my wife at about 5:00 this evening to go get me the baseball bat!

[andy d]

WE DO CARE,IT HELPS THE GENERAL KNOWLEDGE POOL OF THE BOARD IF PEOPLE POST THEIR REPAIR PROCESSES TO A SUCCESSFUL CONCLUSION. I OFTEN READ A THREAD, CONTRIBUTE IF I CAN, (MY ARM CHAIR DIAGS RUN ABOUT 60%) AND WAIT FOR A SOLUTION TO SEE HOW CLOSE I WAS. I BELIEVE I HAVE HELPED PEOPLE TO SAVE SOME TIME AND MONEY. I KNOW POSTS HERE HAVE SAVED ME TIME AND MONEY HAPPY LABOR DAY!

[JeepFreak]

YEEEEHAWWW!!!! She is alive! Well it took my entire labor day weekend to fix it but she is cured. Turnes out the problem was not of my creating and was one of the PO. Turns out that the distributor wires just below the plug had been patched at one time. My guess is that they were burned on the exhaust manifold. Well when the PO repaired the wires he connected the purple wire to the orange and the orange to the purple. He had to know what he was doing because he soldered them. Well this explained the missfires and rough idle. Veepster hit it right on the head when he said it was usually something simple. This was simple but hard to diagnose. I hope none of you ever have to experience the frustrations I just went through! Now if I could just explain why the PO crossed the wires first place. I was so close to ripping the motor out too!

Oh and I did wind up using a vacuum reducer for the vacuum advance!

[ September 03, 2001: Message edited by: JeepFreak ]

[Veepster]

a big heartfelt congratulations!!!!....I know that relief when the problem is solved!!!..Congrats Brother........