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Unread 11-24-2013, 01:01 PM   #1
Blubberpenguin
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Engine Issues CJ5 AMC 304

I have a 74 CJ5 that has been I picked up as a project a couple years ago and am just getting some free time to work on. When I bought it, it ran really rough and the carb was junk. After trying to swap the carb with a refurb that leaked I decided to go ahead and get an edelbrock Performer non-egr manifold and a Holley truck avenger 670 cfm carb. As a note I have also replaced the plugs, wires, coil, and rebuilt the top of the distributor (cap, points, rotor). The jeep will fire up fine when cold and idles good until it gets warm. Once it gets warm it starts running rough almost like it is skipping a cylinder here and there. At any time whether it is idling rough or good, if I put it in gear and try and drive it will stall. I have pulled the first plug and checked to make sure the timing is close. I have a timing light but can't use it because I can't get the idle to back down below 1300 RPM and have the idle screw all the way out. I am running manifold vac to the distributor off the bottom of the carb. I have used carb spray to check around the carb base and the plugs in the manifold for vacuum leaks but have found none. I have read it is common to not get a good seal when installing the manifold which could cause a vacuum leake under the manifold. Before I pull the manifold off and try and reinstall I figured I would post this to see if anyone has any other suggestions. Let me know what you guys think and I will check it out and let everyone know.

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Unread 11-24-2013, 07:55 PM   #2
cruiser54
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Sounds like a vacuum leak combined with a few other things.

How did you set the timing? No light? Vacuum hose should go to ported vacuum higher up in the carb for best performance.
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Unread 11-24-2013, 08:27 PM   #3
Blubberpenguin
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Quote:
Originally Posted by cruiser54
Sounds like a vacuum leak combined with a few other things. How did you set the timing? No light? Vacuum hose should go to ported vacuum higher up in the carb for best performance.
I set the timing initially by pulling out the spark plug in cylinder #1 and spinning the crank shaft pulley by hand while a buddy made sure it was the compression cycle. Once we knew it was on the compression cycle we took the cylinder up to TDC using a long screwdriver in the plug hole to feel when it got to TDC. 1st cylinder TDC matched the mark on the vibration damper on the crankshaft. Once I got it to TDC I pulled the distributor cap to see where the rotor was aimed and adjusted the distributor so that the plug 1 location on the cap matched up with the rotor location.

Can't set the timing with the light because I can't get the RPM to back down to the range to match up with the manufacturer specs for setting timing.

Did a bunch of reading on connecting distributor advance to ported vs manifold vac. Have tried both and it runs better on manifold vac.

What are the few other things you think it could be?
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Unread 11-24-2013, 09:22 PM   #4
jkbulldawg
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Takethe fuel line loose and turn the motor over and see how much fuel ur fuel pump is throwing. It should shoot it about 7 to 10ft. If its good i would check all fuel filters some of them cj's had filtets on the frame rail and the tanks are nitorious for rust. Could b trash.
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Unread 11-24-2013, 10:07 PM   #5
cruiser54
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If it runs better on manifold vacuum, your timing is retarded at the dizzy.
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An index to over 25 write-ups can be found in Post #1.

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My Jeep Technical Photos

http://www.cherokeeforum.com/g/album/1725214
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Unread 11-25-2013, 05:52 AM   #6
Blubberpenguin
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Jkbulldawg-I will check fuel pressure but I have a new filter on that you can see right before the fuel line ties into the carb and it is staying full and fuel looks clean. I'll post what the pressure is after I check.

Cruiser- how can you tell the timing is retarded if it runs better on manifold? I will switch back to ported and adjust the dizzy some so that it should be advanced and see it that helps bring the RPM down to where I can get a timing light on it to adjust. As another note I left out of my original post, when I replaced the dizzy upper parts, I adjusted the points by checking the dwell angle and it's in spec now (subject to adjustment after I mess with the dizzy and ported vac). Will let you know results after I test it out (May be a day or 2 before I get to it, gotta love Mondays)
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amc 304 , cj5 , rough idle , vacumm leak

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