Strange timing gremlins... - JeepForum.com

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post #1 of 91 Old 04-28-2015, 10:24 AM Thread Starter
XLarge
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Strange timing gremlins...

He story goes like this:
All was good then i stopped with the cj7 for a rest. After starting again I suddenly felt a strong hesitation while accelerating. The next morning I was not able to climb that little street to work because of severe hesitation and lack of power.
I began to check the standard things.
Gas filter clean. Spark at every pot. Dizzy firm (!) but... Wait a minute... The timing was 0' where it was about 8' btdc before. I'm sure about this (with vacuum unplugged and capped). I set it with a timing light weeks ago.
So I cleaned the dizzy, readjusted it to 9' btdc and hooked the vacuum (manifold).

It ran like a champ.

Now again suddenly things are running bad again.
Hesitation, no power...
Checked timing again without vacuum. It's still 9' but when i slowly Rev the engine I can see it going down in the beginning to 3-4' btdc. At 1500 rpm it rises again.
Is this normal?
When coming back to idle it seems to jump first staying about 16' and the suddenly falls back to 9'.

I have a hei dizzy from eBay and I reused the original gear of the motorcraft dizzy.
If I apply vacuum to the vacuum-advance it acts normal going up to 24' in idle.

No vacuum leaks.

Dizzy gear?
Timing chain?
Dizzy gone?

Any help appreciated.

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post #2 of 91 Old 04-28-2015, 10:29 AM
TIPPEDITOVER
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Almost acts like it's on ported vacuum instead of manifold vacuum. Also seems like the flyweights aren't working correctly. That's all I have right now and it might not have anything to do with the problem.

Stuttgart? I went to a Metallica concert there in 98'. Was awesome.
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post #3 of 91 Old 04-28-2015, 10:32 AM Thread Starter
XLarge
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But is there any vacuum that can actually retard the timing... It does the same thing even without vacuum hooked up.
I have an easy one wire setup of the dizzy, nuttered, ecm eliminated.
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post #4 of 91 Old 04-28-2015, 10:36 AM
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Like I mentioned before the flyweights could be involved. I'd make sure they move freely and aren't binding up throwing the curve off.

But also make sure your vacuum advance is on pure manifold vacuum. It's probably on ported vacuum to pass emissions. You said you saw the timing go up to 24* when you applied vacuum by hand, so it's not froze up. Put it to manifold vacuum.
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post #5 of 91 Old 04-28-2015, 10:36 AM
Mike Romain
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Another poster just had his advance plate seize up, but that was on an old distributor. Sounds like your weights have issues. If you grab your rotor does it twist a little one way only under heavy spring load?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #6 of 91 Old 04-28-2015, 11:29 AM
gmakra
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How many miles on the engine?
If its high mileage Im leaning to a timing chain issue.
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post #7 of 91 Old 04-28-2015, 12:07 PM Thread Starter
XLarge
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Would this explain the strange 10' jump in timing with the dizzy definitively not loose?
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post #8 of 91 Old 04-28-2015, 12:19 PM
swatson454
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I'd pull the rotor off and have a look-see at the springs. It may have been assembled with really light springs "for more torque and horsepower". If it's got light springs in it, I'd switch one out for a medium spring and see if the timing becomes more stable.

Do you know what rpm the centrifugal advance maxes out?


Shawn

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post #9 of 91 Old 04-28-2015, 01:11 PM
gmakra
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Quote:
The timing was 0' where it was about 8' btdc before. I'm sure about this (with vacuum unplugged and capped). I set it with a timing light weeks ago.
So I cleaned the dizzy, readjusted it to 9' btdc and hooked the vacuum (manifold).
Shawn how would weak springs go to 0 degrees?
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post #10 of 91 Old 04-28-2015, 01:17 PM
swatson454
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Quote:
Originally Posted by gmakra View Post
Shawn how would weak springs go to 0 degrees?
By not fully retracting the weights and lying to him the first time he set the timing. I've seen it before; the timing seems to be different every time you throw a light on it.


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post #11 of 91 Old 04-28-2015, 01:42 PM Thread Starter
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I'll check that tomorrow. But the really strange thing is the fact that it ran very good 1 hour before...
Miles are unknown.
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post #12 of 91 Old 04-28-2015, 02:55 PM
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There are a couple of things you can check for while you have the rotor off:

See if the whole thing is packed full of red dust. Remove the little c-clips from the posts so you can pull the cam and weights off and see if you find any evidence of arcing.

I had an Accel "Blueprint" HEI that basically welded itself together. That was before I learned to leave the marketing hype where it belongs and reduced my plug gaps down to .040 regardless of what coil I ran.

Pics are always great, too.


Shawn

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post #13 of 91 Old 04-29-2015, 12:56 AM Thread Starter
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Ok, I can turn the rotor clockwise quite a bit freely, counterclockwise I feel the springs and I can turn the rotor just few degrees against the springs.
If I'm at 0' at the balancer the rotor points straight to #1. I can see movement in the rotor at approx. 12' on the balancer if I turn it by hand.

I think this is ok for the timing chain?

One thing I realised is, that if I turn the rotor counterclockwise against the springs it lifts a little bit and on the end of the movement I can push it down again.
So there is play (in/out-wise) of ca. 2-3mm. Does this mean that I should shim the dizzy a little bit higher?

Perhaps the dizzy cam lifts on acceleration an retards my timing?

Otherwise it looks very clean and everything moves as it should be.

Gtx from Germany
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post #14 of 91 Old 04-29-2015, 03:55 AM
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Quote:
Originally Posted by XLarge View Post
Ok, I can turn the rotor clockwise quite a bit freely, counterclockwise I feel the springs and I can turn the rotor just few degrees against the springs.
If I'm at 0' at the balancer the rotor points straight to #1. I can see movement in the rotor at approx. 12' on the balancer if I turn it by hand.

I think this is ok for the timing chain?

One thing I realised is, that if I turn the rotor counterclockwise against the springs it lifts a little bit and on the end of the movement I can push it down again.
So there is play (in/out-wise) of ca. 2-3mm. Does this mean that I should shim the dizzy a little bit higher?

Perhaps the dizzy cam lifts on acceleration an retards my timing?

Otherwise it looks very clean and everything moves as it should be.

Gtx from Germany
unless I'm reading this wrong, you're trying to check the slack in the timing chain by moving the rotor?

to check the chain slack, you should be turning the crankshaft and watching to see when the rotor moves. then turn the crank the other way and see how many degrees it turns before the rotor moves back.
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post #15 of 91 Old 04-29-2015, 04:15 AM
Mike Romain
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12 on the timing chain using the balancer marks is fine so the chain should be ok. The last couple new chain and gear sets I put in had 15 of slop.
Your distributor sounds shot though. There should be no up down and it should only move one way when twisted.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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