YJ Ignition problem

[entropy]

Originally Posted by CAPTAIN CNC

I just put a vacuum gauge on the manifold and got a steady 21 inches while idleing. If i punch the gas it falls to 0, the engine hesitates, then it climbs back upwards as the engine revs up and smoothes out. So i manage to disconnect the exhaust from the manifold and get the same results.

I then reconnect the exhaust and connect the gauge inbetween the distributor and carb. The gauge reads a steady 13 inches while idleing. If i punch the gas it falls to around 3-5 inches then back up to 13. If i gradually give it gas it rises to around 16-17 inches then back down to 13.

Now, correct me if i'm wrong, but shouldn't i have virtually NO vacuum at the distributor when idleing? And when i punch the gas it should jump up to or near the same vacuum reading as i got with the gauge on the manifold?

Where is the vacuum line connected? on the carb or the manifold?
When you have your safety classes on. with the engine running and the choke wide open look down into the top of the Carb and see if you can see the Pump shot... This is Carb'yd right?

[CAPTAIN CNC]

The vacuum line is connected to the base of the carb. It has always been connected there.

I can see the pump shot every time i hit the gas. Steady consistent stream every time.

[entropy]

Ok...

Originally Posted by CAPTAIN CNC

I just put a vacuum gauge on the manifold and got a steady 21 inches while idleing. If i punch the gas it falls to 0, the engine hesitates, then it climbs back upwards as the engine revs up and smoothes out. So i manage to disconnect the exhaust from the manifold and get the same results.

This sounds normal for manifold vacuum readings; and exactly like a missing, to small, or off timed, accelerator pump shot.

Originally Posted by CAPTAIN CNC

I then reconnect the exhaust and connect the gauge inbetween the distributor and carb. The gauge reads a steady 13 inches while idleing. If i punch the gas it falls to around 3-5 inches then back up to 13. If i gradually give it gas it rises to around 16-17 inches then back down to 13.

13" at idle on a stock engine is about 5" low indicating that the engine is worn out, or has a vacuum leak someplace you should have about 18" at idle.

Originally Posted by CAPTAIN CNC

Now, correct me if i'm wrong, but shouldn't i have virtually NO vacuum at the distributor when idleing? And when i punch the gas it should jump up to or near the same vacuum reading as i got with the gauge on the manifold?

If you are connected to a ported vacuum source then yes if a manifold vacuum source then you will have what you describe. There should be a sticker showing vacuum routing and or in the shop manual, and certainly in the web someplace...

[CAPTAIN CNC]

Ok... having said that i'm now down to either a vacuum leak (already checked but certainly could have missed or never found) or the engine itself is worn out. Sooo, I guess i'll go out and check compression on each cylinder.

While i'm doing that... Can i be losing vacuum through the brake booster somehow? I dont hear anything and the brakes seem to work fine. If i unplug the booster and plug the line would this be effectively eliminating the booster as a source for a leak?

[CAPTAIN CNC]

Compression reads as follows. From back to front...

#6 127
#5 127
#4 135
#3 133
#2 131
#1 140

So where the HELL is this flipping VACUUM LEAK! I'm outta starting fluid. What else can i check for leaks with?

[CAPTAIN CNC]

Well aren't i just an ass. Gosh i feel like a dunce now. The jeep starts, runs, drives great now. I'm REALLY hesitant to even say what the problem is because of how stupid it makes me look but for the sake of others running into this problem someday i want to make it known what i did wrong. This is what happened:

When i set the timing i looked at the VECI label under the hood for the rpm to set it at. Normally i have the hood on the prop stand when i'm working on it but as this has been an ongoing problem the hood has been up against the windshield. Standing on the ground it appeared to read 1000rpm so thats where i set the idle when i was setting/checking the timing. Frustrated with just everything that has unfolded this past week or 2 i walk BACK out to the garage and decide to try and wipe my memory clean of ANYTHING i had done in the past and begin evaluating the engine as if it were the first time. So i walk out and just as i was about to turn up the idle to 1000 rpm i says to myself "1000 rpm... nah i can't assume i remember correct... i gotta look for myself just like i had NEVER been under this hood before". So i walk around the side and yes it looks to be 1000. I pull the hood down on the prop rod and get up on the bumper on my knees and wipe the label clean and it reads 1600. "1600!!!... WTF am i thinking 1000 for?" Suddenly a fire is lit under my ass. A glimmer of hope. I'll be it a stupid brainfart glimmer but a glimmer none the rest. So i set off quickly to increase the idle speed and reset the timing. It is grosely retarded. I get it set to about 9-10 degrees at 1600 rpm and pull off the timing light and reconnect the vacuum advance. I hit the throttle a few times and it sounds a world better. I hop in the jeep, throw it in reverse and punch the accelerator and the tires chirp coming outta the garage. With anticipation building further i pull out into the road and head towards a hill. Up the hill the jeep continues to pull hard. It starts quick, idles great, runs great, and pulls hard under a load. And why wouldnt it with the timing set correctly now.

Geez do i feel like an idiot. I dont know when or how i ever got that figure of 1000 rpms in my head but you can see just how much grief i have caused myself. Hopefully someone else will learn from my lack of clarity on this issue and i want to personally appologize to all who have been helping me for unknowingly posting the wrong information. I kept on saying "the timing is right on", "the timing is dead nuts". And that was far from the case.

Thanks again to everybody who has helped me, especially Entropy. I know it must have been frustrating to see me squirming with seemingly so many problems especially only to find out my dumb ass wasnt setting the timing correctly. And i too am very frustrated with myself but at this point a fix is a fix and i'm happy to accept it no matter what form it comes in. The damn jeep running great again far outweights the stupidity i have exibited in my opinion. I'm soooo tired of messing with it. And what do you wanna bet i will not make this mistake again in the future.

You may commence laughing histerically at me now. Ugh.....

[gearheadmb]

I'm glad you found it! Miller time.