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  #1  
Old 04-27-2000, 04:18 PM
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Default wood a vaccuum leak cause engine to bog

After getting my cj-5 all put back together, I decided to take it for its madden voyage. Even though the engine idles as smooth as ice, as soon as take off, it starts to bog something fierce. I noticed some disconnected vaccuum lines. Could this be causing it. I also had previous trouble with the firing order. Could I have the firing order off 180 degrees and still idle good? I'm running out of time with this. Have to have everything 100% in a couple of days. Thank you oh yeah, its a 304 with holley carb.

Keith

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Old 04-27-2000, 08:29 PM
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Default Re: wood a vaccuum leak cause engine to bog

A V-8 will barely run with the distributor out 180 degrees.
It will pop and backfire something fierce...

If the bog is when you first hit the throttle trying to take off, it sounds like the accelerator pump isn't doing it's job.
If you take it out on the street, set completely still, and stomp the throttle, and it bogs or dies, it's a good chance it's the accelerator pump.

It may be the power valve...

Vacuum leaks will lean the vehicle out so bad that it does stumble, but usually not kill it...

TESTS...
1. Take a vacuum reading from the manifold vacuum. (Not the pvc line)
Take one at idle, and take one when it bogs...

2. Plug all those vacuum lines, and try it.
If the bog goes away, you found the problem...

3. BE CAREFUL WITH THIS ONE...
Take a can of carb cleaner or starting fluid...
One of those with the little tube you can attach to the spray head...
Spray all around the base of the carb, the ends of the throttle shafts, and around the seams where the intake manifold meet the heads.
You are listening for the idle to go up. If it does, you found the leak...

4. Take the air cleaner off, and look down the carb throat.
Snap the throttle linkage back fully with one smart movement.
Watch the accelerator pump discharge nozzles (shooters).

If the fuel stream doesn't come out in a nice, bubble free stream and hit the venturi boosters, you have a problem.
If the fuel has bubbles or is weak, you have a problem.
If the accelerator pump stroke doesn't last until the linkage is all the way back, you have a problem...

The fuel is supposed to come out in a nice, strong, clean stream and hit the venturi boosters (the little round things sticking out in the venturi bores).
The pump shot should last the entire time you are moving the linkage back.

Don't do this a bunch of times with the engine off.
It floods the engine, and washes down the cylinder wall, and contaminates the oil...
A few times, (two or three) won't hurt anything...

Let me know what you find, and we'll take it from there....

"I Have The Body Of A God... Buddha"
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Old 04-27-2000, 08:48 PM
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Default Re: wood a vaccuum leak cause engine to bog

IM guessing maybe your vacum advance is one of those unhooked vac lines..

make sure its hooked up!
my AMC 360 did this once, I got on it REALLY hard and the fan blew off the vac line from the distr.

it was dead mushy off of hte line like this

OzarkJeep
77 CJ5, in a bunch of sanded and primered pieces
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Old 04-27-2000, 09:15 PM
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Default Re: wood a vaccuum leak cause engine to bog

You are correct Ozark, that never occured to me.
I always assume that if you are running a Holley, you have the ported vacuum hooked up to the distributor...

I should learn not to assume anything here...

Still need more information before we can track it down...
If it's an off the line stumble, it's probably carb,
If it's a cronic problem not gaining rpm, it may be any one of a dozen ignition problems...

I'm interested in knowing what those vacuum reading are, and if the accelrator pump is working or not...

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Old 04-27-2000, 09:33 PM
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Default Re: wood a vaccuum leak cause engine to bog

Ive never had those carb troubles so I cant compare, where the actual stumble occurs is not described well enough for me to even guess, you know more about that, and what those vac readings should be.
I didnt cover the acc pump, simply because you did such a good job already!


but Ive got an AMC V8, and ive felt it loose all its balls right off idle without that little line atttatched!



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Old 04-27-2000, 09:53 PM
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Default Re: wood a vaccuum leak cause engine to bog

at idle, there is no hesitation. While in neutral, if I whomp on the gas, the exhaust gives a big fart. While driving, it feels like i'm running out of gas. The vaccuum advance on the distributor is hooked up. hmmmmmmmm I know the line is kind of soft. Maybe there is actually a leak in that line. It went on kind of easy with no resistance. Thanks for the replies

Keith

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Old 04-27-2000, 11:07 PM
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Default Re: wood a vaccuum leak cause engine to bog

Sounding more and more like accelerator pump problems...

Do all of the other tests I laid out, and jot down every time it does it...

If it is the accelerator pump, every time you give it gas, it will hesitate or outright fall on it's face.

Keep us posted...

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Old 04-27-2000, 11:12 PM
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Default Re: wood a vaccuum leak cause engine to bog

what is the timing set at? and how did you set it?

you need to do alot of things here, plug all of those vac hoses for starters, then test the acc pump as teamRush suggested, just look down the carb while you stroke the throttle, it should mist smoothly



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Old 04-28-2000, 08:20 AM
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Default Re: wood a vaccuum leak cause engine to bog

I'm having this same problem with my 74 CJ5. Actually, it was running like a champ until I changed out the valve cover to eliminate an oil leak. Now it boggs down really bad, but sporadically.

So.. Aaron, I have a couple questions for you on this one.

First is that my Jeep has been totally stripped of all its emissions equipment. What I mean is that there's one line from vacuum advance to a hole on the carb and a line from the PCV to the intake manifold. That's it! I know there should be other lines coming in from the crankcase to a router, stuff like that, but it's all gone. How does this affect the timing of the vehicle and would this cause the engine to bogg down?

Second. Is it possible for there to be an excessive oil pressure problem? For instance, what if my valve cover was leaking because the engine was trying to push oil out of somewhere? I don't even know if this is possible, but it makes some sense in my case. The engine still leaks, just not at the valve cover anymore. (I'm still trying to figure out WHERE it's coming from). Anyway, point is, if the engine had too much pressure (is this possible?) and it was forcing oil out of the only place it could, the valve cover, and now that hole is plugged up, could it be screwing with some other part of the engine and causing this symptom?

This weekend I'm going to get some new vac. lines and I'm changing out all the ignition stuff just to make sure, new cap, rotor, points, coil, wires, plugs, etc. Then it's going to the shop if it still has a problem. I'm pretty sure this is all related to timing, but I've learned that it's not always what I think!!! I know the vehicle needs a tune up and the timing is way out whack anyway, runs real rich, occasional backfire, stuff like that.

TIA for replies guys.

Carl, Tampa, FL, 74 CJ-5
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Old 04-28-2000, 10:50 PM
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Default Re: wood a vaccuum leak cause engine to bog

Well I found the answer. (by accident) While troubleshooting all that was suggested (with no luck) I happen to notice a spark out of the corner of my eye. I thought it was just my imagination. but after a closer look, I noticed that the connections on my resister (i think thats what its called) where barely hand tightened. I immediatly shut her down tightened the screws, and magic, its running like a champ again. Thanks for all the suggestions guys.

Keith

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