Fuel boiling in carb - Page 2 - JeepForum.com

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post #16 of 45 Old 06-12-2013, 09:32 PM
superj
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Yes sir, that is what we are here for, ha ha ha. Just playing, I really don't help to much as I am not specialized to a certain model vehicle so I don't know the little secrets.


I don't feel like working on anything at this time so i sold my yj.
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post #17 of 45 Old 06-12-2013, 09:38 PM
laybackman
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If you are timed right and your TC is not too loose you are experiencing "pre vapor lock"

Did you add an exhaust header to this rig? That would do it.

Vapor lock is your gas vaporizing in the carb before it gets used because it is way too hot. At the drags the old 'fix' was a cool can filled with dry ice.

Try insulating the fuel lines in the engine compartment.

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
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post #18 of 45 Old 06-16-2013, 09:29 AM Thread Starter
jbrown73
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Started by wrapping the fuel lines first. Haven't driven it yet to see if that solved my problem. On a side note, discovered fuel boiling in carbs isn't that uncommon. I found on Camaro, Corvette, etc forums where they experience the same problem and it always related to the heat build up from the exhaust manifold. It wasn't specific to a manufacturer either as I read where Holley, Edlebrock, & Weber owners have had the same problem. All started by wrapping the fuel lines or rerouting them. I posted a pic of my engine compartment......enjoy & thanks for the suggestions!

image-2686041822.jpg

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Quote:
Originally Posted by Rproject View Post
The only thing I can say is to close your eyes. Seriously. If you close your eyes and pay attention to your finger tips, you'll be able to feel the nuts better and manipulate them easier.
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post #19 of 45 Old 06-16-2013, 10:36 AM
vadslram
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Vapor lock (fuel boiled in carb or lines) is very common in HP "V" configured engines. The carb is nestled nicely between two valve covers and doesn't get a whole bunch of air around it. On our straight 6s where the carb is hanging off to one side though there should be plenty of room for air to move around. keeping the incoming fuel cool by insulating should help but if it is bubbling in the carb you should do more to cool that. I read here where people disconnect the water to the intake mani but that will actually make it worse. If you have good coolant flow than your intake should never get hotter than 195 degrees, Without the coolant it can get way over 250.
Here is a thought, Try switching gasoline brands/ stations. Gas is configured differently depending on the season, grade and producer. If you look up boiling point of gasoline you'll find that the RANGE is 90 to 400! Huge swing! that's because they make it differently for different temperature profiles. Maybe you are getting a winter blend fuel that is supposed to boil/evaporate at a lower temp. Marine fuels and Higher octanes are configured for a lower temp too specifically so they aerosolize faster.
Worth a try.
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post #20 of 45 Old 06-16-2013, 10:53 AM
laybackman
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Another thought about your problem. Check your clutch fan to see if it is good. After you have fully heated this engine up and driven it for some distance, pull over and shut the engine off.

Pop the hood and attempt to spin the fan. There should be some resistance. If not that may be the cause of your heated fuel issue. The viscous clutch mechanism is dead and needs to be replaced. The viscous 'fluid' leaks out of the mechanism but never gets noticed.

Do you know what was good about the good old days? I wasn't good, And I wasn't old!

Senators and Congressman should wear uniforms like NASCAR drivers so we could identify their corporate sponsors....
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post #21 of 45 Old 06-16-2013, 11:00 AM
superj
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I neve liked fuel lines routed across an engine, like the yj 6 cylinders have. My karman ghia ha the lines routed like that and had horrible vapor lock trouble. Had to reroute all the lines along the edge of the engine bay to stop it

I don't feel like working on anything at this time so i sold my yj.
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post #22 of 45 Old 06-18-2013, 08:30 AM Thread Starter
jbrown73
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Drove her to work this a.m. and no fuel boiling so far. Will really get a true test this evening when I drive her home in the 90 degree heat.

"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government....." - Patrick Henry

Quote:
Originally Posted by Rproject View Post
The only thing I can say is to close your eyes. Seriously. If you close your eyes and pay attention to your finger tips, you'll be able to feel the nuts better and manipulate them easier.
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post #23 of 45 Old 06-18-2013, 11:16 AM
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glad its working so far.

I don't feel like working on anything at this time so i sold my yj.
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post #24 of 45 Old 06-18-2013, 05:58 PM Thread Starter
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Well, got home today only to discover fuel boiling in the carb bowl again. Only happens after the engine has been off for about 5 minutes without any air flow. Decided to check the timing chain slack as suggested earlier in the post........

Set the timing mark to 0 degrees with the dizzy cover off. Rotated the crank in the opposite direction and ended up with 16 degrees before the dizzy rotor moved. Did it three more times just to make sure and each time was the same.

I suppose that would have a considerable effect on power at highway speeds?
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post #25 of 45 Old 06-18-2013, 06:06 PM
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Quote:
Originally Posted by zeus87gn View Post
^^This^^

I had the same problem when I lived in Ga
Only I never routed it back thru the manifold
It ran lousy in the winter until it was fully warmed up
How much does the manifold heat jacket affect the warm up time/semi cold idle performance? Will it help the idle by 5 minutes or more or not. I have mine bypassed but it will run like crap until completely warmed up.

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post #26 of 45 Old 06-20-2013, 09:33 PM Thread Starter
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Lookie, lookie what i found when i pulled the timing chain cover off!! Maybe this is causing my excessive heating problem as suggested earlier in this post. will know for sure in a few days. will keep everyone updated!

image-2884056091.jpg

"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government....." - Patrick Henry

Quote:
Originally Posted by Rproject View Post
The only thing I can say is to close your eyes. Seriously. If you close your eyes and pay attention to your finger tips, you'll be able to feel the nuts better and manipulate them easier.
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post #27 of 45 Old 06-20-2013, 10:32 PM Thread Starter
jbrown73
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...."earlier in this THREAD"....lol

"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government....." - Patrick Henry

Quote:
Originally Posted by Rproject View Post
The only thing I can say is to close your eyes. Seriously. If you close your eyes and pay attention to your finger tips, you'll be able to feel the nuts better and manipulate them easier.
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post #28 of 45 Old 06-20-2013, 10:50 PM
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Don't forget to clean the oiling hole behind the cam gear when you have it off. The hole is usually blocked with crud on that age engine.

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #29 of 45 Old 06-21-2013, 05:43 AM
superj
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wowsers!!

I don't feel like working on anything at this time so i sold my yj.
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post #30 of 45 Old 06-21-2013, 06:42 AM
vadslram
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That's about right. Those nice nylon sprockets made the chain run quieter...right up until they self destructed.
What does the timing cover look like? Mine had a notch that looked perfect for a tensioner (there was none in any parts breakdown I could find) that was 3/4 worn away by chain slap.
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