SBC fuel issue? Vaporlock? - JeepForum.com
 
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post #1 of 10 Old 06-08-2018, 09:33 PM Thread Starter
ReedJeepster
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SBC fuel issue? Vaporlock?

Alright everyone...I have an issue. 78 CJ7 w/SBC (I know some are cringing right now&#x1f61d Anyways, the motor has a mild cam other then that it is pretty stock. I am having an issue with it acting as if it is starving for fuel after about 5-10min of 10mph or less. Seems like vapor lock issue to me but I have braided 6 fuel line from tank to mechanical pump and from pump to carb. Temp gauge doesnt get above 190 but it will cut out and die like it doesnt have fuel. I do not have a return line but my fuel line doesn't seem to be hot. It isnt anywhere close to headers or exhaust. Driving down the road doesnt seem to be an issue, only while crawling through trails or idle through town or at the store. I am thinking it may be boiling in the carb but I dont know how to fix it. I have a spacer between carb and intake as well. After a 10 min rest I can dump fuel in carb and im off and running again if i pick up the speed and get the air flowing. But if i slow back down then it does it again. Anyone have any ideas?


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post #2 of 10 Old 06-08-2018, 10:51 PM
TIPPEDITOVER
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Fuel tank vented well?

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post #3 of 10 Old 06-09-2018, 08:42 AM
StoneTower
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If you dump a little fuel in carb. will it fire up if you do not wait 10 minutes? I think if it was vapor lock it still should fire up and burn off the fuel you dump in the carb. It would be a good way to eliminate another problem.

If it does not fire up, check for spark. Maybe you have a ignition module that is going out and when it cools off a bit, it will work again.

I know some people plumb in an electric pusher pump on the frame near the tank to help with vapor lock.
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post #4 of 10 Old 06-09-2018, 12:37 PM Thread Starter
ReedJeepster
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It does fire back up right after so I dont think its spark.

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post #5 of 10 Old 06-09-2018, 12:44 PM Thread Starter
ReedJeepster
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Quote:
Originally Posted by TIPPEDITOVER View Post
Fuel tank vented well?
Nothing has changed on my tank set up since I originally put it together and I never had the issue before. It just started doing it. Could it be that the carb acts up when it gets hot? That is the only thing that I can think of that could change..that and the pump i guess.

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post #6 of 10 Old 06-09-2018, 01:07 PM
Shawn Watson
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Is it an Edelbrock by chance? Those are notorious for vaporizing themselves dry when it gets hot. Although it shouldn't happen if it's getting fuel.


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Last edited by Shawn Watson; 06-09-2018 at 05:46 PM.
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post #7 of 10 Old 06-09-2018, 04:04 PM
KevinCJ7Jeep
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Have you pulled your plugs to check the color, running lean or rich? This has helped me a lot with my jet skis. May not be much help here, but I thought I would bring it up.
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post #8 of 10 Old 06-09-2018, 06:14 PM
Dryseals
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Carb is boiling out, under the hood temperatures are too high. SBC and headers is going to create a lot of heat that needs to go some where. Get an IR temperature gun, measure hood temps while cruising and then measure them again while you are going slow. You might be able to cure it with some header wrap, but to be sure thats whats happening...check hood temps, they will tell you. I would also shoot the carb right after it stalls to see what the temps are on it.
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post #9 of 10 Old 06-09-2018, 08:52 PM Thread Starter
ReedJeepster
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Thanks for the suggestions.

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post #10 of 10 Old 06-11-2018, 07:37 AM
Fourtrail
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What kind of spacer? Aluminum or composite? To isolate from heat you need a composite spacer as an aluminum will transfer all the the motor heat right to the carb. Also go over and check your connections for an air leak between the pump and tank. You may have a weakening fuel pump that can't pull fuel at low rpm/are sucking in just enough air to starve the motor at low rpm.

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