vapor lock
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Junior User
Joined: Jun 2006
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From: SW MN
vapor lock
My 1969 f250 has a 390 engine with a 2-barrel carb. If I put a 4-barrel carb. on, will it help with the problem of vapor locking? What are some of the best ways of solving this problem?
Thanks
Thanks
Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
It depends on what you are calling Vapor lock. Usually what folks call vapor lock is any
disruption of fuel being delivered to the carburetor.
There is no actual mechanical way that fuel vapors can stop liquid fuel being pumped to the carburetor if the tank has fuel, the draw tube & sock are good, there are no cracks or holes in the fuel lines, the filter is clear and the pump works right.
If you have a hot start problem, it may be caused by the carb boiling fuel into the intake when the hot engine is shut down causing the engine not to fire up & run, until the carb refills . . . . .
But if you go from a 2V carb to a 4V carb you would be increasing potential problems because there is 2X the quan of fuel present to heat & spill into the intake. Are you running the correct heat shield insulator base palte under your 2V carb Now?
FBp
disruption of fuel being delivered to the carburetor.
There is no actual mechanical way that fuel vapors can stop liquid fuel being pumped to the carburetor if the tank has fuel, the draw tube & sock are good, there are no cracks or holes in the fuel lines, the filter is clear and the pump works right.
If you have a hot start problem, it may be caused by the carb boiling fuel into the intake when the hot engine is shut down causing the engine not to fire up & run, until the carb refills . . . . .
But if you go from a 2V carb to a 4V carb you would be increasing potential problems because there is 2X the quan of fuel present to heat & spill into the intake. Are you running the correct heat shield insulator base palte under your 2V carb Now?
FBp
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Junior User
Joined: Jun 2006
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From: SW MN
I never put a different base plate on, but that doesn't mean that the person who owned it before me put a different one on that isn't the correct one.
I was wondering if I could put a little electric fuel pump somewhere in-line before the fuel pump that I have now. Then I would mount a switch in the cab for it and every time it vapor locks, I could flip the switch and it would pump new fuel into the carburetor. Would something like that work?
I really want to solve this problem when it doesn't start when the engine is hot.
Thanks
I was wondering if I could put a little electric fuel pump somewhere in-line before the fuel pump that I have now. Then I would mount a switch in the cab for it and every time it vapor locks, I could flip the switch and it would pump new fuel into the carburetor. Would something like that work?
I really want to solve this problem when it doesn't start when the engine is hot.
Thanks
Fleet Mechanic
Joined: Jul 2004
Posts: 1,988
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From: Travelers Rest SC
I always thought vapor lock was fuel boiling in the fuel line, and thus the pump didn't have any liquid to work with. I've seen people try to insulate the fuel line. Whatever the cause, I use to cure it years ago with an electric pump back closer to the tank, away from the hot engine.
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Junior User
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From: SW MN
There is some kind of a metal spacer underneath of the carburetor right now. It looks like it serves no purpose but to raise the carburetor up higher. Is that the phenolic spacer or does the phenolic spacer goes on top of that piece?
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Logistics Pro
Joined: Jun 2003
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Originally Posted by oscar_007
There is some kind of a metal spacer underneath of the carburetor right now. It looks like it serves no purpose but to raise the carburetor up higher. Is that the phenolic spacer or does the phenolic spacer goes on top of that piece?
What I believe you're experiencing is fuel boiling in the float bowl.
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4wd Low
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While vapor lock is rare, it does occur. But if you just have a "hot start" problem, perhaps this will help:
http://www.thecarburetorshop.com/Tro...m#Hardstarthot
Jon.
http://www.thecarburetorshop.com/Tro...m#Hardstarthot
Jon.
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