Default Vapor Lock Issue, Non-vented gas cap help? 

Old 04-19-2010, 11:38 AM   #1
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Is there any issue with using a vented gas cap versus a non-vented? Long story but I had to remove by secondary fuel return line off my fuel filter because the engine would not stay running under acceleration. I now have a single inlet and single outlet fuel filter and enjoy the normal range of acceleration.

I think I know have a vapor lock issue on warmer days. The engine jsut stopped running. Yesterday, I had this issue and I removed the new non-vented gas cap. A fair amount of pressure was released (tank was also full of gas). The vehicle then ran well all the way home.

Any ideas or thoughts about going to a vented cap or modifying the rubber seal on my non-vented, vented?

Thanks for your thoughts, Pat
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Default Re: Vapor Lock Issue, Non-vented gas cap help? 

Old 04-19-2010, 12:20 PM   #2
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Find a vented cap if you can. Trying to mod the cap doesn't work so well.
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Default Re: Vapor Lock Issue, Non-vented gas cap help? 

Old 04-19-2010, 12:27 PM   #3
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Well, first thing I would ask is, was your filter moubnted in the correct orientation? I find that many filters are improperly installed, and will cause problems. The outlet side should be mounted so that the the tubes are stacked one over the other, and not side by side. The top goes to the return line, the bottom to the carb. Mounting the lines upside down or sideways will cause problems. The idea behind the return line is to loop fuel constantly to keep it cooled, and preventing vapor lock. There should be no reason I can think of that your engine shouldn't run just fine with the correct filter and mounting. So I would give it another try being careful to install it correctly. A vented cap may work, and the cost to try is cheap enough, but with fuel sitting in a hot line, you may still find it locking on you.
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Default Re: Vapor Lock Issue, Non-vented gas cap help? 

Old 04-19-2010, 08:29 PM   #4
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Now that's what I like about this place. Useful info just keeps popping up. I just did a carb swap, and after reading this, went out to check on that fuel filter. Uh huh, downside up. Thanks, CW, it's right now.

 

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Default Re: Vapor Lock Issue, Non-vented gas cap help? 

Old 04-21-2010, 12:09 PM   #5
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I second the fuel filter as the cause.
My understanding,also, is that the second tube , oriented to the top, is there to prevent the vapor lock that you are experiencing.
Keep the non-vented cap.
Find out the real reason for the fuel starvation issue. Maybe sunk float or fuel pump with a cracked diaphragm? Both give that same symptom.

 

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