What causes vapor locking and how to fix it
07-15-2007, 08:39 PM
#1
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What causes vapor locking and how to fix it Ok guys I am helping a buddy with an 81 Jeep cj-5. 304 v8, basically stock. When the jeep gets above 10k feet of elevation it begins to sputter and die. Does anyone know what causes this and how I could remedy the problem? A shadetree mechanic told us to put a holley blue just in front of the fuel tank and use it as a pusher pump to the mech. pump. Anyone have any advice?
07-15-2007, 09:58 PM
#2
It's more of a jetting issue than a vapor lock. Vapor lock is from the fuel getting too hot and flashing to a vapor vs a liquid. High altitude causes a abnormally rich condition (less O2).
Jetting the Jeep down or adding an oxygenated fuel (VP109) will fix the problem. ATVs have the same issue.
Good luck!
Jetting the Jeep down or adding an oxygenated fuel (VP109) will fix the problem. ATVs have the same issue.
Good luck!
07-15-2007, 11:09 PM
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Originally Posted by TXCAMSS
It's more of a jetting issue than a vapor lock. Vapor lock is from the fuel getting too hot and flashing to a vapor vs a liquid. High altitude causes a abnormally rich condition (less O2).
Jetting the Jeep down or adding an oxygenated fuel (VP109) will fix the problem. ATVs have the same issue.
Good luck!
Jetting the Jeep down or adding an oxygenated fuel (VP109) will fix the problem. ATVs have the same issue.
Good luck!
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07-16-2007, 09:10 AM
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Originally Posted by MrDude_1
TXCAMSS answered it.. but if he changes elevation that much on a regular basis, it might be in his best interest to swap to EFI..
Exactly. Cars built and delivered to Denver have a different programming due to the thin air. Same theory here, only you are going 2x higher than that.
07-16-2007, 03:20 PM
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Thanks TXCAMSS. The jeep still has a carb bc it is only taken to colorado to the mountain trails 1x per year. This all makes sense now bc now matter how hard you run it at 3000 feet of elevation it never does this but when in the mountains it shuts down above the treeline ~10k feet and the trails in the Rockies regularly exceed 13500. So, let me get this straight........jet the jeep down really lean locally and when she gets to the mountains it should do much better? Is VP109 economically feasible per gallon? Thanks to all the guys above who had input and if you can think of anything else it would be appreciated.
07-16-2007, 03:37 PM
#10
The VP109 is a bit expensive for that use ($6.00-$7.00/gallon I think).
Another option is to go with an easily adjustable carb. The old Quadrajunk had front metering valves so you could raise or lower the needles to control AFR, but I would go with a separate carb all together that's jetted properly for the higher altitude. A carb swap is quick,easy and less technical IMO for the purpose the Jeep serves.
Another option is to go with an easily adjustable carb. The old Quadrajunk had front metering valves so you could raise or lower the needles to control AFR, but I would go with a separate carb all together that's jetted properly for the higher altitude. A carb swap is quick,easy and less technical IMO for the purpose the Jeep serves.
07-16-2007, 03:43 PM
#11
Another option is an alternative fuel tank for the higher altitude, you could run the oxygenated fuel only when needed or run an oxygenated additive like Coxoc. The Coxoc is about $65.00-$75.00 and makes 5 Gallons. It's not cheap either, but if it's for temporary use, it's cheaper than an extra carb. Just a thought.
07-16-2007, 03:59 PM
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Originally Posted by TXCAMSS
Another option is an alternative fuel tank for the higher altitude, you could run the oxygenated fuel only when needed or run an oxygenated additive like Coxoc. The Coxoc is about $65.00-$75.00 and makes 5 Gallons. It's not cheap either, but if it's for temporary use, it's cheaper than an extra carb. Just a thought.
One more thing......the jeep doesnt really seem to start flooding out, just sputtering and losing power with no black smoke.
07-16-2007, 04:56 PM
#13
It's not entirely a flooding issue as much as an inefficiency. 1 Gallon of Coxoc mixes to make 5 Gallons of fuel and use 93 octane to help the issue you are having. I have bought it off of Ebay for testing purposes. I never got to use when the air quality and track were optimum. It makes additional HP when tuned for it. I actually still have a gallon of it that I was saving for the "perfect day" that never came.lol. It has an infinite shelf life when sealed.
I went on an Elk hunting trip in Colorado about 8 years ago and of the 7 ATVs we had, the Suzuki Quad was the only ATV that would run and idle stable at that altitude, but it was borrowed from guy that lived in higher altitude also so it was jetted for the area.
Here's a link that explains what you are experiencing.
http://www.highaltitudelife.com/autocare.htm
I went on an Elk hunting trip in Colorado about 8 years ago and of the 7 ATVs we had, the Suzuki Quad was the only ATV that would run and idle stable at that altitude, but it was borrowed from guy that lived in higher altitude also so it was jetted for the area.
Here's a link that explains what you are experiencing.
http://www.highaltitudelife.com/autocare.htm
