Vapor Lock, how do you cure it? - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 10-23-2000, 01:27 PM
Posts: n/a
Vapor Lock, how do you cure it?

My CJ7's 360 is suffering from vapor lock , what are some ways to cure this?

Could I wrap the fuel lines with some heat resistant material?

Install an electric fuel pump?

Any info is most appreciated.

Sponsored Links
post #2 of (permalink) Old 10-23-2000, 01:46 PM
Join Date: Jan 2000
Location: Green Bay, WI
Posts: 573
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Vapor Lock, how do you cure it?

My guess is that if you have headers on the 360, they're ending up pretty close to the fuel line. Try moving the line farther away from the source of the heat. If it's a ways away from the header, check along the frame where the fuel line runs. If the exhaust comes close, there's the source of your problem. Don't forget to check from the fuel pump to the carb. I believe Summit sells insulating stuff for fuel line, if you need to go that route.


greencj7 is offline  
post #3 of (permalink) Old 10-23-2000, 01:51 PM
Posts: n/a
Re: Vapor Lock, how do you cure it?

I was fighting that with my 350 swap as well. I ended up running new fuel lines inside the frame tubing instead of parallel to the exhaust tubing on the inboard side of the frame and installed a return line. When I first did my swap, wasn't running a return. Without a return, the fuel just sits in the lines waiting to be used. With a return, the warm fuel constantly circulates back to the tank where it mixes with the cool fuel there and gets recycled. I also put a heat shield under the carb. It runs great on hot days now. Much better than before.

Jason '87YJ
"If you didn't build it, it isn't yours . . ."
Sponsored Links
post #4 of (permalink) Old 10-23-2000, 03:05 PM
jeepsternaut's Avatar
Join Date: Jul 2000
Location: North Alabama
Posts: 197
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Vapor Lock, how do you cure it?

Need some help understanding vapor lock to help diagnose problems of my own...I know what vapor lock is, but is your jeep completely cutting out? or just running poorly (hesitating)when you give it gas? also, is vapor lock more of a problem at higher altitudes? I was getting some hesitation out of mine and I suspected vapor lock at one point in time...but have since, I think, curred that problem. With my 360 the line still runs along the right side and over the timing gear cover to the pump.

78 CJ5 w/360
"measure it with a micrometer, mark it with chalk, and cut it with an axe"
jeepsternaut is offline  
post #5 of (permalink) Old 10-23-2000, 05:16 PM
Posts: n/a
Re: Vapor Lock, how do you cure it?

Thanks for the responses! I dont have headers just the stock manifolds.

My Jeep runs great cold but when it warms up runs like crud (hesitation,like only 7 or 8 cylinders are working)

I installed a clear fuel filter when cold is half full of gas but when warm is almost empty (telltale sign of vapor lock I ma told)

I kept the gas line running on the passenger side,then routed it under the engine (along crossmemeber) up to the fuel pump, from the fule pump it goes to a new fuel pressure gauge,fuel filter then to the carb.....I used to run the line up over the right side of the engine to the pump but thought routed it under the engine would keep it cooler.

post #6 of (permalink) Old 10-23-2000, 06:35 PM
InfantryYJ's Avatar
Join Date: Feb 2000
Location: Kernersville, NC
Posts: 1,566
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Vapor Lock, how do you cure it?

I always thought "Vapor Lock" was something you did to a woman.[img]/wwwthreads_images/icons/laugh.gif[/img][img]/wwwthreads_images/icons/laugh.gif[/img][img]/wwwthreads_images/icons/laugh.gif[/img]

I may not like what you say, but I'll defend to the death your right to say it.
Semper Jeep
InfantryYJ is offline  
post #7 of (permalink) Old 10-23-2000, 07:32 PM
Posts: n/a
Re: Vapor Lock, how do you cure it?

I'm sure this isn't the cause of the problem, but you may want to take off the clear fuel filter and use a normal one. The clear filters often have moisture get in around the caps on either end. That's bad.

'82 CJ-7/360/727/D300/M.O.R.E. shackles and lots of ideas!

Have you kissed your JEEP lately?
post #8 of (permalink) Old 10-25-2000, 09:18 AM
Keyboard Implanted
Join Date: Sep 1999
Location: Southeast Iowa
Posts: 6,394
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Vapor Lock, how do you cure it?

[img]/wwwthreads_images/icons/smile.gif[/img] Vapor lock can be caused....or made (1) pinhole leaks in the fuel line to the tank which let the fuel pump suck in air and as the negative pressure acts on the air the bubbles increase in size. At higher altitudes the gas bubbles easier so it is worse. (2) Heat which boils the fuel in the fuel lines. Like on a VW engine there is only about ONE PLACE where you can put the fuel supply line that is cool enough, and that line needs to be steel not black rubber. So protect the lines from heat; use steel whenever possible; and check for pinholes.[img]/wwwthreads_images/icons/crazy.gif[/img]

Quadra-Tracs modified While-U-Wait by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img] Quadra-Trac Team.[img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
CJDave is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome