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Unread 06-29-2006, 11:51 AM   #1
lookin4mud
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How do I stop vapor lock??

So my jeep decides to start vapor locking this summer. What can i do to cure it? I was told that it was a defective gas cap, so i switched that but it didn't help at all. It's an 89 with 4.2, stock carb, nutter bypass.

I narrowed the problem down to vapor lock because it only does it on my way home from work when it's hotter outside. in the morning and on short trips it runs fine. When it shuts off, i can get it started back up, but i have to wait a minute or two.

thanks for the help.

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Unread 06-29-2006, 12:11 PM   #2
dadstoy
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I put wooden clothes pins on my metal fuel line once for a quick fix. Not sure of any permanent fixes.
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Unread 06-29-2006, 12:42 PM   #3
offroadyjguy
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Is your tank still vented threw the canister? On our jeeps the tank can not vent threw cap. Make sure tank is vented
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Unread 06-29-2006, 04:31 PM   #4
laybackman
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Quote:
Originally Posted by lookin4mud
So my jeep decides to start vapor locking this summer. What can i do to cure it? I was told that it was a defective gas cap, so i switched that but it didn't help at all. It's an 89 with 4.2, stock carb, nutter bypass.

I narrowed the problem down to vapor lock because it only does it on my way home from work when it's hotter outside. in the morning and on short trips it runs fine. When it shuts off, i can get it started back up, but i have to wait a minute or two.

thanks for the help.
If your tank is not vented it would not run well in any weather. As gas comes out atmosphere must go in. A simple restart would not fix the problem either. Classic vapor lock is heat related and the only fix being isolate the fuel from any excess heat source (or cool off the fuel using a cool can). Try wrapping your fuel lines in aluminum foil. I think you may have another issue here. Maybe a bad cat converter?
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Unread 06-30-2006, 11:38 AM   #5
lookin4mud
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Quote:
Originally Posted by laybackman
If your tank is not vented it would not run well in any weather. As gas comes out atmosphere must go in. A simple restart would not fix the problem either. Classic vapor lock is heat related and the only fix being isolate the fuel from any excess heat source (or cool off the fuel using a cool can). Try wrapping your fuel lines in aluminum foil. I think you may have another issue here. Maybe a bad cat converter?
wouldn't a jeep run fine even without a cat converter? unless it was clogged i guess, but the exhaust seems to be coming out fine. what's a cool can? could i get one cheap? right now most of the fuel lines are covered with plastic wire conduit.

dadstoy:
has does the wooden clothes pin thing work?
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Unread 06-30-2006, 12:23 PM   #6
dadstoy
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It worked for me. I had the problem several times before I put them on. I asked several guys from work and they diagnosed vapor lock and offered that quick solution. They were on the truck for 2 years and never had any more vapor lock problems. When I sold the truck to my uncle, he asked what they were for and laughed, but they did the job for me.
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Unread 06-30-2006, 01:33 PM   #7
JFM626
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There are different ways to combat vapour lock, ranging from cheap and easy to expensive and intricate.
Cheap and easy:- head for the kitchen, get some tinfoil and wrap it loosely around the fuel lines that are near the engine. Reflects heat.
Not so cheap and easy :- remove the line from the engine mounted fuel pump that goes to the carburetor. get a old coffee can from under the sink, mount it somewhere convenient under the hood. Run a new steel line from the fuel pump to the coffee can and coil it several times to fit inside the coffee can. Connect the line to the carburetor. Fill the coffee can with ice and water. Now you have a cool can. Carry lots of ice
Expensive and intricate:- Buy an electric fuel pump, mount it near the tank, run a new line to the carburetor, with a T fitting near the carburetor, run two lines from the T. One to the carburetor and one back to the fuel tank. This line has to be a restricted flow line. 1/8th id is fine.
Most of the time, cheap and easy does the trick. Clothes pins sound interesting, haven't heard that one before; but hey it's cheap and easy.
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Unread 06-30-2006, 07:56 PM   #8
laybackman
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Quote:
Originally Posted by lookin4mud
wouldn't a jeep run fine even without a cat converter? unless it was clogged i guess, but the exhaust seems to be coming out fine. what's a cool can? could i get one cheap? right now most of the fuel lines are covered with plastic wire conduit.

dadstoy:
has does the wooden clothes pin thing work?
The clothes pins probably work as a heat sink. I would wrap your fuel lines with aluminum tin foil and insulate them.
Maybe you have made a change in your engine bay that has caused this problem, since this problem is new this Summer. How about fuel line changes of any sort? Did you remove/change your air cleaner? Did you make any changes in your carbeurator? How about your fan shroud did you remove it?
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Unread 07-03-2006, 11:40 AM   #9
lookin4mud
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Quote:
Originally Posted by laybackman
The clothes pins probably work as a heat sink. I would wrap your fuel lines with aluminum tin foil and insulate them.
Maybe you have made a change in your engine bay that has caused this problem, since this problem is new this Summer. How about fuel line changes of any sort? Did you remove/change your air cleaner? Did you make any changes in your carbeurator? How about your fan shroud did you remove it?
the only thing that has been changed since last summer is the fuel filter (new, stock replacement). I also put in a new thermostat, but according to the gauge on the dash the jeep's running cooler. i'm going to try the alum. foil thing. if that doen't work, i'll try rerouting my fuel lines.
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Unread 07-03-2006, 04:14 PM   #10
Richmond88yj
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I'm fighting the same problem, 4.2 post nutter, holley replacement instead of carter....

I vented my canister and am going to try to "foil on the lines tomorrow.

The 4.2 has the mechanical pump routing the lines right up over the motor, and the soft lines (post holley) are right above the exhaust manifold.

I'll post tomorrow on the tinfoil and canister vent solution after my 30 mile run to work and back (in the heat)
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Unread 07-03-2006, 08:58 PM   #11
laybackman
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Another consideration would be that you are "post Nutter". Maybe you need to tweak your timing a bit also.
Just remember to change only one thing at a time. That way you know if what you did last fixed the problem or made it worse.
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Unread 07-04-2006, 08:40 AM   #12
rutacon05
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i'm a newbie to this site, just happend to stumble across this question. and this might be off the wall but the little things sometimes trip you up. dad had an 84 3/4 sub. w/350 thing sat alot, lot of rust, suffered from vapor lock right off lot used. installed fuel pump dif. location, rerouted lines. i crawled under one day with him, not being the mechanical wizzard, suggested we dissconnect line, blow air through it, there was a pin hole in one of the lines, i'm guess return line?, new line. fixed! i did the dirty work, i'm little haha!
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Unread 07-04-2006, 08:55 AM   #13
JFM626
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Way to jump in there Joe. Welcome to the Form. And you're right, could well be something like that.
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