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Topic: Vapor Lock?

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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Vapor Lock? (1/15)
 7/17/08 11:29pm
KDADDY79
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Dutchess County, NY - USA

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White '79 Corvette. It's a driver.


Joined: 8/27/2007
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Today it was about 90 degrees with a good dose of humidity.

I drove my Corvette around town for about 10 minutes. It ran well and the temp gauge never went above 220 degrees.
When I got back home I parked it for about 10 minutes with the hood up. ( I always open the hood to let out excess heat after driving it.)
 
My son's friend needed a ride home, so I took him in the Corvette.
While on that short ride I never went over 35 MPH as we were on residential streets. Just before getting the kid home I let off the gas and the motor stalled.
I opened the hood and smelled a good amount of gasoline fumes. No gasoline or other fluids were dripping from the motor on to the ground.
I let it sit with the hood open for about 10 minutes. No more gas fumes.
Then it started back up just fine and ran good after that. The temp gauge remained below 220 degrees the whole time.
 
What does this sound like? Was it "Vapor Lock"? 
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Vapor Lock? (2/15)
 7/17/08 11:38pm
wdwrkr4
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Loveland, CO - USA

Vette(s):
Red 1980 L48 TH350 Automatic, Edelbrock Performer Intake, Hooker Headers Sidepipes. Doeskin Cloth Interior, Collector's Edition Lifting Rear Hatch.


Joined: 9/30/2007
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I've been having a bad go of it this week as well. Mine cuts out at heavy throttle. I live at 5000 feet above sea level and it has been 100 degrees. Doesn't do this at all in milder temperatures.

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Vapor Lock? (3/15)
 7/17/08 11:47pm
KDADDY79
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Dutchess County, NY - USA

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White '79 Corvette. It's a driver.


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Posts: 2484

Could it be that the gasoline actually starts to boil before it gets to the carb? I know the motor was throwing off some serious heat. 
Is the air temp. under the hood so hot that the car breaths in hotter than normal air & this stall was caused by it?
 
I'm just diggin' for some ideas.  
Vapor Lock? (4/15)
 7/18/08 12:46am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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Vapor lock is indeed caused by fuel boiling in the line...it creates a vapor as the liquid fuel boils in the fuel line, which doesn't allow any more liquid fuel to pass.
Some folks scoff at the old "wooden clothes pin on the fuel line" thing, but it does work. The wood basically soaks up the heat from the line, keeping the line from getting hot enough to cause the vapor lock. I've seen guys with Mid-Years have 10-15 clothes-pins on their fuel lines when driving on a road trip...


I had a 69 Pontiac Bonneville/428 a long time ago. A couple of friends and I decided to take a road trip down the Pasadena, Tx, to go to the new Gilly's club.(This was right after the Urpin Cowboy movie came out )
On the way home, the old Pont started the dreaded vapor lock. We were all tired...and maybe just a wee bit sloshed, and not really in the mood for car troubles.
Not having a stash of clothes-pins, I wound up soaking some shop towels in...er..well, the only liquid we had at the time....beer! I wrapped the rags around the metal fuel line, and we kept on trucking. Made it back home in just enough time to go to werk...
The beer-soaked rags cooled the metal line enough to kill the vapor lock...Adams' Apple2008-07-17 21:53:08

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Joel Adams
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Vapor Lock? (5/15)
 7/18/08 1:10am
DaveMLifetime Member
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Flanders, NJ - USA

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Hey Kevin, do you have headers on your car? If you do make sure the fuel line isn't too close to the header.
PM sent,
Dave


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Vapor Lock? (6/15)
 7/18/08 5:14am
Jeffm
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Sebago Lake, ME - USA

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Should it really be running up near 220?? Since I did a new rad and finally got the air pocket out (drilled 1/8" hole in  thermostat which I learned here) mine never gets near that 200 mark. Out yesterday for an hour or so in close to 90 degree weather.
Vapor Lock? (7/15)
 7/18/08 7:46am
80VetteMan
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I will have to remember that one Joel..   Make sure i buy a beer for the vette!
Vapor Lock? (8/15)
 7/18/08 8:01am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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Vapor lock is not totally caused by heat alone...heat is just the major factor.
The volatility of the fuel has a role in the phenomenon, also. I think Ken has posted a really good explanation of it in another thread somewhere.

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Joel Adams
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Vapor Lock? (9/15)
 7/18/08 8:58am
wdwrkr4
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Loveland, CO - USA

Vette(s):
Red 1980 L48 TH350 Automatic, Edelbrock Performer Intake, Hooker Headers Sidepipes. Doeskin Cloth Interior, Collector's Edition Lifting Rear Hatch.


Joined: 9/30/2007
Posts: 28

Adam, would you put the clothes pins on the fuel line between the tank and the pump, or between the pump and the carb, or both?
  Thanks,
     Matt


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Vapor Lock? (10/15)
 7/18/08 9:01am
wdwrkr4
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Loveland, CO - USA

Vette(s):
Red 1980 L48 TH350 Automatic, Edelbrock Performer Intake, Hooker Headers Sidepipes. Doeskin Cloth Interior, Collector's Edition Lifting Rear Hatch.


Joined: 9/30/2007
Posts: 28

Sorry Joel, your name is not Adam.
  Matt


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Vapor Lock? (11/15)
 7/18/08 9:27am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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[QUOTE=wdwrkr4] Adam, would you put the clothes pins on the fuel line between the tank and the pump, or between the pump and the carb, or both?
Thanks,

     Matt
[/QUOTE]

You want to put them on the metal line from the pump to the carb...not always the easiest thing to do, depending on how much other crap is covering the line. 5-6 will usually work, but the more you have on there the more heat they will absorb from the line. It looks stoopid as heck, but...it'll get ya down the road! I know the guys that use this trick will put them on before taking of on a trip...."preventative maintenance!!"


oh....I get called waaaay worse things than "Adam", believe me!

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Vapor Lock? (12/15)
 7/18/08 11:35am
KDADDY79
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Dutchess County, NY - USA

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White '79 Corvette. It's a driver.


Joined: 8/27/2007
Posts: 2484

Folks,
Thanks for the input!
I think (hope?) it was a one time thing caused by some pretty hot (for these parts) weather.
I'm going to try the clothes pin thing today. We're gettin' scorched again!
 
The 220 degree mark is kind of a standard I've learned with this car. It's never gone above 220 and usually stays well below it with minimal air flow & RPMs.
 
 
Vapor Lock? (13/15)
 7/18/08 9:40pm
KDADDY79
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Dutchess County, NY - USA

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White '79 Corvette. It's a driver.


Joined: 8/27/2007
Posts: 2484

Well, I took it for a ride in the late afternoon. The temp. had dropped down to the high 80s. I tried the clothes pins trick and it worked very well in around town driving.
A couple of shut offs & restarts later it still seemed just fine.
 
So, off my son and I went for a nice ride.
About 45 minutes in to driving on country roads the motor backfired pretty loud. ( I swear it came from only the right side of the dual exhaust. That's the way it sounded to me.) I put it in neutral and revved it. It kept running.
We came to a traffic light & stalled. Started right back up again & I pulled over & shut it off.
I opened the hood and smelled alot of gasoline fumes. No other smells like when a motor overheats & no fluids dripping on to the ground.
I left the hood open for a half hour. Took off the air cleaner, too. I was hoping everything would cool down enough for a restart.
 
Tried to restart it. It ALMOST started but not quite. I pushed down all the way on the gas pedal and cranked it again. It went KABOOOOOM!!! It seemed like this explosion went straight up from the carb.
 
So, on to the flatbed it went & it's sitting indoors at a friend's shop.
We'll give it a look tomorrow.
Timing?
Bad Distributor or just the Ignition Coil?
Should I have used a real wooden clothes pin instead of those pink plastic ones? (Just jokin' LOL)
 
Any input is welcome & thanks in advance.
 
 
 
KDADDY792008-07-19 09:36:51
Vapor Lock? (14/15)
 7/19/08 2:23pm
KDADDY79
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Dutchess County, NY - USA

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White '79 Corvette. It's a driver.


Joined: 8/27/2007
Posts: 2484

Now bare with me. I'm fishin' for some ideas here. Stern%20Smile
 
I don't have headers. So no obvious culprit there.
 
In reference to the big KABOOOOOM when trying to restart it, did the dist. fail to give enough or any spark. Then too much gas ignited like the 4th. of July when it did finally provide spark?
 
I'm at a stand still until Monday. I appreciate any input.
Thanks!
 
P.S. The underside of the cap was clean. No buildup or anything.
       The rotor did have some up & down play. About a 16th. of an inch I'd
       guess.
KDADDY792008-07-19 11:31:39
Vapor Lock? (15/15)
 7/20/08 10:20pm
KDADDY79
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Dutchess County, NY - USA

Vette(s):
White '79 Corvette. It's a driver.


Joined: 8/27/2007
Posts: 2484

Any ideas?Confused
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