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08-30-2011, 05:38 PM
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CC Member
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Join Date: Jun 2011
Cobra Make, Engine:
Posts: 18
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Not Ranked
Vapor Lock
Hey Everyone,
I've noticed a few times after trying to start the car after CC that it hesitates to start and I think it's vapor lock. Happens especially if I drive the car and stop and try to start it again after 20 min or so aka it hasn't had time to cool down yet. It's a 427R running on 91 octane. Thanks! See some of you in a few weeks at CC...out of town the next two weekends.
Jon
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08-30-2011, 08:33 PM
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CC Member
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Join Date: Feb 2007
Location: Colorado Springs,
CO
Cobra Make, Engine: Backdraft, supercharged Coyote
Posts: 2,445
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Not Ranked
If it spins over easily but won't fire, it's probably vapor lock. If it hesitates to spin over, it's probably an electrical problem - like too small a battery cable.
__________________
.boB "Iron Man"
NASA Rocky Mountain TTU #42
www.RacingtheExocet.com
BDR #1642 - Supercharged Coyote, 6 speed Auto
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08-31-2011, 03:05 AM
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CC Member
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Join Date: May 2008
Location: Brisbane,
QLD
Cobra Make, Engine:
Posts: 2,797
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Not Ranked
What carb/s do you have?
Sounds more like fuel percolation.
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Gary
Gold Certified Holden Technician
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08-31-2011, 04:47 AM
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CC Member
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Join Date: Feb 2002
Location: Dadeville,
AL
Cobra Make, Engine: Sold my EM.
Posts: 2,459
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Not Ranked
We need a little more info to diagnose. Are you running a mechanical or electrical fuel pump?
__________________
Tommy
Cheetah tribute completed 2021 (TommysCars.Weebly.com)
Previously owned EM Cobra
"Never attribute to malice that which is adequately explained by stupidity." - Hanlon's Razor
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08-31-2011, 04:55 AM
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CC Member
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Join Date: Aug 2009
Location: Adelaide,
SA
Cobra Make, Engine: AP 289FIA 'English' spec.
Posts: 13,152
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Not Ranked
Does it help if you turn it over without touching the throttle, and when you hear it just start to catch slightly (might be 10 seconds of cranking), just give it a touch on the accelerator pedal?
Cheers,
Glen
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08-31-2011, 10:14 AM
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CC Member
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Join Date: Jun 2011
Cobra Make, Engine:
Posts: 18
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It's a Holley 750 with mechanical secondaries. I'm not sure about the fuel pump. It's a Superformance Mkiii built in 2006. I'd have to look at the build sheet to find out. In these situations, if I floor the throttle it'll start but blow smoke out the exhaust. Usually isn't a problem unless the car is hot.
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08-31-2011, 10:50 AM
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CC Member
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Join Date: Jan 2011
Location: Rockland County,
NY
Cobra Make, Engine: West Coast Cobra/427
Posts: 853
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Not Ranked
Quote:
Originally Posted by jstillmd
Hey Everyone,
I've noticed a few times after trying to start the car after CC that it hesitates to start and I think it's vapor lock. Happens especially if I drive the car and stop and try to start it again after 20 min or so aka it hasn't had time to cool down yet. It's a 427R running on 91 octane. Thanks! See some of you in a few weeks at CC...out of town the next two weekends.
Jon
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Welcome to my world. As the other responders are saying there is a plethora of thing that can be affecting this. I have a 427 FE Side Oiler with the same problems and this is what I have done in no particular order.Checked the block, heads, header , exit hose and intake manifold temp after 1hr run with an INfra red thermometer for overheating.
Check your coolant water mix should be 50/50 water/coolant plus 1 bottle of water wetter.
changed the starter for a hi-torque starter and covered with a heat shield.
installed a phenolic 1/2" spacer between the carb and the manifold to reduce heat transfer.
Checked the gas level in the carb bowls to ensure is specs.make sure that you are not dripping gas into the plenum vua looking down the carb after a run.
checked timing.
heat shielded the gas line from gas pump(mechanical) to carb and incoming hose from tank to gas pump immediately underneath the headers)
Changed the gas filter element.
Theoretically the heat from the engine is overboiling the gas leaving us with slim to no gas on the carbs making it difficult to start or maintain nice idle in heavy traffic. That is vapor lock. I thought about installinf a cool can, however, space availability and net positive effect did not warrant the expense. Plus you would have to carry a cooler with dry ice in the trunk , not too convenient.
I sincerely hope that one of these things work, the starter option I knew I had to change the starter for I rather have the hi-torque type thats just me.
Happy motoring.
Basque1
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08-31-2011, 01:31 PM
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Senior Club Cobra Member
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Join Date: Jul 2000
Location: Las Vegas,
NV
Cobra Make, Engine: ERA 427 SO
Posts: 1,126
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Not Ranked
That's a slightly rich or flooded condition from heat percolation, not vapor lock...just hold the pedal to the floor during hot starts. Aggravating but managable.
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Ken
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08-31-2011, 02:08 PM
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CC Member
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Join Date: Jul 2009
Location: Frisco,
TX
Cobra Make, Engine: BackDraft, Keith Craft 408; 1967 GT500CR
Posts: 355
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Not Ranked
Big believer in a phenolic spacer for these issues--with our government corn gas it's going to become a necessity. A serendipitious effect is improved midrange performance.
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CONSTANT CHANGE IS HERE TO STAY.
Last edited by snakebittexan; 08-31-2011 at 02:11 PM..
Reason: sp.
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08-31-2011, 02:26 PM
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CC Member
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Join Date: Jun 2011
Cobra Make, Engine:
Posts: 18
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Yeah if I hold the pedal to the floor during hot starts it will usually start...it sounds ugly and I just want to make sure I'm not hurting the engine. So this is ok to do?
I've also read about phenolic spacers. A lot of people seem to like them so I'm going to consider that as well.
Thanks for all the suggestions!
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08-31-2011, 02:45 PM
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CC Member
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Join Date: Nov 1999
Location: Las Vegas,
NV
Cobra Make, Engine: Classic Roadster; 351W
Posts: 743
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Not Ranked
Hard to avoid percolation in Las Vegas. Phenolic spacers, heat shiedling of fuel lines help to a degree but it is hard to completely avoid it in summer time. Pedal on the floor while starting usually gets it fired
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02-21-2013, 03:40 AM
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CC Member
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Join Date: Feb 2013
Cobra Make, Engine:
Posts: 1
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What can I do to stop vapor lock in my riding mower?
Poulan Pro 18.5 horse mower. two years old. Gets hot and shuts down. All filters replaced, new plug and oil change. Had $300 worth of work done and still not running right. I was told it could be vapor lock.
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02-21-2013, 04:33 AM
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CC Member
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Join Date: Jul 2010
Location: McMurray,
PA
Cobra Make, Engine: Superformance #522
Posts: 528
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Not Ranked
Using ethanol free gas or blending in race fuel helps.....higher vapor point.
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02-21-2013, 05:24 AM
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CC Member
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Join Date: Feb 2002
Location: Dadeville,
AL
Cobra Make, Engine: Sold my EM.
Posts: 2,459
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Quote:
Originally Posted by eddyjuan554
Poulan Pro 18.5 horse mower. two years old. Gets hot and shuts down. All filters replaced, new plug and oil change. Had $300 worth of work done and still not running right. I was told it could be vapor lock.
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Apparently, that damn Shelby would put his name on anything if the price was right.
__________________
Tommy
Cheetah tribute completed 2021 (TommysCars.Weebly.com)
Previously owned EM Cobra
"Never attribute to malice that which is adequately explained by stupidity." - Hanlon's Razor
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02-21-2013, 09:07 AM
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CC Member
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Join Date: Jan 2008
Location: Celebration,
FL
Cobra Make, Engine: Superformance #2144 with a Roush 342R (sold June 2018, but still lurking on Club Cobra)
Posts: 128
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Not Ranked
I experienced the same sort of situation with my Superformance. I experimented with different "fixes" but the most helpful was installing a wooden spacer under the carb. I tried a phenolic 3/4" spacer and it helped, but at the urging of a friend, I switched to a 3/4" wooden spacer and that all but cured it. I don't have a supplier name, or source, for the wooden spacer-----a friend had it and gave it to me. It appears to be a laminated wood, similar to high-grade marine plywood. It is definitely not a home built product.
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02-21-2013, 10:26 AM
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CC Member
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Join Date: Dec 2004
Location: Kansas City,
KS
Cobra Make, Engine: jbl
Posts: 2,291
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Not Ranked
Quote:
Originally Posted by eddyjuan554
Poulan Pro 18.5 horse mower. two years old. Gets hot and shuts down. All filters replaced, new plug and oil change. Had $300 worth of work done and still not running right. I was told it could be vapor lock.
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did they check your valve clearance?
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02-21-2013, 06:33 PM
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CC Member
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Join Date: May 2001
Location: California,
Ca
Cobra Make, Engine: NAF 289 Slabside Early Comp Car with 289 Webers and all the goodies. Cancelling the efforts of several Priuses
Posts: 6,592
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Not Ranked
eddyjuan554
Get some goats........no gas and they will keep it short.
__________________
Rick
As you slide down the Banister of Life, may the splinters never be pointing the wrong way
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02-21-2013, 07:44 PM
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CC Member
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Join Date: Jan 2009
Location: Jonesboro,
AR
Cobra Make, Engine: Backdraft 874 solid red Roush 427 small block 515 hp
Posts: 572
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Not Ranked
45-50 years ago, drag racers in Arkansas used wooden clothes pins to work a heat sinks and to keep gas line away from heat sources.
They also iced down intake manifold to prevent vapor lock. Who knows if it worked?
__________________
There were no atheists in the foxholes.
Last edited by rpatton3; 02-21-2013 at 07:45 PM..
Reason: Typo
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02-21-2013, 08:14 PM
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CC Member
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Join Date: Feb 2009
Location: Greer,
SC
Cobra Make, Engine: ERA #778 427SC Keith Craft FE 428 stroker
Posts: 243
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Not Ranked
Clothes pins! Yeah, I remember! One time I must have put 20 of them on the fuel line going to a Carter AFB 4-barrel that was driving me crazy because it wouldn't start when hot! Boy, haven't thought of that in years. You should have see it - clothes pins clamped along the entire length of the fuel line. Can't remember if it fixed the problem or not...
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02-21-2013, 11:48 PM
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CC Member
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Join Date: Sep 2009
Location: Camarillo,
CA
Cobra Make, Engine: SPF #2608, Roush 427SR T-W
Posts: 911
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Not Ranked
If you can wait until June you can get some summer gasoline which is less likely to cause vapor lock. I expect your problem is more likely due to ethanol than vapor lock. Does the manufacturer say anything about using gasoline with ethanol?
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