Vapor Lock!!!!! - Chevy Nova Forum
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Old 7th-July-2010, 04:18 PM   #1
wcjames01
 
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Unhappy Vapor Lock!!!!!

I have a VAPOR LOCK in the gas line from the fuel pump to the carb. I have a 3/8' gas line hose there (rubber). I did have a metal gas line that got extremely hot, which is why I replaced it. I have wrapped the line in HVAC 260degree high aluminum tape, then wrapped that in a split garden hose and again with the HVAC tape. I have a standard plastic fuel filter at the top going into the carb. This is so that I can tell if it is vaporizing or not. Is there a hose that can be exposed to very, very high heat. My guess is that it probably gets to about 260+ under the hood. I have been left stranded to wait on it to cool off about 6 times and I have only had it for almost 2 weeks. I have less than 3-4 days to get this car running right and highway worthy. This is my daily driver!! If you know of a solution please let me know.
Thank you for your help,
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Old 7th-July-2010, 04:52 PM   #2
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wcjames, I was having similar issues, and wondering about vapor lock too. I ended up replacing the fuel pump (same pump design, the first one was from Summit, the second one from NAPA) and the car hasn't died since, although it has yet to be truly driven in rush hour traffic. Two questions for you are, how close is the fuel line to the exhaust, and how close is it to the radiator hose?
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Old 7th-July-2010, 04:57 PM   #3
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I agree. The pump and shaft needs to be inspected. I had a brasstipped pushrod for a roller cam that over time the tip wore away causing low flow and pressure. The diaphragm in the pump may be going out.

It sounds like you have it protected well from heat.
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Old 7th-July-2010, 05:31 PM   #4
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Do some searching on the site and you will find almost everything that has to do with the "Vapor Lock" myth that most inexpierienced mechanics jump to if there having problems with the fuel system. Vapor lock is rare at best and since you are constantly moving fuel at pressure and your engine bay may get at tops around 200 degrees at idle in 100 degreee weather your motor actually expieriencing vapor lock is probably not the cause of your problems. Check your fuel pressure, carb set-up and timing, as these are the most common problems with poorly running engines. Start reading and you will most likely find the problem is something easy that you have overlooked or not taken into consideration.

Look at this post.......it might help.


http://www.stevesnovasite.com/forums...d.php?t=154570
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Old 7th-July-2010, 05:35 PM   #5
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vapor lock

I too had problems with the car stalling after bringing the nova home. When I questioned the original owner about a clothespin clipped to the factory fuel line above the fuel pump, he proclaimed the the clothespin dissipated heat to prevent vapor lock!!! The older gentlemen seemed quite trustworthy, however after the car stalled a couple times, I replaced the fuel pump with new one and haven't had a problem since. The pumps are relatively inexpensive. (still have the clothespin for future bouts of vaporlock!!!)
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Old 7th-July-2010, 09:32 PM   #6
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I have to agree with the fuel pump diagnosis. Before I bought my 62 post car years ago the kid who owned it had trouble with it stalling. When it would happen there seamed to be very little fuel getting to the carb. We would blow backwards through the line to the fuel tank and it would start.

We thought that the pick up in the tank or line was plugging. After he sold me the car I went for a drive with a new pump and tools along for the ride. When the car stopped I changed the pump along side of the road and it never stalled again.

If you have not changed the pump do so and let us know if it helps. If you have a newer pump check the fuel pressure to be sure it is up to normal.

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Old 9th-July-2010, 10:15 AM   #7
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Here is the fuel system trouble shooting chart from my 62 shop manual.
I am not sure if it will help but check it out. Hope you can read it ok.

Even if the fuel pump is newer you could still have a problem with a sticking discharge check valve or debris out of the tank causing it to stick open.

I had a pump go bad a few years ago. The car died and would not start at all. I took the old pump apart and found that the one check valve (don't remeber which one) was popped out of its seat. I was not sure what caused it. I also found a chunk of rust that look to big to have made through the fuel line but it must have been ahead of the pump some were. New pump and all has been good since then.

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Last edited by EARLYIIS; 9th-July-2010 at 10:38 AM.
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Old 11th-July-2010, 08:52 AM   #8
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The pump

Thank you for the feed back everyone. I had a new pump on it before I thought it went bad or had some rust in it. I replaced it on the side of the road. The filter into the carb filled up and i drove it for about 6 miles and it did it once again. I have all of the vacume hoses hooked up and the tank is sealed good. I do not know about around the gas cap. It still gets plenty of fuel if I let it sit for about 30 min. The gas lines never get too hot to touch now that they are wrapped.
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Old 11th-July-2010, 08:55 AM   #9
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Vapor lock or not?

I have sealed the tank locking ring and drove for a little while. I cut the car off to go into the store and when I got back in the car to crank it and leave, it didn't want to start. I popped the hood and there was a little gas in the filter but it wasn't full. All of my gas lines are tight so I know there is no air getting in there. How can I assure the correct air mixture for the carb. I have adjusted it all the way in and then back out 1 complete turn. Oh Yea!! My valve cover has two holes: 1 for the PCV Valve and 1 for the gas vapors to go back into the engine. Does it matter which PCV hose goes to the carb? The upper is to the front and the lower is to the fire wall side.. Sorry to bother you so much, I'm just trying to get it to daily drive. I can deal with the shifting problem.
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Old 11th-July-2010, 09:13 AM   #10
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Hey Wcjames01,

Does the car stall while driving or when you are coming to a stop or is it hard to restart restart it when it is hot.

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Old 11th-July-2010, 09:37 AM   #11
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It idols a little funny when comming to a complete stop. It is almost like the gas pedal mechanisim is sticking. But it doesn't want to re start after sitting for a few minutes. That is when the top filter isn't full of gas.
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Old 11th-July-2010, 09:47 AM   #12
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Quote:
Originally Posted by wcjames01 View Post
It idols a little funny when comming to a complete stop. It is almost like the gas pedal mechanisim is sticking. But it doesn't want to re start after sitting for a few minutes. That is when the top filter isn't full of gas.
Read through the tread I have attached here. I often have to keep the throttle part way open to get it to start when it has set of a short time hot. This tread discuses this problem. Also check out the link in this tread to the Carborator shop, real good info on how your carb works there.

http://www.stevesnovasite.com/forums...d.php?t=154086

PS funny idle could be a lot of things including a vacuum leak.

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Old 12th-July-2010, 03:21 AM   #13
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You mention the filler cap is sealed. This could be your problem or has your tank got a breather line. I had a problem were my engine would starve for fuel when I floored it on a long straight road. I looked into it and found the breather line from the gas tank running up to the front of the car on the drivers side had a block in it. I disconnected both ends and blew air down it with my compressor and it eventually cleared. That solved the fuel starvation problem.
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Old 12th-July-2010, 08:18 AM   #14
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The filler Cap!!

If the cap isn't sealed it would not be getting the correct pressure. My tank also only has the filling spout and the line out to the pump. That's wht I say this thing has me stumpped. It has to be something very minute. I'm going to put in some SeaFoam today to see if it may be a internal thing. Does it matter which of the two hoses from the PCV valve go to which vacume. My bottom hose goes towards the fire wall and the top hose towards the front of the motor. Will that matter??
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Old 12th-July-2010, 01:00 PM   #15
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Quote:
Originally Posted by wcjames01 View Post
If the cap isn't sealed it would not be getting the correct pressure. My tank also only has the filling spout and the line out to the pump. That's wht I say this thing has me stumpped. It has to be something very minute. I'm going to put in some SeaFoam today to see if it may be a internal thing. Does it matter which of the two hoses from the PCV valve go to which vacume. My bottom hose goes towards the fire wall and the top hose towards the front of the motor. Will that matter??
WCjames01

Your tank is not under pressure on a car this old. It has to vent to the atmosphere or the pump sucking fuel out of it will create a vacuum in it and fuel will stop coming out to the pump.

I am not sure about the hoses. mine only has one hose to the PCV. Can you post a pic of how yours are hooked up and someone will know.

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