<VV> Re: Vapor lock, was Self pity and whining

[norman.witte at comcast.net]

Frank, thanks for confirming what I thought.  It sure is good to at least have an idea what the problem is.  I don't think I was clear that this was a turbo in my original post.  

I think I am going to try bending the fuel lines so that they are up from the shroud a little higher.  Any other suggestions to cure this?  I should mention that I put in about 9 gallons of premium ($30!!!) last Saturday.  Whether they have changed formulas in Lansing at Speedway, I have no idea.

Norm 
-------------- Original message -------------- 
From: Frank DuVal <corvairduval at cox.net> 

> 
> 
> norman.Witte at comcast.net wrote: 
> 
> > 
> >Anyway, tonight I came home from work, grabbed the convertible, and went back 
> to the office to get some work done. Last fall the car had this problem where 
> if you drove it for awhile and then parked it for a short time, it would start, 
> but then sputter to a stop. 
> > 
> 
> Classic vapor lock. 
> 
> > Then you could crank it and it would act like it was going to start, but it 
> wouldn't stay running. Then, suddenly, it would fire and run. Over the winter 
> the carb was rebuilt and I thought this problem was licked. 
> > 
> > 
> . 
> Carb rebuilding should have no effect on vapor lock. Carbs use liquid 
> gasoline to flow through the orifices until it atomizes in the venturi. 
> Vapor does not flow properly in a carb. 
> 
> >I was wrong. I drove from the office to church to pick up my son from youth 
> group. In a repeat of the one other time I used it to pick him up from youth 
> group, we got about half a mile and the dang thing died on me. My wife came and 
> picked us up and the car is sitting in a parking lot. 
> > 
> >I can't for the life of me figure out what is wrong. It seems to be getting 
> some spark, because it will briefly catch and stutter. I don't think the 
> Pertronix is bad because I can't see how that would relate to shutting the car 
> down. I think its not getting enough gas because I can pump the accelerator 
> heavily, and it doesn't flood, it just does the same sputtery thing. I thought 
> about vapor lock--I don't know much about it--but I thought that required hot 
> weather, and tonight it was fairly mild, maybe in the upper sixties. 
> > 
> > 
> 
> The temperature needs to be high enough to boil the liquid fuel. Tony U. 
> mentioned winter blends still being in your tank. This winter fuel boils 
> at a lower temperature. 
> 
> The other BIG clue is the "hot soak" period required to cause the 
> problem, hence the "classic vapor lock" symptoms. When you park the car, 
> the engine is warm and the fan is nolonger cooling the engine, so the 
> temperature of the engine compartment rises because the engine is warm. 
> This heat gets into the fuel especially in the fuel pump as it is 
> physically connected to the engine and a thermal path exists. So if you 
> kept driving, the fan would keep the fuel cool. If you parked longer, 
> the heat would dissapate through the body sheet metal and other paths 
> (convection, radiation) thus the fuel would again be cooler and 
> therefore a liquid. 
> 
> Electronic components can also exihibit a hot soak condition as some are 
> susectable to heat problems when they are defective. 
> 
> A fuel pump can pump vapor, but the quantity of vapor available from 
> boiling fuel is way more than the pump can handle. I mean say 1 cc of 
> liquid fuel when vaporized occupies way more than 1cc of volume. And the 
> pump is pulling a vacuum on its suction side, so the pressure is lower 
> and the liquid boils into a vapor at a lower temperature than on the 
> pressure side. Too technical now? 
> 
> The roadside cure for vapor lock is to pour your iced drink on the fuel 
> pump and input line to the fuel pump. Once the vapor is condensed back 
> into a liquid in the pump, great volumes of liquid fuel can be pumped 
> through the vaporized line and carb to get liquid fuel to the carb 
> passages and it will start and run. 
> 
> The carb fuel bowl usually does not run dry during a hot soak period, 
> which is why the car starts and runs until the bowl goes dry of liquid 
> and just has vapor in it. 
> 
> If ice cubes on the fuel pump make the car start, then it is vapor lock. 
> 
> Frank DuVal