Was this a vapor lock?

[Sam Buchanan]

18 minutes ago, harmony said:

Thanks guys but at times I'm a little thick headed.  I'm not understanding why if the carb percolated this one time.  Why only this time?  Why not every time I stop to get gas or stop to buy a poverty pack of beer after a nice long drive?

 

You seem to be missing the key element we are all stating about the starting difficulty. You stated it yourself in your original post.

 

"About 15 minutes later I tried to start the old girl"

 

The key here is "15 minutes". Go back and read our posts about fuel percolation to see how this is relevant. 

[harmony]

5 minutes ago, Sam Buchanan said:

 

You seem to be missing the key element we are all stating about the starting difficulty. You stated it yourself in your original post.

 

"About 15 minutes later I tried to start the old girl"

 

The key here is "15 minutes". Go back and read our posts about fuel percolation to see how this is relevant. 

That's about the length of time it takes from shut down to start up at the gas pumps and at the beer store. Which I do consistently week after week month after month for 3 years ????

[keithb7]

These fuel and heat discussions have raged on so many times. All our questions are not fully answered nor settled in our minds. 

Winter fuel. Summer fuel. Percolation. Vapor lock. Mechanical pumps. Electric pumps. Float level. Choke action. Flooding. 
Timing advance. 6V cranking speed. Heat shields. Ethanol fuel. Compression. Valve sets. Ambient air temps. On and on, the variables keep coming in. 
 

Controlled testing. Monitoring. Take Notes. Will all help sort your particular situation out. I believe all situations are unique. 

[harmony]

If I understand correct about the 15 min. boiling theory,,,  Is that "about" the length of time it takes from the time the engine is shut down ( stop burning fuel) and the gas then reaches boiling point in the carb?  After that time frame it then starts to cool down and it stops boiling?

 

In a case like that, when the gas is boiling, is it possible for  the fuel to be sucked out of the fuel filter and into the carb? ( engine not running)

 

But this still wouldn't explain, that while I'm holding down the start button the gas isn't being drawn up into the empty fuel filter.

Edited April 8, 2022 by harmony

[Sam Buchanan]

1 hour ago, harmony said:

If I understand correct about the 15 min. boiling theory,,,  Is that "about" the length of time it takes from the time the engine is shut down ( stop burning fuel) and the gas then reaches boiling point in the carb?  After that time frame it then starts to cool down and it stops boiling?

 

In a case like that, when the gas is boiling, is it possible for  the fuel to be sucked out of the fuel filter and into the carb? ( engine not running)

 

But this still wouldn't explain, that while I'm holding down the start button the gas isn't being drawn up into the empty fuel filter.

 

I don't have definitive answers, but I can speculate with the best. 

 

I suspect that under the right (wrong) conditions the fuel begins to vaporize in the carb soon after a hot engine is shut down. This occurs because cool fuel is no longer flowing into the bowl and temps rapidly ramp up. The vapors have to go somewhere so they exit the carb and begin cooling back into the liquid phase. The liquid fuel then puddles in the intake manifold and we have a scenario where the air/fuel mixture is incorrect until enough air is drawn into the manifold to begin evaporating the the puddle. This causes longer cranking than we see when the puddle isn't there. Winter gas could make this situation worse since it boils at a lower temp (higher vapor pressure). There have been many times with the P15 and other carbed cars that I've noticed fuel odor after a hot shutdown and this is a sure sign of fuel boiling off in the carb (assuming there are no leaks). The reason the car starts better after an hour is probably due to the puddle in the manifold having evaporated.

 

I don't have much to add concerning the lack of fuel in the filter unless it was also hot enough to promote the gas boiling off as vapor. Since it has no place to go except into the carb it just makes the problem worse. It might be that you had a "worse case scenario" where high temps and a very "winterish" blend of gas came together. But I'm just speculating..... 

[Tom Skinner]

Sounds like Corn Fuel gotcha agin. You'all needs to get non-ethanol fuel, or dump Marvel Mystery Oil into the gas to make her settle down a spell.

Thissun is how we do it down South, knock the heat down, or git some wooden clothes pins on the gas line goin to the carb.

She'll start like a gun shot then.

Tom

[Bryan]

Hmmmm - TEC1-12704 12V 37W Heatsink Thermoelectric Cooler Cooling Peltier Plate Module - Walmart.com     2 Pieces XH-W3001 Digital LED Temperature Controller Module Digital Thermostat Switch with Waterproof Probe Programmable Heating Cooling Electronic Thermostat Range from -50? to 110? (12V 10A 120W): Amazon.com: Industrial & Scientific 

 

Or maybe one of these with the above switch. https://www.amazon.com/heatsink-fan/s?k=heatsink+fan  Imagine that attached to the side of your carb ?

 

Even have a 6V model.  Amazon.com: CNBTR 20mm x 20mm White TES1-4902 Semiconductor 6V 2A Tablet Cooling Chip Peltier : Electronics

Edited April 8, 2022 by Bryan

[harmony]

2 hours ago, Tom Skinner said:

Sounds like Corn Fuel gotcha agin. You'all needs to get non-ethanol fuel, or dump Marvel Mystery Oil into the gas to make her settle down a spell.

Thissun is how we do it down South, knock the heat down, or git some wooden clothes pins on the gas line goin to the carb.

She'll start like a gun shot then.

Tom

We have 94 octane non-ethanol up here and that's all I use.

[harmony]

Well she fired right up instantly this morning as soon as I hit the button the old girl began purrring instantly as if yesterdays event was just a figment of my imagination.

So as Keith suggest if this should ever happen again, I won't go into panic mode and take the recovery one step at a time, starting with, crawling into the back seat and having a nap for a half hour or more to start with.

The moment I saw that empty fuel filter my first assumption was that I rock had hit the fuel line and punctured it. 

 

Oh btw, while it's on my mind and it's sort of topic related.

Some guys add a Phenolic spacer about 3/4" or so between the base of the carb and the manifold.  To help with the cooling effect.  My carb mounting studs are barely long enough to get two gaskets between the carb and manifold as it is.  So my question is where do I get longer studs?  Are they course threading going into the manifold? Is it likely that I will have a lot of grief getting the existing studs out to replace them with longer studs ? Will ATF/brake fluid free them up?  Or would I need heat? 

 

Where do I get that material?  I'm fine creating my own, with the grove on the bottom to match the gasket.

 

Edited April 9, 2022 by harmony

[keithb7]

I have a phenolic spacer here that I had a friend cut for me. I’ve yet to try it. It will lift everything higher.

 

New challenges include but are not limited to:

 

Rigid fuel line to the carb no longer fits. 

Sisson choke linkage issues. Now too short. 
Longer mounting studs needed. 
Throttle linkage needs customization.

Not the least, the engine torque curve changes with the new venturi spacing!   Vroom. Vroom!


 

[harmony]

11 minutes ago, keithb7 said:

I have a phenolic spacer here that I had a friend cut for me. I’ve yet to try it. It will lift everything higher.

 

New challenges include but are not limited to:

 

Rigid fuel line to the carb no longer fits. 

Sisson choke linkage issues. Now too short. 
Longer mounting studs needed. 
Throttle linkage needs customization.

Not the least, the engine torque curve changes with the new venturi spacing!   Vroom. Vroom!


 

hummmm, all good points, as well as the arm holding the air cleaner would have to be longer as well.

[keithb7]

Vacuum advance line doesn’t fit any more!

 

 

Edited April 9, 2022 by keithb7