Iwas driving last Sunday here in "Sandy Ego" lots of stop and go for about 25 miles..all car fluid temps were normal and nominal..Ambient air temp was in the 90's.

I came to a stop sight and stopped....Placed the car in 1st and tried to accelerate away..what I got was abad studdering like teh car was driving on two cylinders..the car was barely running...I got pulled over off teh road...looked under the hood...realized my cell phone battery was dead...I got back in the car said a prayer..the car came to life like nothing had happened..elapsed time ~5 min....

Was it Vapor lock..or just bad luck

 

I didn't think vapor lock happened while running

My LS powered truck has done nearly the same thing you describe on three occasions, but never my vette. :doubleshrug:

 

You can't get a vapor lock when you use a tank mounted electric fuel pump. The line for electronic fuel injection is pressurized.

 

EXCELLENT INFORMATION!!! I did not know that! Although I really don't know much about vapor lock either.

 

This is how a Vapor Lock is caused and why.:

Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

 

So it sound like it could have been locked.....or somthing worse....

 

Haven't heard of vapor lock problems in years. I doubt you had vapor lock with a tank mounted pump as the pump is right in the liquid gasoline and the fuel line is pressurized to a pretty high pressure. Vapor lock usually occurs in carbureted cars where the fuel pump is located on the engine and uses a vacuum to pull gasoline from the tank. As the gasoline heats in the fuel line it vaporizes and the pump is trying to pump vapors to the carb Vs liquid. That is why some of the older cars had gasoline return lines that routed gasoline back to the tank. That way the gas was continually flowing and didn't vaporize as easily. People who race/raced those old cars would install electric fuel pumps in the tank to get around the problem also.

Bill

 

Correct. In the old carbureted cars with the fuel being sucked from the gas tank, you could get air in the line or the fuel would vaporize (hence the name) within the line. When it got to the carburetor, it wouldn't be a steady stream of fuel but instead would be spurts of fuel interrupted by vaporized fuel and you'd get severe hesitation.

You can't get that in modern fuel injected cars. The fuel lines are pressurized from the tank all the way to the fuel injectors. Any "vapor pockets" would immediately be compressed and eliminated by the pressure.

 

i believe i would check the codes there are probably some history codes that will tell the tale.

 

Hey guys, just a minor footnote to add...

(for those of you looking for Cliff's notes, here they are... vapor lock is not likely to occur on a stock C5 but it *IS* possible on a fuel injected vehicle, depending on pump placement, ambient heat, and fuel requirements of the motor vs. fuel delivered by the pump)

Vapor lock can still occur in fuel injected vehicles, but maybe not in the sense it was thought of in carbed vehicles, and it is certainly not common. Just check out the guys in the forced induction forum who are pushing their fuel systems to the limit -- we have all become well aware (at least those of us in warm climates) of the impact that heat has on fuel delivery.

For example, under boost, when a car is cool, it may hold 58psi solid through redline. But once the fuel gets hot, it is not uncommon to see 10psi pressure drops in fuel pressure. How much of that is due to what may be happening mechanically with the pump (e.g., heat causing parts to expand and not work as efficiently as they did before) and how much of that is due to the physical properties of the gasoline is difficult to determine, but go to the gas station and add a few gallons of cold fuel that's been sitting underground and watch the pressure dip go away.

Furthermore, I had a highly modded 2002 FI convertible I was trying to deliver a lot of fuel to. I tried a few different things, including a large external pump. It was an Aeromotive 11104, one of the largest "street" pumps you can get. It was sucking fuel from a bulkhead fitting at the very bottom of the tank with the pump mounted almost all the way near the bottom of the tank.

After an hour of IDLING the pump would heat the fuel so much that fuel pressure would drop and drop and drop until it was too low to run the car. This is with a full tank of fuel. At one point we even opened one of the fittings at the front of the car's fuel system to see what was happening, and more air than gasoline came out. Using an IR thermometer to measure the temperature of the fuel/rails/tank, it was evident the fuel was boiling -- some temps were over 180 degrees. Basically, what was happening is that the majority of the fuel being pumped to the motor at idle was hitting the fuel rails (which were aluminum, and soaked up a lot of heat) and then being returned, because the car did not need that much fuel. Add on to that the heat of needlessly compressing the fuel (heat generated by the pump) and within an hour, things were getting toasty.

Since the bulkhead fitting was always submerged, the only explanation that made sense was that the fuel was boiling and becoming enriched with oxygen, which the pump was subsequently sucking in and pushing to the rails. Once the car cooled down it would operate normally again.

Tangentially, although I have never measured fuel tank vacuum, we do know that modern vehicles attempt to maintain a slight vacuum on the tank to prevent hydrocarbon emissions. Remember what we learned about boiling points and pressure (e.g., the boiling point of fluid in your radiator is raised because your cooling system is pressurized... so what happens to fuel in the tank because there's a slight vacuum on it?) When I read up on it a while back, it seemed there were varying opinions on when gasoline boiled, but there were a lot of documents that suggested it could start boiling somewhere between 140 degrees F and 160 degrees F. That's not hard to reach at all in our cars.

There's more data at this old thread I made (link below) but here's a graph that shows various fuel system component temps using a modified fuel system with more fuel flow (OEM fuel pump + external fuel pump). Again, not likely to happen on a stock car but simple modifications to add extra flow to the system can quickly get those temps up!



Thread: http://forums.corvetteforum.com/show....php?t=1415268