Hey guys i was just wondering if anyone has a problem with their vette vapor locking?

 

EFI engines DON'T vapor lock.

RACE ON!!!

 

The fuel line is under about 40 psi and vapor lock is just about impossible at that pressure.

 

 

Last time I got locked up, had the vapors something awful!

 

They CAN'T vapor lock.

 

You have another problem and not a vapor lock.

 

Vapor lock? I got no stinkin' vapor lock.

 

I hate to tell you this but vapor lock can occur in EFI engines. But it is highly unlikely in a stock or even modified C4. I had a highly modified 57 Chev Belair that I was tuning that was equipped with a 447 stroked small block with a rather large cam, and a Super Ram intake. The engine compartment was highly detailed and was pretty much sealed up it wasn't very good as far as air flow goes. Also he had a custom made aluminum fuel tank with two large fuel pumps running in the tank.

On one test drive we drove the car about 20 miles during a tuning session. We pulled off the freeway and into a Chevron parking lot, stopped the engine for about 10 minutes for me to make some changes to the file. Upon start up, the engine ran like it was running out of gas, sputtering and dying. I checked several things thinking there was some other problem. One problem I noticed was that the fuel tank was very HOT to the touch. I mean it was so hot that if it was a hot tub I would be very hesitant to get in. It took several tries before we could get it running good enough to get it on the road back towards the shop.

We got about 10 miles from the gas station before she crapped out again. I called our shop to have someone bring 5 gallons of fuel out which came in 10 minutes. Once she got a load of cool fuel she started right up and purred like a kitten. Once back in the shop I got the car to act up again. I had a fuel pressure gauge on the line and was able to drain fuel out to see what kind of volume that pump(s) were pushing through, much to my suprise I was actually getting lots of bubbles through the clear plastic drain line. I figured at that point the fuel was literally boiling in the lines. As I knew there was plenty of fuel in the tank and that the pick up was completely submerged.

The heat was not coming from the surrounding enviroment, meaning it didn't come from being to close to the exhaust system, because this tank was inside the trunk of the car. The heat was coming from the engine compartment from the reciruclating fuel from the return line. He had a 5/8 line for a fuel feed and a 1/2" for a return line. Both lines were at the same temperature as the tank.

I ended up removing the two large pumps and installing a single Accel EFI pump suitable for his application. I attributed the problem to the large volume of recirculating fuel picking up heat from the engine compartment with every round trip back to the tank. Once we made that change the car never had a problem again. And the fuel tank temperature dropped to half of what it was. If that wasn't vapor lock I have no idea what you can call it.

 

As an engineer I worked with an engineer that worked directly on the fuel injection system for corvette. They had issues with vapor lock and the car would backfire, not start, and cause havoc with engine idle and performance.

So I believe that under the right conditions vapor lock is possible however typically unlikely with todays tuning methods and techniques.

Chris

 

On my 88 I had what might appear to be vapor lock, it was the IAC!


seeya

 

I get vapor lock in my throttle body injection Ford. slow fuel flow, due to a poor pump, partially clogged filter will let the fuel heat up more in the lines. It sucks having to shut it down and wait a half hour or so for the engine compartment to cool down.