Ok.I have a hopped up 3.8 V6 in my 1994 Taurus wagon.I have a low end cam in it,a better flowing intake,a hypo chip,and a K&N filter.The bottom end and the heads have been reworked and also hooked up a Flowmaster exhaust.In case you are wondering I built it as a sleeper for off the line stuff only,redlight to redlight.I got sick and tired of the rice burners and the kids that drive them.I will post a couple pics to my album if you would like to see it.Anyway for the first month it ran great but yesterday it stalled on my wife.She called me to come get her.After a minute of checking on the side of the road I realized it was a fuel delivery problem.What I did was go to the fuel rail and release the pressure.Once I did that it fired right up.I drove it about a mile or so and it did it again.I released it again and again it started right up.I drove it the rest of the way home,each time doing the same thing.I tried not releasing the pressure and instead just waiting but it won't restart unless I release that pressure.I replaced the Fuel pressure regulator but that did not fix it.I also tried the fuel filter but still no good.I tested it several times and it will absolutly not start until I release the pressure off the fuel rail.Vapor lock?Any ideas?

 

These cars constantly re-circulate fuel back to the tank. This is how vapor-lock is prevented. I believe your problem is not so much fuel delivery but fuel return. Unfortunately, I am not familiar with the routing and valving of your fuel system. If I were you I would make sure this return system is working correctly. Hope this points you toward the problem area. Good luck.

 

my only 2 occurances ok actually three of vapor lock are.

1992 chevy corsica- vapor locked one day during the summer (aunt and uncles car) we had that thing loaded full of people and luggage and barely made it to the hotel before it started doing that.

1993 dodge caravan- pretty much same thing during a hot summer day

1995 ford taurus w/ 3.8 L - dad and i were going through st. louis and it was atleast 95 degrees that day. lets just say we vapor locked from st. louis to home (which at that time was versailles, mo) we stopped and did a car wash which cooled the car down for quite awhile but eventually it came back.

honestly the only thing i could think of is try to get that motor cooled down more and if you vapor lock, turning off the a/c helps quite abit but you'll sweat the rest of the time.

 

When you released the pressure, was it really vapor (air bubbles) or just liquid?

I'd check the evaporative return system, the charcoal canister, it's solenoids/valves, etc. The fuel should return to the tank.

Did you try cracking the gas cap and see if there's a vacuum (or lots of pressure) ?

 

I would have to say it was some other problem with fuel return or some other overheated component not "vapor lock". An engine would have to get very hot to vapor lock with the fuel pressure that is used in an EFI system. The bypass pressure regulator constantly circulates fuel back to the gas tank which keeps the fuel cool in the fuel rail. If the return line is partially blocked or the pressure regulator fails closed the fuel pressure would increase rapidly flooding the engine.

 

When I release the pressure gas comes out first and then a mixture of gas and air.I did try removing the gas cap but no pressure or vacume at all.I thought maybe it was vapor locking from the heat so in an attempt to get the engine to run cooler I removed the thermostat and flushed the radiator.It still did it.I am pretty confused now.When you first start the car in the morning it will run fine for 20 minutes or so,Then slowly you can hear the enging start to stumble before eventually stalling.Once it stalls I release the pressure and it restarts fine,But now that it's warm it will only run for roughly 3-5 minutes before stalling.That seems to indicate vapor locking due to heat because when it's cool like in the morning it runs for 20 minutes or so,but once it gets warmed up it only runs for 5 minutes max before I need to release the pressure.If it were a fuel return problem would'nt it still have a problem hot or cold?I guess it is conceiveable that somewhere in the emmissions crap that there might be a sensor or some type of valve that is supposed to receive a signal to open once the engine reachs operating tempature but for some reason is failing or not receiving the signal.I don't know that much about that end of it.

 

How much gas is in the tank? Is the pump sucking air?