Vapor lock 1990 E350 EFI 460 engine?

What was your fuel level?

Full tank of gas.

With fuel systems pressurized from the tank to the injectors, vapor lock is a thing of the past. Your pressure regulator will bypass the excess fuel and keep the fuel rail cool. A good fuel pump will pump far in excess of your engines needs.

I used to think this, until very recently when I started hearing stories, like the video above, of EFI systems experiencing vapor lock.

It is true that EFI systems are a closed loop and route unused gasoline back to the tank. However, what I am hearing is that it is the Pressure Regulator that controls pressure by determining when and how much fuel to allow to return back to the tank. If your fuel boils in the rail, this pressure regulator evidently can't deal with that and fails to route fuel back to the tank - it senses this vapor as a pressure drop and so restricts/stops flow of fuel back to the tank. This allows the fuel to sit in the rails and get even hotter, resulting in more vapor.

In addition, I am learning that ethanol gasoline has a lower vapor temperature than pure gasoline. This is a 1990 engine. This was designed before the era of ethanol gasoline. It may well be that the system was not designed to handle heat loads with ethanol gasoline's lower vapor temperature.

I'm not saying that is the problem, but, what is the change interval on the fuel filter? Wouldn't it be common sense to replace the filter per the manufacturers recommendations? You have many of the symptoms of low fuel pressure and/or a restricted fuel line(s).

Yes, I agree. Honestly I don't think I've ever replaced the fuel filter in any vehicle I've ever owned, and we buy ours new and drive them about 13-15 years until they are just no good anymore. I've just never given the fuel filter any thought before. But I am going to replace this one for sure. A restriction in the fuel line could result in a decrease in pressure.

Long story a bit shorter we found that the catalytic converter. came apart and got red hot. Changed the converter and the engine picked uppower like before but the engine wouldn't idle right and would die at idle. Finally an ace mechanic found the issues. He said both oxygen sensors were bad which was dumping gas into the exhaust (I was getting 4 1/2 mpg)and burned up the catalytic converter. Also. the throttle position sensor was faulty which allowed the engine to die at idle. Also I found out that there is no way to set the idle speed without going into the computer and resetting it. Good luck.

My cat converter recently died - you could hear a piece of the internal honeycomb banging back and forth with the exhaust beat at idle. So, it has been replaced.

I have no problems idling, other than when the system gets hot as described above in which case it will not run at any throttle position, idle or otherwise. I have run my ODB1 code reader and have a clean bill of health so I do not suspect the O2 sensor at this time. However at 85K it may be due for replacement anyway.

Thanks for all the responses.

Steve