Possible vapor lock or ??? 454 / 496 GM motor

[jeff york]

I had an odd incident last night. I pulled my 1977 Airstream Argosy 454 / 496 GM powered coach out of storage. I ran it about 10 minutes before leaving and then drove about 25 miles and stopped for gas. I pumped about 22 gallons of regular gas into it. It sat maybe 20 more minutes running while I pumped the gas. Then, right after I pulled out, the motor shut down. I got it to restart and then as soon as I got through the intersection it shut down again. I could hit the key and it would sputter and fire up and quickly shut down. I had to pump the heck out of it to try and keep it running. But, it would quit. I took some starting fluid and got it to start again and it quickly shut down. On the second try with starting fluid it started and I drove it about a block to a Walmart parking lot. I shut it off I think. After a few minutes, I started it back up and decided to try and get it home about 4 miles away. It ran just fine the whole way. So, now I am wondering what happened. 

Back ground. I recently replaced my mechanical fuel pump with an electric fuel pump. I test drove it quite a bit before taking it out on the road so I thought everything was ok. I think after it shut off last night I checked the fuel pressure control valve and it may have been set as low as 2-2.5 PSI. It was dark so I am not sure. I pushed it up to 4 PSI and thats when I started it and it ran the rest of the way home. However, it ran fine for the first 20 plus miles and probably an hour. Its a Rochester Quadrajet carb. The fuel lines at the motor I changed to flexible neoprine ( I think) and on the mechanical pump it was a hard line from the mechanical to the carb. AS per electric fuel pump installation, I placed a pre filter in front of the pump to filter large particles and a new filter to filter small particles at the carb. 

There is no return line on the electric pump. 

So, did I get vapor lock ? Odd this happened right after re-fueling. Was my fuel pressure set to low ? Do I need to add something to insulate the gas lines from heat to prevent vapor lock ? Do I need to add stand offs on the fuel line to get them farther from the engine to stop heat soak ? The fuel line sits pretty close to the intake manifold and the valve cover. Sorry for the lenght. Just trying to throw out all the details.  

[Russell E Johnson]

From my experience with the quadrajet on our 454 is that at a certain temp the choke will try to engage even tough everything is hot enough.  It is real annoying but it acts very much the way you are describing