Vapor lock?

[FrankWest]

Originally Posted by Flathead Fever

I was a phone company mechanic for 30-years. We had almost 400 vehicles in our yard, and we kept them for a long-long-time. During that time, I only saw one vehicle experience vapor lock. It was a Chevy Suburban that went up into mountains. When it was around 5000' elevation, on a very hot day, it would just quit. The driver would let it sit for a while and then it fired right up. We'd go up and get it, drive it down the hill to the shop which was at around 1000' elevation where our yard was at, and we never had a problem with it. We worked 4pm to 11:30pm, so by the time we took it back up to its parking spot in the mountains it had cooled down, we could not duplicate the problem. So, we started throwing parts at it, ignition module, coil and everything else we could think of. Still every once in a while, the Suburban would quit but just up at higher elevation in the mountains. One time I was taking it back up the mountain and it was still hot out and it quit, just like it ran out of gas, I pulled over and poured some water on the fuel pump and it started right up. I took it back to the shop and put a fuel pressure gauge on it and it was down just one pound of pressure from the 5 to 6 lbs. specifications. Replaced the pump and that fixed it. That was a form of vapor lock from the high altitude, but the problem was the fuel pump. The thing is it had run all those years without any problems, so you don't want to go redesigning everything you just need to find the problem, sometimes it just kicks your butt. I've had stuff in fuel tanks that after driven for a long time it would get sucked up against the outlet hose and the engine would die. As soon as the vacuum was gone it would unplug itself and drive for a while longer.

On my dad's flathead powered '32 roadster I've taken a 5-gallon can of gas and a 1 1/2 lb. electric fuel pump. stuck it in the cab and bypassed the entire fuel system. That way I knew for sure if it's a fuel problem (be careful). I have the tank out of it right now, it was full of junk. And then I had a stroke, so it hasn't gone back together yet. You could tee in a pressure gauge on the output side of the pump and see what the pressure is when you first start it and then what it is when it quits.

Thank for taking time to give details. I learned a lot from you and will continue to troubleshoot.