The Stovebolt Site Forums The Shop Area Engine Shop Vapor Lock?

While I do own two Chevy trucks (56 Apache w/235 and 59 Apache w/283) I also own a 66 Caddy that had a problem that I hoped this group might find interesting.

Caddy has run great recently. Tuned up, new plugs, new carb, fuel pump, gas tank and sending unit. Its been running like a champ until yesterday when suddenly, while I was driving, it just stalled out and wouldn't start again. Checked the spark at distributor and had plenty of spark. But it wasn't getting gas. No gas was in the glass bowl of the fuel filter housing. Given all the new stuff I replaced I am stumped as to why it isn't getting gas. Tank is half full. A friend suggested vapor lock but I don't really know what that is. I also suppose that the new fuel pump could be bad.
Any other thoughts? Thanks, I have always appreciated advice that I receive on this board.

Ray, vapor lock is when the liquid fuel in the line from the pump gets so hot it vaporizes before it gets to the carb so the engine starves - I'd suspect a new fuel pump first, seems there's a high rate of defects nowadays

Bill

Thx Bill. I fear you may be correct. I might put the old pump back on til I get a new one. Your advice is always appreciated.

I had a similar problem on one of big trucks. The truck just stopped running, like it ran out of fuel, I still had a half of tank of fuel! I would put 5 gallons of fuel in and it started right up but when it got back to a half of tank it died again. Turns out the rubber fuel line from the tank selector valve to the fuel filter was loose. The pump was sucking air and not fuel. I guess it worked "harder" pulling up fuel from a 50 gallon saddle tank that was half full. Put a new rubber line and new clamps and problem solved. So check all your fittings.

John G

My experience with vapor lock has been that it is caused by poor original design (like my 83 Trans am), internal engine problem causing extreme dissipation of heat, modification of the vehicle affecting air flow, or the already mentioned fuel line/pump failure. It is pretty rare to just start to happen and other causes need to be investigated.

Make sure your gas caps are vented on these old stovebolts. And Ray Fischer your 66 Caddy may very well need a vented gas cap as well.

I had a 66 Pontiac with a 389 that would run a while and stall out. After it sat a bit it would drive a while and quit. I also replaced the fuel pump since it was not pumping fuel. New rubber lines where they were needed. Blew the lines out and could hear the bubbles in the tank.

One day I bought a new vented gas cap for it and it ran fine after that. Seems the original cap had the vent blocked by dirt.

Just another thought.

I'll try that as well. It usually is the simple stuff that causes problems. My first reaction is often to go for the esoteric.