Register now to get rid of these ads!

Vapor lock quick fix???

Discussion in 'The Hokey Ass Message Board' started by speedo, Apr 8, 2005.

  1. speedo
    Joined: Jul 4, 2001
    Posts: 74

    from Dayton,OH

    I have a 66 Caddy at the shop, complaint is that when it gets hot, the fuel is cutting out, fuel box is empty. After about 10 minutes or so, it fires up again and the bowl is full. I checked the main line into the pump, from the tank and it was cracked and I replaced it.....

    Now here's the problem, it doesn't die now, but you can tell that it is still running out of or low on fuel. I just replaced the pump, last summer, due to a service manager that thinks that's the problem, and wants me to do it again. I hate to charge the guy for a pump again. I can't see how a pump would shut down when it's hot, they just don't do that. A mechanicla pump, is just that, it either works or it doesn't........

    It has the symptoms of vapor lock, it sounds like. Just not sure if there's a quick and dirty way to check.

    Anybody run into this?
  2. J.D.
    Joined: Oct 1, 2004
    Posts: 788


    My '64 Lincoln did it right after I replaced the fuel pump (wans't running before hand) I just ran a electric pump in line back at the tank so when it started cutting out I just click it on and go on my way (kills the gas milage when it's on). I always just figured my fuel lines had some build up in them or something not letting the fuel flow properly. Good Luck
  3. 4woody
    Joined: Sep 4, 2002
    Posts: 1,966


    Wrap the fuel line near the engine and exhaust with Thermo Tec or similiar heat shield. If it is vapor lock it'll make a noticable difference.
  4. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,624


    make sure the gas cap is good and will relieve pressure and vacuum.
    Register now to get rid of these ads!

  5. check the entire line for leaks/splits as that would do same thing..also the problem could be in the tank at the pickup tube/sock /screen?

    I have taken tanks apart and cleaned em and the tube was clogged with rusty plaque type substance- very hard to clean out too.......
  6. 61bone
    Joined: Feb 12, 2005
    Posts: 890


    Vapor lock doesn't happen between the pump and the carb, it happens between the tank and the pump. The suction of the pump lowers the pressure in the line and a t the same time lowers the evaporation point of the fuel. So if you have a restriction or a hot spot in the line the fuel evaporates before it gets to the pump. The pump won't pump enough vapors to run the engine.
    So check for areas where the line runs close to the exhaust system or lays downstream of heat from the exhaust. Best way: drive it till it falters, crawl underneath and run your hand down the fuel line feeling for hot spots. They'll be easy to find.
    Check for restrictions: smashed lines, plugged lines, plugged pickup filters and the most insidious of them all the deteriorated rubber line on top of the tank.
    Get the flow specs for your car and check the fuel pump output cold. If it's not to spec see above before you replace the pump. While a new pump may cure the problem it is likely due to other causes and will recur if the pump you have is fairly new and will pump to spec from a container that eliminates the present fuel system. Disable the ignition. Take your emergency fuel supply can and a short piece of the proper size hose and hook to the inlet side of the pump. Another piece of hose on outlet into a graduated container. Crank for specified time and measure output
    If the pump fails both tests replace it. If not, the problem is one of the above.
    happy cruzin

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2013 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.