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Old 04-08-2005, 06:24 PM   #1
speedo
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Default Vapor lock quick fix???

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?
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Old 04-08-2005, 06:30 PM   #2
J.D.
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Default Re: Vapor lock quick fix???

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
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Old 04-08-2005, 06:57 PM   #3
4woody
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Default Re: Vapor lock quick fix???

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.
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Old 04-08-2005, 08:23 PM   #4
stealthcruiser
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Default Re: Vapor lock quick fix???

make sure the gas cap is good and will relieve pressure and vacuum.
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Old 04-08-2005, 08:48 PM   #5
choprods
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Default Re: Vapor lock quick fix???

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.......
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Old 04-08-2005, 09:25 PM   #6
61bone
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Default Re: Vapor lock quick fix???

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
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