Serious Vapor Lock
01-06-2019, 03:44 PM
#1
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Car: 1986 IROC-Z
Engine: 305 LG4 Carbed
Transmission: T5 5-Speed
Axle/Gears: 7.5 10-Bolt 3.42
Serious Vapor Lock
I’ve got an ‘86 LG4 that quits if I drive it on a warm day, shut the engine off for a few minutes and then drive it again. I had it die on me once as I left the gas station. I found that I could start it immediately if I pour cold water on the fuel line leading to the fuel pump. I minimized the problem by insulating the fuel line. The exhaust manifold isn’t far away and gets as hot as 500 degrees. How did these cars ever leave the factory like this? It doesn’t get that warm where I live. Is there supposed to be some kind of a shield on the exhaust or fuel line side to prevent the heat from warming up the fuel? Is there anyone selling something similar to GM’s part # 14085385 low pressure helper pump kit? There doesn’t appear to be any restriction from the tank to the pump. Flows plenty of fuel when cold.
01-06-2019, 03:59 PM
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Re: Serious Vapor Lock
Your problem isn't"vapor lock". It's the EXACT OPPOSITE of vapor lock.
It is the LIQUID fuel getting hot and forcing too much of itself into the carb, at which point it boils into a foam like a shaken-up Diet Coke, and spewing out of every hole in the carb.
Insulate the fuel pump from the block to solve it. 2 gaskets usually does the trick.
It's also not about how the car left the factory. It's about how fuel today is quite a bit different from what our antique cars were born into.
It is the LIQUID fuel getting hot and forcing too much of itself into the carb, at which point it boils into a foam like a shaken-up Diet Coke, and spewing out of every hole in the carb.
Insulate the fuel pump from the block to solve it. 2 gaskets usually does the trick.
It's also not about how the car left the factory. It's about how fuel today is quite a bit different from what our antique cars were born into.
01-06-2019, 04:13 PM
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Car: 1986 IROC-Z
Engine: 305 LG4 Carbed
Transmission: T5 5-Speed
Axle/Gears: 7.5 10-Bolt 3.42
Re: Serious Vapor Lock
Your problem isn't"vapor lock". It's the EXACT OPPOSITE of vapor lock.
It is the LIQUID fuel getting hot and forcing too much of itself into the carb, at which point it boils into a foam like a shaken-up Diet Coke, and spewing out of every hole in the carb.
Insulate the fuel pump from the block to solve it. 2 gaskets usually does the trick.
It's also not about how the car left the factory. It's about how fuel today is quite a bit different from what our antique cars were born into.
It is the LIQUID fuel getting hot and forcing too much of itself into the carb, at which point it boils into a foam like a shaken-up Diet Coke, and spewing out of every hole in the carb.
Insulate the fuel pump from the block to solve it. 2 gaskets usually does the trick.
It's also not about how the car left the factory. It's about how fuel today is quite a bit different from what our antique cars were born into.
01-06-2019, 04:36 PM
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Car: 1987 SC/1985 TA
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Re: Serious Vapor Lock
the fuel lines can be insulated but your problem should not be quite so persistent.
the stock pump should recirculate fuel constantly through the lines and alleviate 'vapor lock' under all but severe conditions. your supply line is clear, but is your return line? have you checked the flow of your pump? I've had them fail before where they would barely move fuel (the fulcrum arm in the pump had started to come out of it's peened housing within the pump body-hard to put into words but it was evident upon inspection).
the stock pump should recirculate fuel constantly through the lines and alleviate 'vapor lock' under all but severe conditions. your supply line is clear, but is your return line? have you checked the flow of your pump? I've had them fail before where they would barely move fuel (the fulcrum arm in the pump had started to come out of it's peened housing within the pump body-hard to put into words but it was evident upon inspection).
01-06-2019, 06:35 PM
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Car: 1986 IROC-Z
Engine: 305 LG4 Carbed
Transmission: T5 5-Speed
Axle/Gears: 7.5 10-Bolt 3.42
Re: Serious Vapor Lock
the fuel lines can be insulated but your problem should not be quite so persistent.
the stock pump should recirculate fuel constantly through the lines and alleviate 'vapor lock' under all but severe conditions. your supply line is clear, but is your return line? have you checked the flow of your pump? I've had them fail before where they would barely move fuel (the fulcrum arm in the pump had started to come out of it's peened housing within the pump body-hard to put into words but it was evident upon inspection).
the stock pump should recirculate fuel constantly through the lines and alleviate 'vapor lock' under all but severe conditions. your supply line is clear, but is your return line? have you checked the flow of your pump? I've had them fail before where they would barely move fuel (the fulcrum arm in the pump had started to come out of it's peened housing within the pump body-hard to put into words but it was evident upon inspection).
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