Carb question on a 78
Thread Starter
Instructor
Joined: Jun 2004
Posts: 110
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From: Bozeman MT
Carb question on a 78
Hello,
My 78 QJet leaks fuel out of the floats when the car sits for a day or so. I plan on pulling the carb off and sealing the plugs with the oven and JB weld approach this winter. But, here is my question: The car will not start. No fuel squirts because there is none in the bowls. Doesn't matter how long I crank, none gets there. I replaced the fuel pump as I thought that was the problem, but still does not start. When I squire a little fuel in by hand, it fires right up and runs fine.
Why is there no fuel pumped up to the floats and squirting out when I crank the engine?
-Kev
My 78 QJet leaks fuel out of the floats when the car sits for a day or so. I plan on pulling the carb off and sealing the plugs with the oven and JB weld approach this winter. But, here is my question: The car will not start. No fuel squirts because there is none in the bowls. Doesn't matter how long I crank, none gets there. I replaced the fuel pump as I thought that was the problem, but still does not start. When I squire a little fuel in by hand, it fires right up and runs fine.
Why is there no fuel pumped up to the floats and squirting out when I crank the engine?
-Kev
Burning Brakes
Joined: Nov 2005
Posts: 1,143
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From: Leander Texas
Fuel is drafted into the engine by vacume when the engine is cranked or running. You should see Fuel "squirt" into the Venturi when the accelerator is pressed. Is this not occuring? If this doesn't happen you could have a faulty accelerator pump, You could need a new fuel filter, or your carb may need to be rebuilt.
Thread Starter
Instructor
Joined: Jun 2004
Posts: 110
Likes: 0
From: Bozeman MT
Hi, Carb was rebuilt a year and a half ago. Once the engine is running, the accellerator pump works just fine, as fuel squirts into the venturi. It just does not do that after the car has sat for a while, and does not do it until you manually squirt fuel in when cranking.
I am just puzzled as to why there is no fuel squirting until it actually runs.
I am just puzzled as to why there is no fuel squirting until it actually runs.
Drifting
Joined: Feb 2005
Posts: 1,438
Likes: 2
From: Melrose Florida
It sounds like you have a fitting that leaks air, at the carb, the fuel line to the carb, or at the fuel pump.
Pouring gas in the carb provides enough vacuum to restart the "siphon" of gas from the fuel pump, and then the fuel pump is pumping a column of gas...fuel pumps and most kinds of fluid pumps do not pump air well.
Your line/fitting leak is letting the gas fall away from the carb and to or past the fuel pump. Typically, even after long periods without use, fuel remains at the fuel pump and in the fuel line to the carb, so cranking moves fuel to the carb.
I know you mentioned "fuel leaking from the floats" (whatever that means), but I still think you have another perhaps additional problem.
Steve
Pouring gas in the carb provides enough vacuum to restart the "siphon" of gas from the fuel pump, and then the fuel pump is pumping a column of gas...fuel pumps and most kinds of fluid pumps do not pump air well.
Your line/fitting leak is letting the gas fall away from the carb and to or past the fuel pump. Typically, even after long periods without use, fuel remains at the fuel pump and in the fuel line to the carb, so cranking moves fuel to the carb.
I know you mentioned "fuel leaking from the floats" (whatever that means), but I still think you have another perhaps additional problem.
Steve
