The Ford Barn

Tom Bellfoy · 05-19-2015, 08:33 PM

Whats is the significance of the carbs performance when I turn off the gas supply at the shut off valve and the engine idles faster just before the carb runs out of fuel ? Is the carb set too lean or too rich ?

sphanna · 05-19-2015, 08:45 PM

When you empty the carb do to the valve closed, the engine runs leaner just before it quits. You are not running too lean. Maybe or maybe not too rich. If you are running at best fuel to air ratio, what you are experiencing is normal. If you are running too lean you will not get the the slight rpm rise just before it quits. You need that slight rise if you mixture is correct.

Tinker · 05-19-2015, 09:02 PM

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Hit and miss engines will do the same. I'd dare to say it's more oxygen fueling the fire. But it won't contunie to run at that lean of a mixer and will quit idling... if it was just cracked open slightly not just shut off. Hey At least you know the shutoff is working.

05-19-2015, 08:33 PM	#1
Tom Bellfoy Senior Member Join Date: Oct 2010 Location: Cumberland, ON Posts: 252	engine idles faster when gas is shut off Whats is the significance of the carbs performance when I turn off the gas supply at the shut off valve and the engine idles faster just before the carb runs out of fuel ? Is the carb set too lean or too rich ?

05-19-2015, 08:45 PM	#2
sphanna Senior Member Join Date: Jun 2010 Location: Polk City, Iowa Posts: 526	Re: engine idles faster when gas is shut off When you empty the carb do to the valve closed, the engine runs leaner just before it quits. You are not running too lean. Maybe or maybe not too rich. If you are running at best fuel to air ratio, what you are experiencing is normal. If you are running too lean you will not get the the slight rpm rise just before it quits. You need that slight rise if you mixture is correct. __________________ Steve Hanna, Polk City, IA

05-19-2015, 09:02 PM	#3
Tinker Senior Member Join Date: May 2010 Location: MN Posts: 7,053	Re: engine idles faster when gas is shut off Sponsored Links (Register now to hide all advertisements) Hit and miss engines will do the same. I'd dare to say it's more oxygen fueling the fire. But it won't contunie to run at that lean of a mixer and will quit idling... if it was just cracked open slightly not just shut off. Hey At least you know the shutoff is working.