The Ford Barn

Ed in Maine · 05-12-2021, 09:33 AM

What makes a Model A backfire when you turn the key off? Car seems to run OK otherwise. Ed

nkaminar · 05-12-2021, 12:38 PM

Unburnt fuel/air igniting in the hot exhaust manifold, exhaust pipe? There are couple things to try: Let it idle to for a while before turning it off or turn off the fuel and let the carburetor run dry before shutting it off. You can also try pulling the choke to kill the engine then turn it off. Another thing to do, which Model T guys do, is to set the idle so low that the engine dies when the throttle is shut then use the hand throttle to set the idle up enough so that it does not stall when using the car. The advantage with this option is that when descending a hill you can turn the idle down to the point where no fuel/air in getting into the engine.

If it is backfiring through the carburetor then that is a different story and probably due to a leaky intake valve.

dj · 05-12-2021, 03:22 PM

always make sure you retard the spark before shutting down
DEnnis

700rpm · 05-13-2021, 10:55 AM

Dennis, Where did you hear that? I have never heard that advice, nor have I ever done that, and have had no adverse effects in over 50 years of driving Model A’s.

McMimmcs · 05-13-2021, 11:46 AM

[QUOTE=700rpm;2016152]Where did you hear that? I have never heard that advice, nor have I ever done that, and have had no adverse effects in over 50 years of driving Model A’s.[/QUOTE]
X2

dj · 05-13-2021, 01:34 PM

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when you start the car you retard the spark and when you shut it down
Starts better and has a better chance of not back firing , it slows the engine ideal down
so it shuts down quicker .
learned it from the mafca teck director years ago. not saying you have to but good idea.
Dennis

05-12-2021, 09:33 AM	#1
Ed in Maine Senior Member Join Date: May 2010 Location: Washington Cty., ME or Flagler Cty., FL Posts: 1,106	31 Model A Backfires on Shutdown What makes a Model A backfire when you turn the key off? Car seems to run OK otherwise. Ed

05-12-2021, 12:38 PM	#2
nkaminar Senior Member Join Date: Jan 2012 Location: Western North Carolina Posts: 3,897	Re: 31 Model A Backfires on Shutdown Unburnt fuel/air igniting in the hot exhaust manifold, exhaust pipe? There are couple things to try: Let it idle to for a while before turning it off or turn off the fuel and let the carburetor run dry before shutting it off. You can also try pulling the choke to kill the engine then turn it off. Another thing to do, which Model T guys do, is to set the idle so low that the engine dies when the throttle is shut then use the hand throttle to set the idle up enough so that it does not stall when using the car. The advantage with this option is that when descending a hill you can turn the idle down to the point where no fuel/air in getting into the engine. If it is backfiring through the carburetor then that is a different story and probably due to a leaky intake valve. __________________ A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past.

05-12-2021, 03:22 PM	#3
dj Senior Member Join Date: May 2010 Posts: 364	Re: 31 Model A Backfires on Shutdown always make sure you retard the spark before shutting down DEnnis

05-13-2021, 10:55 AM	#4
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,906	Re: 31 Model A Backfires on Shutdown Dennis, Where did you hear that? I have never heard that advice, nor have I ever done that, and have had no adverse effects in over 50 years of driving Model A’s. __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole. Last edited by 700rpm; 05-13-2021 at 01:24 PM.

05-13-2021, 11:46 AM	#5
McMimmcs Senior Member Join Date: Sep 2019 Location: Fort Gratiot, Michigan Posts: 2,296	Re: 31 Model A Backfires on Shutdown [QUOTE=700rpm;2016152]Where did you hear that? I have never heard that advice, nor have I ever done that, and have had no adverse effects in over 50 years of driving Model A’s.[/QUOTE] X2

05-13-2021, 01:34 PM	#6
dj Senior Member Join Date: May 2010 Posts: 364	Re: 31 Model A Backfires on Shutdown Sponsored Links (Register now to hide all advertisements) when you start the car you retard the spark and when you shut it down Starts better and has a better chance of not back firing , it slows the engine ideal down so it shuts down quicker . learned it from the mafca teck director years ago. not saying you have to but good idea. Dennis