The Ford Barn

Model A Man · 11-03-2012, 04:54 PM

what would be or could be the cause of a model A to back fire when letting off the gas? Thanks

700rpm · 11-03-2012, 05:05 PM

Might be the carb is running too lean. Does it do this if you open up the GAV 1/2 turn or more?

Gary WA · 11-03-2012, 05:38 PM

Is it after it's been running for a long period of time?condenser?Also check the points for proper setting.

30ccpickup · 11-03-2012, 05:51 PM

Intake vacuum leak.

steve s · 11-03-2012, 07:03 PM

Are you referring to when you are going down the road or when you are shifting gears or coasting down a hill in gear?

Generally, backfiring under no or light load is due to too-lean mixture to support combustion, so unburned fuel is swept out and accumulates in exhaust system. Either too little fuel (open GAV, raise carb float level, check carb jets) or too much air (as in vacuum leak suggested by 30ccpickup).

Steve

RichPA · 11-03-2012, 07:24 PM

Sponsored Links (Register now to hide all advertisements)

Possible exhaust leak up by the engine

11-03-2012, 04:54 PM	#1
Model A Man Senior Member Join Date: May 2010 Location: Sarasota Florida Posts: 604	cause of back fire what would be or could be the cause of a model A to back fire when letting off the gas? Thanks

11-03-2012, 05:05 PM	#2
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,906	Re: cause of back fire Might be the carb is running too lean. Does it do this if you open up the GAV 1/2 turn or more? __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

11-03-2012, 05:38 PM	#3
Gary WA Senior Member Join Date: May 2010 Location: Clinton,WA/Whidbey Island Posts: 4,104	Re: cause of back fire Is it after it's been running for a long period of time?condenser?Also check the points for proper setting. __________________ www.whidbeymodelaclub.com

11-03-2012, 05:51 PM	#4
30ccpickup Senior Member Join Date: May 2010 Location: Wakarusa, IN Posts: 928	Re: cause of back fire Intake vacuum leak. __________________ http://MODELABASICS.com/ How Things Work on a Model "A" Ford Fordbarners, Feel free to use the pictures on my site to answer questions and create tutorials/tech articles.

11-03-2012, 07:03 PM	#5
steve s Senior Member Join Date: May 2010 Location: Kalamazoo Posts: 1,656	Re: cause of back fire Are you referring to when you are going down the road or when you are shifting gears or coasting down a hill in gear? Generally, backfiring under no or light load is due to too-lean mixture to support combustion, so unburned fuel is swept out and accumulates in exhaust system. Either too little fuel (open GAV, raise carb float level, check carb jets) or too much air (as in vacuum leak suggested by 30ccpickup). Steve

11-03-2012, 07:24 PM	#6
RichPA Senior Member Join Date: Sep 2010 Location: rowland PA Posts: 186	Re: cause of back fire Sponsored Links (Register now to hide all advertisements) Possible exhaust leak up by the engine