The Ford Barn

SGT in Ont. · 06-20-2013, 03:43 PM

My engine has started to backfire when I decelerate coming to a stop sign. I've tried re-setting the points, runs fine when cool, but starts to act up when the engine gets hot. Any suggestions?

msmaron · 06-20-2013, 03:49 PM

have you cleaned the jets in the carb, checked the float level, checked the bowl for sludge, rust and junk...more than likely on of the culprits.

700rpm · 06-20-2013, 03:53 PM

Usually means it's running lean. Vacuum leak or carb jet problems. Where do you run your GAV?

RHD · 06-20-2013, 04:03 PM

Could easily be caused by a leak in the manifold or exhaust clamp altering the gas to air mixture, or as said, just running too lean.

Purdy Swoft · 06-20-2013, 05:17 PM

I agree with an exhaust leak . If driving with the the spark partly retarded, this will also contribute to deceleration backfire.

jkeesey · 06-20-2013, 05:29 PM

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Is it backfiring out the carb or the exhaust? They are 2 completely different problems. If you backfire out the exhaust it is most likely a leak, especially if it is once the engine is hot. The muffler and manifold flex once hot and any imperfection in the sealing of either of them will become worse.

SGT in Ont. · 06-21-2013, 07:32 AM

Quote:

Originally Posted by 700rpm

Usually means it's running lean. Vacuum leak or carb jet problems. Where do you run your GAV?

Driving around town the GAV is about 1/2 turn open down to about 1/4. If I go out on the secondary roads where the speed limit is 50mph I have to open the GAV to about a full turn open so that it has the power to keep up with traffic.

SGT in Ont. · 06-21-2013, 07:34 AM

I will re-check for exhaust leak. Thought I had that all sealed up.

06-20-2013, 03:43 PM	#1
SGT in Ont. Senior Member Join Date: May 2010 Location: Milton, Ontario, Canada Posts: 101	Engine backfires when decelerating My engine has started to backfire when I decelerate coming to a stop sign. I've tried re-setting the points, runs fine when cool, but starts to act up when the engine gets hot. Any suggestions?

06-20-2013, 03:49 PM	#2
msmaron Senior Member Join Date: May 2010 Location: Wauconda, IL Posts: 3,600	Re: Engine backfires when decelerating have you cleaned the jets in the carb, checked the float level, checked the bowl for sludge, rust and junk...more than likely on of the culprits. __________________ Mark Maron Ill., Region MARC & MAFCA MARC JSC Member MAFFI Trustee National Facebook Admin. https://www.facebook.com/groups/MARC.group/ A7191-Sport Coupe 29 Roadster 29-Town Sedan 29-Original Special Coupe

06-20-2013, 03:53 PM	#3
700rpm Senior Member Join Date: May 2010 Location: Portland, Oregon Posts: 5,903	Re: Engine backfires when decelerating Usually means it's running lean. Vacuum leak or carb jet problems. Where do you run your GAV? __________________ Ray Horton, Portland, OR As you go through life, keep your eye on the donut, not the hole.

06-20-2013, 04:03 PM	#4
RHD Senior Member Join Date: Jan 2011 Location: New Zealand Posts: 665	Re: Engine backfires when decelerating Could easily be caused by a leak in the manifold or exhaust clamp altering the gas to air mixture, or as said, just running too lean. __________________ R.H.D. Author of Model 'A' Ford technical manuals. Supplier of good original RHD parts.

06-20-2013, 05:17 PM	#5
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: Engine backfires when decelerating I agree with an exhaust leak . If driving with the the spark partly retarded, this will also contribute to deceleration backfire.

06-20-2013, 05:29 PM	#6
jkeesey Senior Member Join Date: Apr 2011 Location: Glenmoore Pa Posts: 1,644	Re: Engine backfires when decelerating Sponsored Links (Register now to hide all advertisements) Is it backfiring out the carb or the exhaust? They are 2 completely different problems. If you backfire out the exhaust it is most likely a leak, especially if it is once the engine is hot. The muffler and manifold flex once hot and any imperfection in the sealing of either of them will become worse.

06-21-2013, 07:34 AM	#8
SGT in Ont. Senior Member Join Date: May 2010 Location: Milton, Ontario, Canada Posts: 101	Re: Engine backfires when decelerating I will re-check for exhaust leak. Thought I had that all sealed up.