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#1 |
Senior Member
Join Date: Jul 2012
Location: Venice, FL
Posts: 667
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A club members model A will start right up but then it backfires and stops running. He has set the timing and changed the condenser and has ordered another coil but doesn't have it yet. He has installed an aluminum intake manifold with new gaskets. Can this be caused by a leaky intake manifold?
Thank for your suggestions, Al |
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#2 |
Senior Member
Join Date: May 2016
Location: Scottsdale, Arizona
Posts: 656
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Good Afternoon...He might want to check the little wire between the lower and upper plate on the distributor...Ernie in Arizona
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#3 |
Senior Member
Join Date: Jun 2010
Posts: 788
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While he waits for new parts good time for 6 volt 'tight & bright' maintenance on all wiring connections.
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#4 |
Senior Member
Join Date: May 2010
Location: Between Seattle & Tacoma
Posts: 2,411
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#5 |
Senior Member
Join Date: Jan 2012
Location: Western North Carolina
Posts: 5,874
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Backfiring can be caused by a number of things. If it happens in the intake then it is usually caused by a lean mixture. If it happens in the exhaust then ignition problems can be the cause.
Besides going through the ignition system, check the fuel flow to the carburetor and check for clogged jets in the carburetor or a clogged float valve. Taking the bolt off the bottom of the carburetor can check the fuel flow from the tank all the way through the carburetor. Do this outside with a fire extinguisher handy.
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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. |
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#6 |
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Join Date: May 2010
Location: Gwynn's Island Va
Posts: 1,605
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#7 |
Senior Member
Join Date: Jul 2012
Location: Venice, FL
Posts: 667
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Thank you all for your suggestions. We are having a tech day today and we'll start off with your suggestions.
Al |
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#8 |
Senior Member
Join Date: Jun 2022
Location: Northern Colorado
Posts: 463
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My monies' on nkaminar, and his lack of fuel flow theory. A while back, I was having the same symptoms, and he suggested a "lean" mixture was the problem. Mine was due to a crap filled gas tank that resulted in a clogged fuel flow filter valve that severely restricted gas getting down to the carb. It would start, backfire and quit.
rkaminar also gave me a wonderful tutorial on the function of the GAV. Priceless! Good luck with yours. |
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#9 | |
Senior Member
Join Date: Feb 2011
Location: Lincoln, Nebraska
Posts: 2,011
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Dave / Lincoln Nebraska |
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#10 |
Senior Member
Join Date: Mar 2013
Location: Blue Springs, Missouri
Posts: 218
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Hi, my 28 Leatherback has just started backfiring through the exhaust after runing great, here is a rundown I have tried to fix the 28,
1. drained and refilled the gas tank in case of bad fuel. 2. distributer points not grounded 3. distributor housing grounde4. 4. points set correctly 5. checked timing. 6. new intake and exhaust gasket and glands 7. manifolds torqued to 40 lbs 8. tried 2 additional carbs 9. compression tests; dry wet cyl 1 54 60 cyl 2 53 60 cyl 3 54 60 cyl 4 60 60 with all this it still backfires, if I advance the spark it quiets down |
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#11 |
Senior Member
Join Date: Feb 2011
Location: NNNNNNNNJJJJJJJJJJ
Posts: 7,651
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sticky valve?
add MMO to your gas |
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#12 |
Senior Member
Join Date: Jul 2010
Location: Pennsylvania
Posts: 1,251
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Another cause of leaning out that can cause backfires and stalling is a clogged vent in the gas tank cap. A bad vent causes a partial vacuum in the gas tank as the fuel flows to the carb, which causes the flow to slow or stop.
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#13 |
Senior Member
Join Date: Jan 2019
Location: Florida Panhandle
Posts: 626
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Might also check the valve lash.
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#14 |
Senior Member
Join Date: Mar 2013
Location: Blue Springs, Missouri
Posts: 218
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Thanks guys, I'll try anything at this point
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#15 |
Member
Join Date: Sep 2016
Location: San Jose, CA
Posts: 54
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Are bushings around throttle plate shaft worn? Are needle valve seats in carb in good shape? Basically; does your carburetor need rebuilding?
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#16 |
Senior Member
Join Date: Mar 2013
Location: Blue Springs, Missouri
Posts: 218
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I have 3 carbs I rebuilt with new everything and I've tried all 3. Thank you.
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#17 | |
Senior Member
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,716
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![]() Quote:
It sounde like your problem is in the distributor
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#18 |
Senior Member
Join Date: Mar 2013
Location: Blue Springs, Missouri
Posts: 218
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That's what i'm thinking, but everything checks out with the distributers. I have 3 and none seem to correct the problem. Right now I'm completely stumped.
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#19 |
Senior Member
Join Date: May 2012
Location: Chillicothe, Missouri
Posts: 1,684
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I wonder if you have internal cross-fire in the distributor cap???
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#20 | |
Senior Member
Join Date: Jun 2015
Location: Red Deer, Alberta
Posts: 5,716
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Is there a vacuum port on the intake manifold? Possible vacuum leak?
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