Afterfire problem
Thread Starter
Instructor
Joined: Nov 2013
Posts: 249
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From: Piedmont Missouri
Afterfire problem
I am getting huge afterfire in my 69 350/350. Went to check timing and check under distributor cap and found the red wire broken on the ignitor. Will this cause afterfire? Or would the car even run with this wire broken? Maybe it was just hanging on by a thread when I took the cap off.
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From: New Or-leens Loo-z-anna
Beats me...but it can't be a good thing broken like that! I think that you are referring to "Dieseling" when you say "afterfire".....
when the engine tries to keep running even after the ignition is turned off & the key is removed from the switch.
Let us know what you find out.
when the engine tries to keep running even after the ignition is turned off & the key is removed from the switch.
Let us know what you find out.
Thread Starter
Instructor
Joined: Nov 2013
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From: Piedmont Missouri
No, I mean backfiring through the exhaust. I was told "backfiring" only occurs through the carb and when it's through the exhaust it's called "afterfire". Anyway, it sounds like a 12 ga shotgun!
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From: New Or-leens Loo-z-anna
Yes.....loose or shorted distributor wires/timing that is "off" will cause exhaust backfiring like you described.
I "lost" a muffler one time because of it....my rectangular muffler became nearly round----LOL--- when unburned fuel ignited in the muffler after the broken wire moved and made a good connection again.
I "lost" a muffler one time because of it....my rectangular muffler became nearly round----LOL--- when unburned fuel ignited in the muffler after the broken wire moved and made a good connection again.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Afterfire is most commonly caused by a lean condition. If you have a stock-jetted carb on an engine with headers or other modifications to improve airflow, the engine will run lean. This lean condition will cause occasional lean misfire upon closing the throttle plates (deceleration), and you will pump the occasional unburned air/fuel charge right into the exhaust where it will then explode. Once you verify or repair your ignition issues, if the problem persists, richen up the carb.
Lars
Lars
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If it does it after you turn the key off its un burnt fuel in the exhaust. This can be caused by bad ignition or rich condition.
The extra fuel in the exhaust gets very hot and when you shut the car off it let's oxygen work it's way inside the exhaust and then you get an explosion (after fire)
Change out your ignition.
The extra fuel in the exhaust gets very hot and when you shut the car off it let's oxygen work it's way inside the exhaust and then you get an explosion (after fire)
Change out your ignition.
Melting Slicks
Joined: Jul 2010
Posts: 2,503
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From: McGrady NC
St. Jude Donor '15-'16
On earlier ignitions (points and condenser), a failing condenser or a loose wire to the points can cause the same thing. On HEI, I would assume that any loose connection could cause lots of issues. I would suspect everything from timing to idle speed to failed components to leaky carb to vacuum leaks/lean condition. Without looking at it personally it is difficult to diagnose.
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Thread Starter
Instructor
Joined: Nov 2013
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From: Piedmont Missouri
The explosions happen when the motor is running, not after I turn of the ignition. I ordered a new ignitor. When I install it, I'll update you guys if it fixed the problem. Thanks for your help.
Burning Brakes
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From: ESCONDIDO CA
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Use to shut the old V-Dub off for a couple of seconds then back on...
pretty loud double barreled hoot...
pretty loud double barreled hoot...