Exhaust backfire...causes?
Thread Starter
3rd Gear Member
Joined: Jul 2005
Posts: 566
From: Sugar Land, Texas
Exhaust backfire...causes?
My son returned from his CampJam camp in Houston on Friday and drove the old 67 200ci I6 to and fro. Upon return to the house, the stang was idling very rough. Just thought is was about time to change points and set timing. We checked the plugs and set the gap, changed and set point gap, checked dwell, and did the timing. Still idling rough and dies if not giving it gas. Drove it around the block and it begin to have exhaust backfire when let off of gas.
What gives here? Dwell is fine, timing set, but still wanting to die at idle. What do we check next? Thanx in advance...
Update: Looks like the old 40 year old fuel tank needs replacing. Apparently, alot of rust was clogging up the fuel filters. One before the fuel pump is pictured and had quite a bit in it. The other before the carb was relatively clean. Guess I will start looking for a good deal on a new tank. What effect does the rust have upon the fuel pump and carb? Will the pump clog up as well and will the carb need cleaning/adjusting?
[IMG]local://upfiles/19071/9FF2A8AF8B5543A185B26BB045385610.jpg[/IMG]
What gives here? Dwell is fine, timing set, but still wanting to die at idle. What do we check next? Thanx in advance...
Update: Looks like the old 40 year old fuel tank needs replacing. Apparently, alot of rust was clogging up the fuel filters. One before the fuel pump is pictured and had quite a bit in it. The other before the carb was relatively clean. Guess I will start looking for a good deal on a new tank. What effect does the rust have upon the fuel pump and carb? Will the pump clog up as well and will the carb need cleaning/adjusting?
[IMG]local://upfiles/19071/9FF2A8AF8B5543A185B26BB045385610.jpg[/IMG]
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Joined: Oct 2004
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From:
RE: Exhaust backfire...causes?
Check the fuel system. First to check are the filters. Both the inline and the one on the sending unit in the tank. Is it a new tank of gas? Or the old 3 month old gas? Sounds like water in the fuel. Get a bottle of fuel additive that takes out the water such as "Heet".
Thread Starter
3rd Gear Member
Joined: Jul 2005
Posts: 566
From: Sugar Land, Texas
RE: Exhaust backfire...causes?
Glen...thanx for the quick reply. THis is a daily driver so the fuel is fresh and I just put on two clear inline fuel filters about a month ago. Guess is could be some bad gas or condensation in the tank. Worth trying the Heet... My 1st thought was fuel/carb prob so went to Autozone for a carb rebuild kit... might still do that as well...
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Joined: May 2005
Posts: 2,445
From:
RE: Exhaust backfire...causes?
Back fire through the exhaust is a sign of an overly rich condition. Check the idle mixture screw adjustment. Should be aproximately 1.5 turns CCW, give or take 1/2 turn. If you have to deviate too far from that, especially to the lean side, you could have a float issue or a float seat issue, or a leak through the power valve/accelerator pump section.
If you decide to rebuild the carb, look closely at where the check ***** and the weight are. I've seen some pretty suprising things done to these old carbs to keep them running.
When removing the *****, and weights, Cover the carb body completely, then uncover each hole one by one so you get things back in the correct spot. Different engines had different ***** and weights. Most often the carb kit picture is generic, and not necessarily the one for your exact application. If you follow the wrong picture, it will not run correctly.
Good luck,
If you decide to rebuild the carb, look closely at where the check ***** and the weight are. I've seen some pretty suprising things done to these old carbs to keep them running.
When removing the *****, and weights, Cover the carb body completely, then uncover each hole one by one so you get things back in the correct spot. Different engines had different ***** and weights. Most often the carb kit picture is generic, and not necessarily the one for your exact application. If you follow the wrong picture, it will not run correctly.
Good luck,
Thread Starter
3rd Gear Member
Joined: Jul 2005
Posts: 566
From: Sugar Land, Texas
RE: Exhaust backfire...causes?
Scott...good advice and tips there. We may just attempt that carb rebuild after all. However, will have to convince the wife to let us use the kitchen table as a workbench. 
Way toooo hot and humid out in the garage these days!!!
Way toooo hot and humid out in the garage these days!!!
5th Gear Member
Joined: May 2005
Posts: 2,445
From:
RE: Exhaust backfire...causes?
You would have to have *THE* most understanding and wonderful wife in the world for that to ever happen!
If you rebuild that carburetor on the kitchen table, and don't end up sleeping on the couch for the month it takes to get the gas smell out of the house, you will be the envy of every married man in the modern world.
Good luck!
If you rebuild that carburetor on the kitchen table, and don't end up sleeping on the couch for the month it takes to get the gas smell out of the house, you will be the envy of every married man in the modern world.
Good luck!
Thread Starter
3rd Gear Member
Joined: Jul 2005
Posts: 566
From: Sugar Land, Texas
RE: Exhaust backfire...causes?
ORIGINAL: Scott H.
You would have to have *THE* most understanding and wonderful wife in the world for that to ever happen!
If you rebuild that carburetor on the kitchen table, and don't end up sleeping on the couch for the month it takes to get the gas smell out of the house, you will be the envy of every married man in the modern world.
Good luck!
You would have to have *THE* most understanding and wonderful wife in the world for that to ever happen!
If you rebuild that carburetor on the kitchen table, and don't end up sleeping on the couch for the month it takes to get the gas smell out of the house, you will be the envy of every married man in the modern world.
Good luck!
Yep, I ran the idea past SWMBO. She informed me that the weather would be cooling off really soon, something about "when hell freezes over". I think she is in charge of the weather too.....
I ♥ Acer
Joined: Oct 2004
Posts: 17,565
From:
RE: Exhaust backfire...causes?
ORIGINAL: Cogtx
My son returned from his CampJam camp in Houston on Friday and drove the old 67 200ci I6 to and fro. Upon return to the house, the stang was idling very rough. Just thought is was about time to change points and set timing. We checked the plugs and set the gap, changed and set point gap, checked dwell, and did the timing. Still idling rough and dies if not giving it gas. Drove it around the block and it begin to have exhaust backfire when let off of gas.
What gives here? Dwell is fine, timing set, but still wanting to die at idle. What do we check next? Thanx in advance...
Update: Looks like the old 40 year old fuel tank needs replacing. Apparently, alot of rust was clogging up the fuel filters. One before the fuel pump is pictured and had quite a bit in it. The other before the carb was relatively clean. Guess I will start looking for a good deal on a new tank. What effect does the rust have upon the fuel pump and carb? Will the pump clog up as well and will the carb need cleaning/adjusting?
[IMG]local://upfiles/19071/9FF2A8AF8B5543A185B26BB045385610.jpg[/IMG]
My son returned from his CampJam camp in Houston on Friday and drove the old 67 200ci I6 to and fro. Upon return to the house, the stang was idling very rough. Just thought is was about time to change points and set timing. We checked the plugs and set the gap, changed and set point gap, checked dwell, and did the timing. Still idling rough and dies if not giving it gas. Drove it around the block and it begin to have exhaust backfire when let off of gas.
What gives here? Dwell is fine, timing set, but still wanting to die at idle. What do we check next? Thanx in advance...
Update: Looks like the old 40 year old fuel tank needs replacing. Apparently, alot of rust was clogging up the fuel filters. One before the fuel pump is pictured and had quite a bit in it. The other before the carb was relatively clean. Guess I will start looking for a good deal on a new tank. What effect does the rust have upon the fuel pump and carb? Will the pump clog up as well and will the carb need cleaning/adjusting?
[IMG]local://upfiles/19071/9FF2A8AF8B5543A185B26BB045385610.jpg[/IMG]