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backfire thru the carb ...solved

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
Ok i have had this happen once in a while and because the bronco sat for the last 4 years with out running i thought that it may have bad gas in it. I have now run both tanks 2x. (12/24) I still have this problem. It runs fine for a while then is feels like its missing and then "foomp" backfires thru the carb. My 302 has new plugs, new painless rewire, and new edelbrock carb, new cap and rotor, wires have very few hours on them, but are at least 8 yrs old I do also run headman heders. I am in FL and I do drive in the beautiful weather we have down here, it only been in the mid 80s +/- this last week so. I do feel that my bronco runs a little hot, I still need to get to the parts store and get a 190* stat.

So i know that i could start with new wires and stat, but what could be the issue? Any help would be apreciated, and thanks in advance for your help.
 
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6daze

Sr. Member
Joined
Feb 6, 2007
Messages
798
It was always a timing issue for me when this happened. Check that first.
 

TBS-POPS

Bronco Guru
Joined
Jun 16, 2007
Messages
1,388
Loc.
valley springs, ca
Water temp wise,,,,,180*.. A couple of things to check on your backfire,,, timing,, make sure the vacume advance is working,, clean out the carb. Edelbrocks are fussy about the least ammount of crap in them...I love mine but when it gets stuff in it, it will make things run really weird...
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
X2 on the timing. While stock setting is about 6 degrees you can usually run more without issue. Id shoot for 10-12 just get as much as you can without the back fire. Another thing that could cause it is that the engine is not fully warmed up and the choke is still not fully opened so when you try to jump on the throttle it back fires.
 

markperry

Bronco Guru
Joined
May 8, 2009
Messages
4,175
I had this problem with back firing. Check your fuel pressure, if the engine is not getting enough fuel it will pop and sputter. I have a transparent fuel filter and noticed the fuel flow was very weak, so I went to Oreilly and bought a new fuel pump and replaced the fuel lines and the problem was solved. I saved some money by bending my own fuel lines, the whole project cost 41.00. Now it runs great again!
 

Steve

Bronco Guru
Joined
May 5, 2003
Messages
2,986
Loc.
Grand Junction, CO
As others have said it's probably a timing issue. It could also be running lean, which is NOT a good thing. Worst case it could be an intake lobe on the cam going flat, but since it's an intermittent thing that's probably not the problem.
 

Amac70

ME
Joined
Mar 27, 2002
Messages
3,269
One other thing to check is firing order if you have 2 wires switched it will still run but it will back fire through the carb to.
 

broncomitch

Bronco Guru
Joined
Jan 17, 2008
Messages
2,384
Loc.
west jordan, utah
your carb could not be sealed properly with the manifold, could very well be timing. dose it happen when it gets hotter? check your points. they go bad easy.

might want to clean the carb. (never know how dirty those tanks where) could be you have a bad valve to.
or a simple gaskit leak. start with timing and go from there.

also look at your plug wires, see if there close or touching a exhaust manifold or getting hot when its running. could be arching on the motor causing it to miss fire or not get enough spark.
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
X2 on the timing. While stock setting is about 6 degrees you can usually run more without issue. Id shoot for 10-12 just get as much as you can without the back fire. Another thing that could cause it is that the engine is not fully warmed up and the choke is still not fully opened so when you try to jump on the throttle it back fires.
...

this usally only happens when warm mand have been driving a while
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
I had this problem with back firing. Check your fuel pressure, if the engine is not getting enough fuel it will pop and sputter. I have a transparent fuel filter and noticed the fuel flow was very weak, so I went to Oreilly and bought a new fuel pump and replaced the fuel lines and the problem was solved. I saved some money by bending my own fuel lines, the whole project cost 41.00. Now it runs great again!

That was the other thing that was new... the fuel pump and filter... but the carb was an out of box instal so i may be running lean...
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
After it goes foomp! does it die or does it keep running? Is this at idle or cruising? What kind of ignition set-up?

keeps on running thank God! im am usally running at 45-60 on the coast back and forth to my parents or to my inlaws house. At idle you can here a little mis. My ingition is a "SELECT" not sure who makes it... My coil is an excell.
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
dose it happen when it gets hotter? yes
check your points. they go bad easy. -- they are new...could they go that quick they are only a month old

might want to clean the carb.... will do this.

getting hot when its running... im runningn headers they are hot...

could be arching on the motor causing it to miss fire or not get enough spark.../ they do cross eachother in a few places...
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
While looking at my ingition i saw that my fuel filter is actually right above the manifold. could i be baking my fuel before it gets in the carb?
 

broncomitch

Bronco Guru
Joined
Jan 17, 2008
Messages
2,384
Loc.
west jordan, utah
that happened to me!!! i had a heat wrap on my starter and wrapped a small piece i cut off around my fuel filter. it back fired and got vapor lock allot and was very hard to start.. has not happened sense.

no points dont go out that fast unless they fall apart.

my wires cross each other but never Ark against each other..im worried that there might be a small crack on one of the wires thats causing it..but it would happen all the time if that was the case too.. dont think your headers would cause it to get hot along the wire...they will get hot around the boot but shouldn't on the rest of the wire.

could be a combo of hot gas and a dirty carb..

keep us updated
 

Pa PITT

Contributor
Bronco Guru
Joined
Jul 15, 2005
Messages
11,252
Loc.
Stephenville TEXAS
OLD time way is to raise the hood after dark and watch it run for a while ..Wiggle all the wires around and look for a spark in the dark..
....You can spray carb cleaner around your carb and intake gaskets looking for a vacumn leak if Idle changes then you've found a leak ..WD40 and starter fluid will work also ..But don't blow yourself up if you use either..
....Mine backfired about once a day for 2 months I finally swap in a rebuilt dist ..only cost about $40.00..I never found the real problem but mine was some where in the dis.area.
...After the Dist.change mine ran for a year with out a backfire.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Points can go bad quick usually if the condensor is bad or they are really cheap points. Papitt has a good point about the dist. The bushings could be worn or the advance plate could be gummed up and stick now and then. If replacing the dist you might as well upgrade to electronic the factory dura spark setup is extrememly reliable and easy to get parts for ask for 76 up dist and get a module that has the blue plastic strip.
Good time to upgrade your plug wires too. The ford motorsports wires are about the cheapest aftermarket wire and they are very good I've had mine on for about 10 years and they still look like new.
 
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robinsoncc

Full Member
Joined
Mar 31, 2007
Messages
195
Check for a vacuum leak by spraying carb. cleaning around the connections and intake manifold. Pretty much anywhere the manifold joins to the engine block.
If the rpms go up while spraying than you have a vacuum leak.
 
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Ethansdad73

Ethansdad73

Bronco Guru
Joined
Apr 8, 2008
Messages
1,630
ok, i am going to rip my distributor off and smash it on the gound..... ok not really but i want to. I have tried 6-12* of timing and i cant get it run right. Either it misses or the idle is too low and when i adjust the idle it hesitates on acceleration. I thought i had it but when i hit about 3000 on the tach it misses. I had a bronco buddy of mine tells me that the engine is not origional so it may have a different timing than stock 73 bronco...?


I have changed the thermastat to a 160*, it a little cool but i have headers and they throw a lot of heat. If it idles to long it hits about 210* and then it stalls out possiblly due to vaper lock?


any help would be great...


my frustration may be due to the day that i have had, and i wanted to go for a nice drive and relax.....
 
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