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What is a Backfire? definition needed

D

DMartin9N-2N

Member
Every now and then someone will post a description of what his tractor is doing, and will say "it backfires" and continue describing his problem. I suspect the term "backfire" is used for different things by different people. How can you help him if he doesn't know the names of things he is talking about??? Backfire might mean engine "popped back" through carburetor when starting, or maybe explosion in muffler?? Different causes! I am a long-time amateur fix-it person, I like to keep old stuff running. I read the forums for a sort of entertainment. BTW, folks on an antique Mopar site I follow also use casual words to describe technical problems.

Dennis in W. Tennessee
 
It is when unburned fuel ignites and creates "explosion" or backfire, usually caused by misfires.

One of the 9000 HP engines at a site I do work at backfired, blew the muffler apart and the windows out of the nearby building.
 
unburnt fuel exploding in a hot exhaust pipe. Not uncommon in older machines with low compression causing incomplete combustion and the passing of gasoline into the exhaust system.
 
I have an old 2 cycle golf cart that will do that occasionally on a down hill run. Happens so rarely it scares the daylights out of me every time. Neighbors dog was chasing it one day when it backfired, and I didn't see her for 2 days afterward. Just wish I could figure a way to make it backfire when I want it too.
 
Would the type of fuel matter? I was told to use leaded fuel and mix half a quart of ATF fluid with it. I haven't seem to ever have any problems.

I'm new to this forum, just bought a 42 9N but have used an 8N WHEN I WAS A KID.
 
Well I know the secret to backfiring on demand,turn the key off while rolling(coasting in gear), keep the throttle full on. When you turn the key back on, it will backfire,on a car it will blow the muffler off after repeating several times. It was a good way to scare dogs and small children.:)
 
Well technically a backfire happens in the intake side of the engine. If it happens in the exhaust side its called an afterfire. But afterfire sounds so stupid nobody uses it.
 
Using leaded fuel is actually bad for an engine. I have run my antique car for years on unleaded with no problems. Back in the old days, when most gasoline was leaded, I was doing a fair amount of heavy engine work. One of the things I noted was that the exhaust valves in particular were prone to burning. They were usually also caked up with lead deposits. This was back in the late 1960s into the early 1970s. Some years later, after unleaded fuels became the normal fuels, there was a notable change in the inside of engines. One thing that I noted was that burned valves and valve jobs became much less common. I also noted that the inside of engines was a lot cleaner. There were no longer pockets of accumulated lead residues found throughout the engine.
My opinion is that removal of lead from our fuels was a good thing. The only possible thing that you may need to do in the future would be to install harder exhaust valves.
 
Ok.... I re-read my original post and feel like an idiot! I meant ethanol free gas! I have was doing a bunch of reading and had leaded fuel on my brain which translated into my post

So, I meant to say ETHANOL FREE GAS with 1/2 at of ATF fluid.

Sorry for the mix up and the confusion...
 
That is what happened on the 9000 HP, ignition went off, natural gas did not stop, ignition came on and blew muffler apart. The mufflers are 4-5 feet in diameter and 20 feet long, so big bang.
 
(quoted from post at 23:34:54 12/30/16) Would the type of fuel matter? I was told to use leaded fuel and mix half a quart of ATF fluid with it. I haven't seem to ever have any problems.

I'm new to this forum, just bought a 42 9N but have used an 8N WHEN I WAS A KID.
Click to expand...
More likely they meant use alcohol free fuel with ATF.
The ATF helps free up rings and valves if sticking.
Not needed all the time but it does help sometimes.

BTW, a 194"2" would be a "2"N.
9N started in 193"9", 2N in 194"2" and the 8N in 194"8".
The serial number on a 2N would still start with 9N though.
Check out [b:3c58990d78]John Smith's[/b:3c58990d78] excellent site for more info.
 
I had a bus that started backfiring on the exhaust side. It did it a couple of times and I was just beginning to get concerned when it did it and blew the exhaust manifold to smithereens on one side. It got really loud, really fast. Luckily I had just left the bus lot. That was only a 429 gas engine, too!

Funny story - my favorite bus of all time had a 370 gas engine. One of those things where you just feel like you are just right "at one" with the machine each time you turn the key. I had an evening trip in the winter. I was on my layover and would start the bus periodically to keep it warmed up and run it long enough to heat it up inside. I had walked the isle to check behind the bus and decided to start it. I just reached down and hit the key and pumped the gas once with my right foot. I kind of had to stand back a ways as it was a 4 speed.

Well, it didn't start. So I sat down and fired it up but it would only idle which was very odd. I let it run for about 15 seconds but it just seemed to be choking out. That's when it hit me that something was wrong. I threw open the door and lifted the hood and put my hand on the air breather - it was hot as a firecracker. I took the wing nut off quick and made my plan. I knew when I lifted that lid the filter fire would get oxygen. Unfortunately, no part of my plan involved getting my winter gloves. I lifted the lid and the filter burst into flames. I grabbed it and threw it out into the snow in front of the bus. No lie, it was like a bonfire about four foot tall. I was in downtown Kansas City by the coffee roasterie. I just knew someone in one if those lofts was going to call the fire department. About that time my trip calls, so I put the breather top back on and drove the rest of the night with no air filter. I learned two things - too much fuel without enough starter action can cause even the best bus to backfire just enough to light the filter on fire, and waffle marks burned into your palms take months to heal.

Amazingly, sucking in that super heated air didn't do any lasting damage. It ran a little different for a while, but there was A LOT of soot down the two barrel carb. I was mad because you could have eaten off that carb before and now the throats looked like a campfire hotdog. It looked that way until the day I sold that bus. I never did start it again without sitting down and revving it good to make sure nothing was ablaze.
 
Yep seen and had more then one muffler become a bomb under a car or truck and some times when they go off they damage more then just the muffler. Or what is even neater is setting up a extra spark plug in the exhaust system so as to make a flame thrower exhaust
 
I have yet to find any engine damage due to unleaded gas in any thing. Be it an old tractor or an old motorcycle or old car or truck and I have many of them. .
 
Unleaded gas work just fine in any thing you own be it new or an engine made in the 40s. Ever since unleaded gas came out in the 70s I have run it in every thing I own and have owned and have yet to find any damaged cause by it. And when I say any thing I mean tractors lawn mowers motorcycles car and truck. And yes I have both newer and older of them all.

Now as for ATF I do at time run a quart of it in 3 gal of gas to clean carbon out and to free up sticking valves and rings.

I also use ATF to free up locked up engines that have locked up due to sitting a long time with out being turned over
 
Going off topic and then learned by doing so is a good thing not bad.

I tel many people information and knowledge is something that should be shared not something not to be freely given.

I also believe any day a man can learn something new is a good day for that man
 
I thought the 2Ns came with the magneto starters. Mine has
no spot for the engine crank and the choke is at the steering
wheel. Not the front of the tractor.

I also tried to look up my serial number (I believe it was on this
site) and mine fell in the 9N numerics. I wonder if my tractor
was an early 42 model built in 41?
 
There are many sites online that will tell you what kind of damage does occur to older engines prior to hardened valve seats. The only people I know who make claims that ethanol laced gas not causing any damage are either tree hugging whack jobs or corn growers who want people to use ethanol laced gas in spite of potential problems for their own personal gain. The lead in gas reduced the transfer of metal between the cast iron head/valve seat and the steel valve. You can look that up.

Now you take an older engine, replace any rubber parts in the fuel system with parts made of modern materials, take the head/s in and have hardened seats installed and yea, you can burn ethanol laced gas. Keeping this tractor related IIRC the Ford 8N had hardened seats from the factory.

Also tell me why small engine manufactures just a year or 2 ago were telling buyers to run ethanol free gas? Why do all the marine and small engine mechanics (who don't sell gas) tell their customers not to use ethanol! I wish MN would repeal the law requiring ethanol in newer vehicles. When I went to IL in Oct our Suburban picked up about 1.5 MPG when I was in states that allowed using E zero gas. Kinda makes one mad when they are burning more fuel because of ethanol!

Rick
 
"I thought the 2Ns came with the magneto starters."

There are a lot of misconceptions about the 2N.
Actually, about all of the N tractors. Check out John's site.
 
http://just 8n's/Identifying-Your-Ford-Tractor.html

I reckon you're right. This is the site I looked up my serial
number on. Mine shows to be a 2N. Thanks for the correction.
 
I have a grain truck that has the 429 in it, I have to pull a hill over the Wisconsin river to get to a gas station while loaded, when I pull into the station and shut it off a second or two after shut down it backfires, had more then one person jump like crazy and tell me it about gave them a heart attack.
 
"Thanks for the correction."

Not a correction, just a pointer in the right direction.
You have a new to you tractor that is 65+ years old.
Most of us have been there too.
It will need maintenance, fluids, points, plugs, etc.
You will want to get the manuals for that tractor.
It may also benefit you to visit the 9N/2N/8N forum here on YT.
Here's a link to that as well.
 
I may be a whack job but I'm no tree hugger nor a corn grower and I've never had an ethanol problem with anything I own and I bet there's a few others like me. So put that in your ethanol free pipe and smoke it. TDF
 
Best definition of Backfire can occur hours after eating a large
quantity of ham and beans and you are close to an open fire. You
will see FIRE shooting out your BACKside. Put the two together
and you get BACKFIRE.

So BACKFIRE can also occur when unburned fuel(methane) gets past
the exhaust valve.
 
I was always taught that Backfire is the burning of fuel Back to the carb and air filter. After burn is what burns in the exhaust system and
muffler.
 
(quoted from post at 20:58:25 12/30/16) Well technically a backfire happens in the intake side of the engine. If it happens in the exhaust side its called an afterfire. But afterfire sounds so stupid nobody uses it.
Click to expand...

CORRECT!
 
I run unleaded in the 35 Chevy truck. It has 78,000 miles on it, but was part of the GM engine exchange program about 50,000 miles. So, it doesn't have too many miles and is clean as a whistle inside. I worried about it when the switchover came and I couldn't get leaded anymore, but I don't even think of it now.
 
Ya many people do not understand the lead in gas was an anti-knock additive. So when they switched to unleaded gas they had to do something else to keep anti-knock from being a problem other then just setting timing a bit different. People also tend to forget gas back in the 30s and 40s and even the 50s is not what it was in the 70s or 80s.
 
I'll refute some comments that say small engine manufacturers recommend against using gasoline containing ethanol. My two Stihl chainsaws simply recommend against using gasoline that contains over 10% ethanol. This fall I bought a new Generac backup generator, and the book on it says the same thing, avoid gasoline with over 10% ethanol.

I've used 10% ethanol in everything for years, and I've never had one single problem that I could say was caused by it.
 
(quoted from post at 10:25:25 12/31/16) I'll refute some comments that say small engine manufacturers recommend against using gasoline containing ethanol. My two Stihl chainsaws simply recommend against using gasoline that contains over 10% ethanol. This fall I bought a new Generac backup generator, and the book on it says the same thing, avoid gasoline with over 10% ethanol.

I've used 10% ethanol in everything for years, and I've never had one single problem that I could say was caused by it.
Click to expand...

I bought a new walk behind string trimmer last spring that the owners manuals says no ethanol and several other small engine makers do the same. I also bought a new Zero turn in June. That one says I can run E10. Engine on the trimmer and zero turn are from the came company. Go figure.

Now I think where some of the problems we see it the fact that winter and summer equipment here can sit for 6 months or more before it's needed. Even with stabil we push the limits.

Rick
 
I suffered a backfire or, maybe more correctly, an after-fire, in our Yamaha golf cart this Fall. Soon after, it would not start. Turned out the explosion forced a hose from the crankcase to the fuel pump to come off, thus no fuel to start.

Only ethanol-based issue I have had so far: the fuel reacted poorly with the rubberized carb-mounting boots on my Ski-Doo snowmobile, caused one of them to fail. Fortunately, I caught it soon enough and it was partly in place, allowing sufficient cylinder oiling from the fuel drawn in, that I did not burn the piston up. Two new boots and it ran great! The mechanic said the ethanol effected the aluminum inside the rubber, causing them to split and separate, and let air in after the carb.
 
A true Backfire "explosion" can only happen if there is enoufh air for it to happen. When I experience a Backfire my first thought is why did the mixture have a excessive amount of air available.

Something to think about during the combustion process all the air is consumed but some of the fuel is not so how can the exhaust backfire when the air has been consumed.

That's why my thoughts are never toward a rich condition as the cause of a backfire event.
 
Speaking of mufflers, quite a few years ago when Marilyn and I were dating I was teaching her how to drive a stick shift one Saturday afternoon. The car was a 59 Chevy, she was driving and after some jerking and chugging she finally got it up to cruising speed. I was on the passenger side, bench seat of course and I slid over beside her and reached up and turned off the key, the key was in the dash back then. When the engine died she instinctively pushed down on the foot feet, then I turned the key back on. When the explosion happened I was ready to grab the steering but she kept it under control OK. I was reminded to never do that again though and I obeyed orders. LOL
 
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