Backfire

Dbbc

Dbbc

Senior Member
Aloha,
just came back from my Sunday drive, and the car is backfiring quite a bit. And the further I advance the spark the louder the backfiring is. Great to see pedestrian jump, but would like the car to run smoothly. This my first Model A and not quite sure what to do. I also have th GAV turn at least an half to 3/4 turn or the car stalls.
The backfiring happens also when I am going down hill when releasing the accelarator.
As always any help would be greatly appreciated.
Mahalo
 
Could be lean mixture, intake leak, exhaust leak a hole in the muffler will also make it backfire. Maybe clogged jet Just some possible causes... good luck
 
Last edited:
I would first check the timing,if the car has not been driven in a while it might be a stuck exhaust valve,or maybe a bad condenser.
 
Lean mixture creates the backfiring? Should I enrich the mixture by adjusting the carburetor?
 
You're already where you should be on the gav, so the lean mixture is probably caused from an intake leak. Or an exhaust leak , sucking air in and igniting on deacceleration, which isn't a lean mixture problem. HAve you pulled your plugs to see how they look? They can provide some good information.
 
I had a very similar problem with my 31 Slant Town Sedan going on a club tour. Turns out it was debris (dirt, not rust) in the carburetor from a tank of contaminated gasoline. Ended up removing the jets, cleaned and blew everything out with compressed air, then my car ran fine.
 
Hi Dbbc, Lean mixture. Your car stalls when you close the GAV, so that is the giveaway. I think your problem is as Country Squire describes above. Happy Motoring!
 
I had the same problem going down a steep hill today in 2nd gear. The problem eased after shifting to 3rd. How do you check for an exhaust leak?
 
Aloha,
Thanks for all the info. It could very well be the exhaust. I removed the manifold in order to paint the block. I should probably have replace the gasket, but I did not have one on hand.
Will try that first and clean the jets.
mahalo
 
fordfun said:
I had the same problem going down a steep hill today in 2nd gear. The problem eased after shifting to 3rd. How do you check for an exhaust leak?
Click to expand...

exhaust leak is easy to find . start car with cold engine and feel around
the manifold . you will feel the leaking air.
 
lean. clean carb. open GAV as much as you need to make it run, every carb is different

the crapahol gas they sell now does bad things to a carb/tank. Do not fill tank unless going on a tour. Keep tank no more than 1/2 full, and drive as much as you can so gas doesn't go stale.

We sure didn't have this problem in the '50s....gas was real gas! Unpolluted fuel!
 
I am having the same problem but my 31 just died after the backfire.
Here's what happned .
I just bought the car ,it is ( or was) turn key ready.
Brought it back from PA, drove it around the hood twice with no problems.
I know how to drive a standard but got my model a start up and shifting education from youtube .

Now the last time I took it out again, very close to home just to get the oil hot enough to dump, I noticed it was almost stalling every time I came to a stop .
So I pulled off the main drag , adjusted the choke /carb jetting knob a bit to try to get it to run leaner or as I hoped to stop it from hesitating at a stop.

Well that was a mistake because I then pulled back out onto the main drag and went about ten feet ,it backfired ,drove " rough" for about another ten feet and then died.
I managed to pull into a side street and had to have it towed the two blocks from my house.
Before I had it towed ,I tried to restart it , it would just crank ,but not turn over and there seems to be a smell of gas so I checked and there was in fact a good amount of excess gas , I assumed that I flooded it ,so I waited a while tried it again and had no luck.
A few days later I went out to the garage and tried again but same thing cranking but no turning over,I made sure the choke/jetting knob was "turned " all the way down , still no go.
I have since ordered a set of points and condenser that are on their way.
This Sunday is my first Model a club meeting and I am hoping someone will help me out and get it running again.
I am sure it must be something small as it was running like a sewing machine before this happned.
Does anyone here have any idea what might have happned and or what might be the problem ?
Thanks in advance ,Frank

P.S. I also changed the plugs figuring they were fouled and they were in fact black with soot but still no go and now no matter were I "set" the choke jetting knob still nothing.
 
Last edited:
tbirdtbird said:
lean. clean carb. open GAV as much as you need to make it run, every carb is different

the crapahol gas they sell now does bad things to a carb/tank. Do not fill tank unless going on a tour. Keep tank no more than 1/2 full, and drive as much as you can so gas doesn't go stale.

We sure didn't have this problem in the '50s....gas was real gas! Unpolluted fuel!
Click to expand...

Depending on the temperature and humidity that can be a bad habit. The more room there is in the tank, the more room for condensation. I have had do thaw out many a frozen fuel line for this very problem. The solution besides keeping it full, Fuel antfreeze, which is alcohol :p
 
Mike V. Florida said:
Timing, the rubbing block will wear closing the points.
Click to expand...

As the rubbing block on the ignition points wear they close up from the original setting, 018-022. This changes the timing. Reset the points to where you originally had them set and it will restore the timing to where you originally had it set.

Tom Endy
 
go ahead and fill it and let it sit and be ready for the consequences. The condensation concept is overrated and implies there is air moving in and out of the tank. I have never had water in fuel from 'condensation'. If there is water in there then the fuel came with water
 
I never have a problem with filling up the tank. Even if it takes several months to run it out. If it's going to be 3 or more months to run it out, then I'll add stabil. Never have a problem. Same with my mower gas. Stabil, and it lasts for 6 months. Did the same to my sons bike all winter. Started right up 6 months later when he came to get it.
 
You must log in or register to reply here.
Back
Top