backfire/stalling
 

just bought another Model A and having learning curve issues compared to the one I used to have. This one starts and runs pretty good but was constantly stalling when I came to a stop. Decided to start with tune-up/ timing and plugs and now I have an occasional backfire as well when I let off gas and it still idles down to a stall.. Retime and try again or might it be carb issue as well? Any positive ideas would help!

Re: backfire/stalling
 

Check fuel float level in the carb; probably too high. Make it 1" to the float seam on inverted upper carb body. Add washer gaskets on the float needle valve to lower fuel level.

As a quick test, close the GAV and see if it improves.

Re: backfire/stalling
 

Possibly the butterfly closing to much, it would be like putting your hand over the intake at high throttle when u let off the gas causing a gulp of fuel/backfire , it would also explain dying at idle/starving it. Just an idea to look at and check.


Looking for the front bumper emblem that has "Ford, Made In Canada"

Re: backfire/stalling
 

Thanks for ideas. Watched a Les Andrews video and he reminded me that I forgot to check travel of spark lever. Adjusted steering column so it could retard all the way, reset timing and runs alot better. Still not 100% okay with carb but will roadtest on a warm day first. TBC!:

Re: backfire/stalling
 

Check for wear in the shaft for the butterfly.
Also check the intake and exhaust for leaks.

Re: backfire/stalling
 

funny you should mention the butterfly as I noticed today that it seems rather wobbly and worn out. Thanks for the help!

Re: backfire/stalling
 

not funny, but glad you noticed it.
bob

Re: backfire/stalling
 

What butterfly are we talking about? The choke plate or the throttle plate ??
I'm sure Bob means the throttle plate but is alarot looking at the same one?

Re: backfire/stalling
 

Yes I meant the throttle plate is wobbly. Good thing I gave an extra carb to the guy I sold my last one to!

Re: backfire/stalling
 

It's easy to install an oversize throttle shaft,, the suppliers sell them

Re: backfire/stalling
 

throttle.

Re: backfire/stalling
 

My car stalled when stopping.. Bad gas cap... Get the Eaton style... As for backfiring, kind of sound your GAV might be set too lean, try to open it up to see if that makes and difference.

Re: backfire/stalling
 

One thing you should consider is a possible vacuum leak in the intake/exhaust manifold gasket. There's an interesting article on this subject in the latest issue of the "Restorer" magazine published by the MAFCA.
Rog

Re: backfire/stalling
 

I have a similar problem. I tried another carby but same issue. My backfire develops after about 10-15 minutes of driving. Prior to that it just tends to die when coming to a stop.

Re: backfire/stalling
 

Your backfire problem sounds like it may be a fuel delivery issue. Check for a good long flow of fuel and a good working vent in the gas cap.

The stalling upon decel is usually a float level setting issue. I've set a fair number of floats over the years and never had a problem so I don't know what else to say about that.

Re: backfire/stalling
 

Thanks for the ideas. I will try and get to the bottom of it this weekend.

Re: backfire/stalling
 

I agree check float hieghts

Re: backfire/stalling
 

I think you have a timing issue. Check it very closely and carefully before you tear anything apart.

Re: backfire/stalling
 

I have eliminated an exhaust leak as the backfire cause. I also reset the timing and checked the carby. When adjusting the idle mixture I could wind it all the way in without affecting the idle. The backfire developed again after about 10 minutes and it also stalled after revving the motor and returning to idle. Could this be too lean an idle mixture or incorrect idle jet or too lean in general? If I open the GAV from 1/4 to 1/2 turn the backfire changes and becomes less pronounced.

Re: backfire/stalling
 

"I could wind it all the way in without affecting the idle."

Makes me suspect a vacuum leak - Check at carb mounting flange and intake manifold. With engine idling, spray starting fluid at each junction - If idle speed increases, you've found the problem.