The Ford Barn

dynaflash_8 · 08-13-2011, 02:57 AM

So iv been driving the heck outta my 30 coupe. Over 300 miles so far in about 2 weeks. One thing i can not get rid of is the pop out the tailpipe between shifts. It doesnt do it when its cold, but after about 10 miles between shifts it has a loud backfire out the tailpipe. Seems to be worse when its retarded, but if i give it full advance, its not so bad. Also, if i drive the car for long distances, when i go to shut it off, it backfires out the tailpipe like a shotgun.

This backfire occures 10 seconds after everything in the motor has stopped. Tonight it did this and blew the muffler off the car.

Iv done a full tune up, points rotor the whole bit, and tinkered with the carb, and it will not quit. What the heck is going on???

Mike V. Florida · 08-13-2011, 03:21 AM

When my car backfired after turning it off, I readjusted the timing in accordance with the procedure posted by Marco and backfiring went away.

http://abarnyard.com/workshop/timing.htm

Jack '29 Sport Coupe · 08-13-2011, 03:44 AM

You will get a lot of advice on this one, but here are a couple of things to check.

1. Float level. Turn off the gas valve before shutting down and let it run out of
gas before turning off the switch. if it takes too long to stop, it probably means
that the float is too high.

2. Try driving with spark lever in different positions other than all the way up or
all the way down. You mentioned that it's worse when the lever is up. That is
normal, because you shouldn't be driving with it in the up (retarded) position.
I suggest your timing might be off. Each lever has its own "sweet spot" and you
have to find it. Mine likes it all the way down at highway speeds, and about 3/4
down if I am just crawling along at 10-15 mph. Also, don't forget to make sure
the throttle is all the way up when you shut off the engine. Good luck.

Jack

RonC · 08-13-2011, 05:36 AM

You can check your timing by retarding the spark lever, remove the distributor cap and body, turn on the ignition key (make sure your car is in neutral with E-Brake on). Press on the timing pin and slowly crank the engine until the pin sets into the timing gear recess. Do this while watching the points. At the exact moment the timing pin falls into the timing gear recess the points should spark. If not your timing is off. My guess is your timing is late

roccaas · 08-13-2011, 07:37 AM

That shotgun blast 10 seconds after you turn off the engine - bad condenser. Easy and cheap fix.

Do you get popping from the tail pipe when you let off the gas at speed? If so, check your mixture, it is probably a shade too lean.

Frank Nemo · 08-13-2011, 08:27 AM

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When I had the "shotgun blast" after turning off the ignition, I traced the problem to a bad fit between the exhaust manifold and the tailpipe. After tightening that connection I had no more problems.

It does make for an attention grabbing entrance when you arrive at your destination. When I had the Shotgun blast impression, it was time to shout "Shoot him in the pants the coat belongs to me".

joltesvig · 08-13-2011, 08:47 AM

I had a backfire issue until I put a brand-new shiney condenser in there...haven't had the problem since...but I still put my fingers in my ears immediately when I shut her down for at least 10 seconds!

Frank, where does that interesting quote come from you shout?

Frank Nemo · 08-13-2011, 01:07 PM

Frank, where does that interesting quote come from you shout?[/QUOTE]

I had an old buddy who would always say "Shoot em in the pants the coat belongs to me" any time he would hear a gun shot sound or back fire. I have no idea where the quote came from, but now that he has passed I always get a smile on my face when I have the occasion to use it and remember his humor.

08-13-2011, 02:57 AM	#1
dynaflash_8 Member Join Date: Jul 2011 Location: Auburn WA Posts: 73	Why does my Model A backfire between shifts and after its off? So iv been driving the heck outta my 30 coupe. Over 300 miles so far in about 2 weeks. One thing i can not get rid of is the pop out the tailpipe between shifts. It doesnt do it when its cold, but after about 10 miles between shifts it has a loud backfire out the tailpipe. Seems to be worse when its retarded, but if i give it full advance, its not so bad. Also, if i drive the car for long distances, when i go to shut it off, it backfires out the tailpipe like a shotgun. This backfire occures 10 seconds after everything in the motor has stopped. Tonight it did this and blew the muffler off the car. Iv done a full tune up, points rotor the whole bit, and tinkered with the carb, and it will not quit. What the heck is going on???

08-13-2011, 03:21 AM	#2
Mike V. Florida Senior Member Join Date: May 2010 Location: South Florida Posts: 14,054	Re: Why does my Model A backfire between shifts and after its off? When my car backfired after turning it off, I readjusted the timing in accordance with the procedure posted by Marco and backfiring went away. http://abarnyard.com/workshop/timing.htm __________________ What's right about America is that although we have a mess of problems, we have great capacity - intellect and resources - to do some thing about them. - Henry Ford II

08-13-2011, 03:44 AM	#3
Jack '29 Sport Coupe Senior Member Join Date: May 2010 Location: Cincinnati, Ohio Posts: 798	Re: Why does my Model A backfire between shifts and after its off? You will get a lot of advice on this one, but here are a couple of things to check. 1. Float level. Turn off the gas valve before shutting down and let it run out of gas before turning off the switch. if it takes too long to stop, it probably means that the float is too high. 2. Try driving with spark lever in different positions other than all the way up or all the way down. You mentioned that it's worse when the lever is up. That is normal, because you shouldn't be driving with it in the up (retarded) position. I suggest your timing might be off. Each lever has its own "sweet spot" and you have to find it. Mine likes it all the way down at highway speeds, and about 3/4 down if I am just crawling along at 10-15 mph. Also, don't forget to make sure the throttle is all the way up when you shut off the engine. Good luck. Jack __________________ Cincinnati, Ohio

08-13-2011, 05:36 AM	#4
RonC Senior Member Join Date: May 2010 Location: Rhode Island Posts: 1,868	Re: Why does my Model A backfire between shifts and after its off? You can check your timing by retarding the spark lever, remove the distributor cap and body, turn on the ignition key (make sure your car is in neutral with E-Brake on). Press on the timing pin and slowly crank the engine until the pin sets into the timing gear recess. Do this while watching the points. At the exact moment the timing pin falls into the timing gear recess the points should spark. If not your timing is off. My guess is your timing is late

08-13-2011, 07:37 AM	#5
roccaas Senior Member Join Date: May 2010 Location: Savannah, GA Posts: 1,300	Re: Why does my Model A backfire between shifts and after its off? That shotgun blast 10 seconds after you turn off the engine - bad condenser. Easy and cheap fix. Do you get popping from the tail pipe when you let off the gas at speed? If so, check your mixture, it is probably a shade too lean. __________________ 20 years ago we had Johnny Cash, Steve Jobs, and Bob Hope. Now we have no Cash, no Jobs, and no Hope...please don't let Kevin Bacon die!

08-13-2011, 08:27 AM	#6
Frank Nemo Senior Member Join Date: May 2010 Posts: 159	Re: Why does my Model A backfire between shifts and after its off? Sponsored Links (Register now to hide all advertisements) When I had the "shotgun blast" after turning off the ignition, I traced the problem to a bad fit between the exhaust manifold and the tailpipe. After tightening that connection I had no more problems. It does make for an attention grabbing entrance when you arrive at your destination. When I had the Shotgun blast impression, it was time to shout "Shoot him in the pants the coat belongs to me".

08-13-2011, 08:47 AM	#7
joltesvig Senior Member Join Date: May 2011 Location: Carthage, NC Posts: 147	Re: Why does my Model A backfire between shifts and after its off? I had a backfire issue until I put a brand-new shiney condenser in there...haven't had the problem since...but I still put my fingers in my ears immediately when I shut her down for at least 10 seconds! Frank, where does that interesting quote come from you shout? __________________ John the Model A Rookie from North Carolina

08-13-2011, 01:07 PM	#8
Frank Nemo Senior Member Join Date: May 2010 Posts: 159	Re: Why does my Model A backfire between shifts and after its off? Frank, where does that interesting quote come from you shout?[/QUOTE] I had an old buddy who would always say "Shoot em in the pants the coat belongs to me" any time he would hear a gun shot sound or back fire. I have no idea where the quote came from, but now that he has passed I always get a smile on my face when I have the occasion to use it and remember his humor.