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Old 05-26-2021, 10:25 PM   #1
mgambuzza
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Default Carb backfire when release accelerator - Part 2

Now that almost all the ignition pieces were replaced, and still intermittently having acceleration issues, I wanted to look at a potential fuel issue. Ordered the Zenith strainer, bulb filter, gaskets, gas valve, and valve filter. The first good news was while the valve was off, and I removed the strainer, fuel didn't pour out giving me the first indication that it was functioning - but it was filthy. Placing it up to a light and I couldn't see through it, so it was a worthwhile replacement. Then the golden (glass) bulb that seemed murky. Came off with little effort, the screen looked different from the one I received from the vendor (picture included) and there was a solid 1/4 - 1/3" sediment on the bottom. Cleaned out the bowl with sediment, removed the old gasket, placed new gasket, along with screen, and turned on the fuel. Bowl filled immediately crystal clear with no particles, and no leaks at the bowl or strainer - hopefully a partial indication that there isn't an issue in the tank. Fired up and ran for 5 minutes and no leaks - success for tonight and can't wait to try tomorrow (it was raining tonight).



I wasn't sure whether the full round screen on the bowl did more damage than good as I can see where if there was sediment it would hit the full screen and divert it up to the feed to the carburetor, leaving the strainer to do all the filtering(even though there was a lot of sediment on the bottom). With the hole in the screen I can see where the sediment will go into the bowl first, and the more "filtered" gas will go to the carb. Will let you all know how this improvement affects the operation. With Memorial Day coming, and I have an invite to drive some vets in the parade, I hope these couple fixes make me good to go.
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Old 05-27-2021, 09:49 AM   #2
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Default Re: Carb backfire when release accelerator - Part 2

So far so good! Did a 26 mile drive this morning, big uphills, downhills, curvy roads, city, and country driving and no stumbling or hesitation like I was experiencing. I won't deny the fact my 91 year old car probably still will have some rust in the tank whose particles may affect an clog filters, etc. Since I'm the new owner of this, I'll be much more aware of this, ensure filters/gaskets are replaced, and MMO in the gas to help with the rust issues.
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Old 05-27-2021, 12:19 PM   #3
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Default Re: Carb backfire when release accelerator - Part 2

Happy to hear that your car is running better.

There was another thread on the forum where the screen was clogged and the sediment bowl full of crap. The owner took the carburetor apart to find lots of crap there too.
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Old 05-27-2021, 12:52 PM   #4
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Default Re: Carb backfire when release accelerator - Part 2

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Originally Posted by nkaminar View Post
Happy to hear that your car is running better.

There was another thread on the forum where the screen was clogged and the sediment bowl full of crap. The owner took the carburetor apart to find lots of crap there too.
Thanks - that was where I was going to go next in my pursuit of "sorting out" this car - a work in progress but a very satisfying pursuit!

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Old 05-27-2021, 08:25 PM   #5
Ernie Vitucci
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Default Re: Carb backfire when release accelerator - Part 2

Good Evening...A number of us just simply put a good sized magnet ( like about the size of a quarter) into the glass bowl and let it help trap what comes from the tank. It is easy to see what has attached itself to the magnet...and know when to remove the bowl and clean it out and clean off the magnet. I've had 'A's since the mid 60's on and off and I learned the magnet trick, from a guy that was about 75 in 1964...might say he was an original Model 'A' er! Ernie in Arizona
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Old 05-28-2021, 02:30 PM   #6
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Default Re: Carb backfire when release accelerator - Part 2

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Thank you Ernie for the magnet suggestion - I'll work on one of those next!


Bad news - this morning I started, did not sound good - somewhat skipping. WHile driving it was skipping so bad I turned around a block away to bring home.

Two items I ordered earlier this week in order to further troubleshoot ignition issues if needed and they arrived just in time. The first was the Lightning Rod (neon tester) to check for voltage going to spark plugs. I started, then tested 4, 3, 2 - ok - 1 - nothing. I went through all four again, and still got same results - weird. I then tested for continuity between the inside of distributor and tabs and all was good. I even tried another old body and the same results. I reassembled and tried starting and there was a he**tious boom in the carb as well as I believe the tailpipe scaring the crap out of my wife. After that, I thought I'd look at at ignition again - specifically the points. Up to this time I wasn't able to rotate the engine manually, so I just checked them for cleanliness, but then the second item - the Hand Crank - arrived. I moved the crank to a high spot on the distributor, and measured about almost minimal, if non existent opening happened. I rotated to all four points and they were the same. I then adjusted to .020 and ensured it did the same on all four high spots. Reassembled and started right up - no issue except seemed much smoother. Used the Lightning Rod and all four nodes lit up - progress! Only item I couldn't check now was a test drive as it was pouring rain outside. I am noticing a difference in response now as well when I hit the accelerator as it seems a bit delayed. I hope nothing was damaged in the carburetor on that last big bang. Any other items I should look out for if the test drive shows as in driveway - lagging accelerator or response when I hit the petal?
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Old 05-28-2021, 02:59 PM   #7
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Default Re: Carb backfire when release accelerator - Part 2

If you've adjusted your points I believe the next step would be to adjust your timing.
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Old 05-28-2021, 04:15 PM   #8
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Default Re: Carb backfire when release accelerator - Part 2

Although the point gap seemed the same on all four lobes while it was at the minimum setting, a slight wobble in the distributor shaft could easily mean that #1 was not opening. This could explain why no spark at #1. Check to see if there is any play in the distributor shaft. It is OK to have a little but not a lot.

There is no reason for the timing to change unless you or someone else changed it before the points were adjusted correctly. But check it anyway. Follow the instructions in the maintenance books.

You may want to clean out the carburetor. There are good instructions for how to do this at http://model-a.org/clean_minor_dirt.html. The same site has instructions for setting your timing and other procedures. See http://model-a.org/procedures.html.


When driving you will have to adjust the spark for the best performance. Start at about 2/3 way down. Every car is different. My car likes the spark at 3 notches from full advance. You will have to search for the knee where further advance will not improve engine performance. The same site has some good instructions for setting the timing for normal engine running, see http://model-a.org/use_carb_check_timing.html.


All this stuff becomes second nature after a while. I have owned Model A's for 60 years so it is ingrained by now. Sounds like you are getting closer to having a well performing car.
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A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.

Last edited by nkaminar; 05-28-2021 at 04:30 PM.
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Old 05-28-2021, 09:06 PM   #9
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Default Re: Carb backfire when release accelerator - Part 2

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Originally Posted by Harpkatt View Post
If you've adjusted your points I believe the next step would be to adjust your timing.

Followed this advice next, as the third item I received the other day was my Nurex wrench. Used the crank and pin method to find TDC-my first time so it was a bit tedious. I do wish I had the "bent wrench" to do the cranking as it seemed every time I got near the dimple, I would go past too quick. It took a bit of patience but I eventually reached the point where it hit the edge and down into the dimple. Looking at the relative position to where the rotor was, the timing was definitely off. After following the procedure, tightening, reassembly, attempted to start and it fired right up with no hesitation or backfiring. When the accelerator was hit, the engine responded immediately - not delayed as before. It is pouring rain right now so I'll have to wait until morning for a hopefully dry morning, and see if the adjustments and replacements that were obviously needed made a significant difference.



At this point I am amazed that this car has run what I thought "well" for this long. Hoping to see a significant improvement.
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Old 05-28-2021, 11:08 PM   #10
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Default Re: Carb backfire when release accelerator - Part 2

Hey
I was the guy with the black crud problem. Do not use the small paper filter in the glass sediment bowl. It works better without it. Take the nut off the bottom of the Zenith carb and clean the crud out of the carb. Drain the tank out and filter your gas. Then put about 1 gallon in and shake the car by standing on the running boards. Repeat until the gas is crud free. Install a Pensile filter in the gas tank and you should be good to go. I have seen a little more in the sediment bowl but not much and it's doing its job. Hope this helps.
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Old 05-29-2021, 09:41 AM   #11
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Default Re: Carb backfire when release accelerator - Part 2

Well - the weather was dry this morning so did a first run - about 20 miles. First - the starting was more instantaneous. Cold idling was much better as it was 45degrees this morning. As I went through the gears, the engine was more responsive than any good period prior. A good lesson on the importance of proper timing on these cars. As i drove more and more, I almost forgot to look at the gas gauge to see where it was bottoming out at the Zero! Quick fill up, added some MMO, and drove for another half hour without incident. I am feeling a lot better about the time and parts invested when I have this kind of result. One more day of this kind of performance, and I'll be able to reconfirm my spot in the Memorial Day Parade.


I appreciate the comments, knowledge, and encouragement along the way. I have additional parts on order for when I'll tackle the potential gas tank "contributions", and at a minimum disassemble/clean out the carburetor.
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Old 05-29-2021, 10:28 AM   #12
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Default Re: Carb backfire when release accelerator - Part 2

I hope you ensured that there is a bit of lubricant on the points cam in the distributor. There should be a bit of grease or vaseline on it, not too much. Also check the surface of the cam, it should be super smooth.
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Old 05-29-2021, 02:21 PM   #13
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Default Re: Carb backfire when release accelerator - Part 2

Congratulations and thanks for the followup. It helps all of us to know what worked.
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A is for apple, green as the sky.
Step on the gas, for tomorrow I die.
Forget the brakes, they really don't work.
The clutch always sticks, and starts with a jerk.
My car grows red hair, and flies through the air.
Driving's a blast, a blast from the past.
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Old 05-29-2021, 05:34 PM   #14
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Default Re: Carb backfire when release accelerator - Part 2

Quote:
Originally Posted by mgambuzza View Post
Followed this advice next, as the third item I received the other day was my Nurex wrench. Used the crank and pin method to find TDC-my first time so it was a bit tedious. I do wish I had the "bent wrench" to do the cranking as it seemed every time I got near the dimple, I would go past too quick. It took a bit of patience but I eventually reached the point where it hit the edge and down into the dimple. Looking at the relative position to where the rotor was, the timing was definitely off. After following the procedure, tightening, reassembly, attempted to start and it fired right up with no hesitation or backfiring. When the accelerator was hit, the engine responded immediately - not delayed as before. It is pouring rain right now so I'll have to wait until morning for a hopefully dry morning, and see if the adjustments and replacements that were obviously needed made a significant difference.



At this point I am amazed that this car has run what I thought "well" for this long. Hoping to see a significant improvement.

When you go past TDC with the crank, you can put the car in 3rd gear and rock it backward a bit and the pin will drop back in. Once it is all the way in, take the car out of gear so that it won't move on ya.


If you remove the #1 plug that will also help, but I usually don't do that. I get close and then stop to let the compression bleed off for several seconds which makes it easier to hit TDC on the first try. If I still miss, then I put her in gear as stated above.



You're on a great forum full of immense knowledge. It's like having 10,000 new friends.
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Old 05-29-2021, 06:03 PM   #15
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Default Re: Carb backfire when release accelerator - Part 2

Quote:
Originally Posted by katy View Post
I hope you ensured that there is a bit of lubricant on the points cam in the distributor. There should be a bit of grease or vaseline on it, not too much. Also check the surface of the cam, it should be super smooth.
Thank you- yes I did. After going through all this the last thing I wanted to do was more destruction from rushing through the job.
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Old 05-29-2021, 07:23 PM   #16
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Default Re: Carb backfire when release accelerator - Part 2

Its such a great news to know that your car is up and running

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Old 12-18-2021, 02:02 PM   #17
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Default Re: Carb backfire when release accelerator - Part 2

Quote:
Originally Posted by mgambuzza View Post
Thank you Ernie for the magnet suggestion - I'll work on one of those next!


Bad news - this morning I started, did not sound good - somewhat skipping. WHile driving it was skipping so bad I turned around a block away to bring home.

Two items I ordered earlier this week in order to further troubleshoot ignition issues if needed and they arrived just in time. The first was the Lightning Rod (neon tester) to check for voltage going to spark plugs. I started, then tested 4, 3, 2 - ok - 1 - nothing. I went through all four again, and still got same results - weird. I then tested for continuity between the inside of distributor and tabs and all was good. I even tried another old body and the same results. I reassembled and tried starting and there was a he**tious boom in the carb as well as I believe the tailpipe scaring the crap out of my wife. After that, I thought I'd look at at ignition again - specifically the points. Up to this time I wasn't able to rotate the engine manually, so I just checked them for cleanliness, but then the second item - the Hand Crank - arrived. I moved the crank to a high spot on the distributor, and measured about almost minimal, if non existent opening happened. I rotated to all four points and they were the same. I then adjusted to .020 and ensured it did the same on all four high spots. Reassembled and started right up - no issue except seemed much smoother. Used the Lightning Rod and all four nodes lit up - progress! Only item I couldn't check now was a test drive as it was pouring rain outside. I am noticing a difference in response now as well when I hit the accelerator as it seems a bit delayed. I hope nothing was damaged in the carburetor on that last big bang. Any other items I should look out for if the test drive shows as in driveway - lagging accelerator or response when I hit the petal?
Can you please hum a few bars on what this "Lightning Rod" is, how it works and what all it tests?
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Old 12-20-2021, 11:01 AM   #18
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Default Re: Carb backfire when release accelerator - Part 2

https://www.nurex.com/sparklite

Checks spark plug polarity.

There are others which just indicate presence of spark.
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