What's Wrong

[johnsor]

Recently when I try to start my "A" when it's cold there is a series of very loud backfires. After numerous repeated try's, it will finally start and run rough at a slow throttle setting. After it warms a bit, it will finally smooth out and run fine at any throttle setting. Shut it off and restart while it's warm and it runs fine. I checked the timing and it's spot on as can be noted once it warms up a bit. Could there be an ignition component causing this when it is cold? What might I check?

[msmaron]

have you checked the fuel line and carb for junk and rust in the line? do you have rust in the tank that is blocking it…are you running to rich?

[J Franklin]

sounds like it is too lean a mix when cold. what procedure do you use to start it?

[Patrick L.]

Are you used to cold starting ? Most open the GAV a bit more [ .5 to 1 turn] and you may need to use more choke. I know this simple, but, had to ask.

[johnsor]

Living in northern Wisconsin and running my A's well into November over the past 65 years, I am familiar with cold starting procedures. It's the extreme backfiring when cold that has me puzzled. Timing is fine as it runs and starts great when warm. I've never had this problem before. Process of elimination I guess. I'll try opening up the GAV somewhat tomorrow morning.

[Marco Tahtaras]

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Any chance you have a repro choke rod? Many years ago a buddy had problems with a project. When I went over to help him check things out we found the GAV was fully closed and when he was opening it for starting only the knob was turning so the valve was still stuck closed.

[Fred K-OR]

Originally Posted by johnsor

Living in northern Wisconsin and running my A's well into November over the past 65 years, I am familiar with cold starting procedures. It's the extreme backfiring when cold that has me puzzled. Timing is fine as it runs and starts great when warm. I've never had this problem before. Process of elimination I guess. I'll try opening up the GAV somewhat tomorrow morning.

Could this be a sticking valve? This is a total guess on my part and I am no expert. Has the engine been reworked lately or is this an older rebuild?

[Purdy Swoft]

I'm guessing maybe a vacume leak that goes away when everything gets warm and expands.

[johnsor]

I'll check for that Purdy, but seems it must be something going on in the ignition components somehow. Problem is I don't have much time to test or analyze the problem as it self corrects as it warms up. It sure makes a he-- of a racket on cold start-up.

[J Franklin]

Let's analyze this. Does it backfire out the tail pipe or in the carb? Are the points clean and gapped .020?

[BILL WILLIAMSON]

"Maybe" the distributor body spark path to # 4 cyl. is arcing out & up to # 3 spark plug connector strap. Check it in the dark with the engine COLD. Bill W.

[johnsor]

Good suggestions J. Franklin and Bill. I am alone when starting so hard to tell if the backfire is coming from the carb or exhaust, but I'll try. Bill, I think your suggestion may be most valid. Now that I think of when the problem first occurred, I think it coincides when I recently installed the manifold heater for the season. To do so, I removed the distributor top and side. Maybe I didn't get it re-seated properly, or it may be bad. I'll install another body I have. I feel confident that it's an ignition issue. When I find the problem I'll repost. Thanks to all for your thoughts.

[Clem Clement]

Carb loose?
Does anyone make the clear dizzy top any more? That was neato to watch the spark jump. When there is a spark problem you can surely see it with the clear cap. You can cut the sides off a cap and use that to check the spark.

[Steve Wastler]

Clear dizzy cover isn't made currently, they've been selling for about 150 on eBay.

[tbirdtbird]

too lean

ignition problem won't go away when hot