Gunfight at the OK Corral

[4118truck]

Well, that it what it sounded like. I'm new to the Model A world. My 31 pickup had been running great and then, all of a sudden, started to backfire like there was a gunfightt. Lost power, but fortunately, was able to coast home. The next day, it cranked fine and ran. Since then, it has been getting progressively worse.

On startup, I will get several loud bangs. If I hold the choke partially out, at startup, it seems a little better, but still get loud bangs. Will not idle and requires pumping the pedal to keep running.

Last time I cranked it I got a smell like burned popcorn, and now will not fire at all.

Where do I start?

[Clem Clement]

check your points

[1930artdeco]

Don't forget about the condenser...

Mike

[johnsor]

I had the same problem last year. I did all the ignition and carb things to no avail. In changing the oil, I discovered coolant in the oil. Pulled the head and discovered a bad head gasket which allowed the plugs to get wet thus delayed loud ignition and backfire when cranking over. Cleaned the deck and head up, installed a new head gasket, and now starts and runs like a top. No back firing on start up.

[Tom Wesenberg]

Start with a diagnosis. Hold the coil wire 1/4" from a head nut. Do you get a hot blue spark while cranking with the key on?

[afuncar]

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Is your spark lever advanced after you start engine?

[Brentwood Bob]

do you adjust the dash adjustment as the pickup warms up. richer for the back firing.
could be you have debris in the carb jets now. Bob

[jimalabam]

All above posts are very good. Start from the top and eliminate the problem...

[1931 flamingo]

Vacuum leak at the manifolds??
Paul in CT

[Keith True]

My vote is for a bad connection somewhere.If you have a fuse check that first.A bad fuse or a bad connection will put 30-40 volts to the coil,that will give you some big backfires.Connections at the starter,terminal box,ammeter,etc.can all do it.It can be a lot of things,but simple things first.I worked on a car a couple of years ago where the owner had replaced the head gasket,had the head planed,the manifolds planed,had the carb done,had the dist.redone,and finally replaced the timing gear.His problem was a bad connection of the main feed wire at the starter.The terminal was crimped on the insulation,not so much on the wire itself.I found it when I started yanking on connections.

[Patrick L.]

After checking for a good spark, check for good fuel flow. Remove the inlet to the carburetor making sure the line only protrudes past the ferrel about a 1/16". Open the valve and empty about a gallon of fuel into a jug.
If the flow is good, then the problem could be a dirty carburetor. If the flow is not good then its in the fuel supply system somewhere from the gas cap [ not venting], fuel tank, shut-off, sediment bowl.

[rocket1]

do a compression check,bad exhaust valve?

[Mitch//pa]

i am with tom to start with a diagnosis
what kind of lower distributor plate are you running wired or wireless?
i use an inline spark tester to watch the pattern and uniformity of the spark to the dist cap while running when the problem occurs.

[4118truck]

Thanks for all the advice. Going to start with the electrical, first. From the coil down.

[James Rogers]

Sounds like the fuel line is plugged and the carb needs cleaning.

[Hugh in NC]

When mine sounded like that, it turned out to be worn bushings in the distributor that was causing the misfires.

Hugh

[daveymc29]

I must agree with the bad connection. I drove to TX from CA in 2008. Backfire occurred after driving fine for a tank of fuel most every day. Changed carbs, distributors and tightened anything I could. Made it home under protesting most of the way. Then around here it ran fine for about six years then back to backfiring. This time I used a clear cap and watched as I would wind it up. At about 1500, No. two would cease firing and at 1800 number one would also quit. I found that the wire connection on my alternator was not holding the wire tight. Crimped it and problem solved. Just my experience, very frustrating. The nut on the Alt. had been checked numerous times and was tight.
Daveymc29

[4118truck]

As soon as we can find time, at the shop, with all the customer's cars, we will tackle this. Sometimes it's good to be busy, but other times..... And I was supposed to be retired.