Running on two

[Quigley1930]

My coupe which was running great last Nov. when I stored it now is really running rough. I have timed it to be spot on and get a nice blue spark from the coil wire to a head nut. I have tried three different carbs. I am using ethanol free gas. After starting with great difficulty it appears to be firing on 1 & 3 only. it backfires and belches black smoke from the carb. I do have a nice spark at the points. I'm stumped and any help will be most appreciated.

Sewall

[Tom Wesenberg]

I would do a compression check and if that shows good, then do a vacuum check at idle and higher RPM. A slow to close valve can show a good compression reading, but close too slowly for the engine to run well.

Spray the valve with some Kroil or such if it is hanging up.

[J Franklin]

If you suspect sticking valves, this is the time to give Marvel Mystery Oil a chance to impress you.

[Quigley1930]

Compression is:
#1-65lbs
#2-70lbs
#3-65lbs
#4-70lbs

I really don't know how to do a vacuum test. I usually use MMO but can't remember if I put any in the last time. 80 year old brain ain't up to snuff.

Sewall

thanks for the replies so far.

[C26Pinelake]

Originally Posted by Quigley1930

Compression is:
#1-65lbs
#2-70lbs
#3-65lbs
#4-70lbs

I really don't know how to do a vacuum test. I usually use MMO but can't remember if I put any in the last time. 80 year old brain ain't up to snuff.

Sewall

thanks for the replies so far.

If you can't remember use some more, it can't hurt anything. Wayne

[Mike V. Florida]

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True backfiring through the carb is an indication of; lean mixture, sticking valve.

Have you tried also tried adjusting the GAV and have you checked for spark at EACH spark plug? How about the condenser? That can cause erratic running.

[Tom Wesenberg]

Have you layed a screwdriver between the head and spark plug to short them out one at a time to see if each one is firing?

[700rpm]

Pour some MMO into each cylinder and start it up and see what happens. Might be sticky valves.

[Barber31]

The black smoke is from the non firing cylinders being flooded and igniting out of sequence. Based on what you said checked out good and if the other 2 cylinders are firing then I would say the problem is after the rotor cap. I would check the dizzy cap for cracks or sooted up contacts.

[tbirdtbird]

"The black smoke is from the non firing cylinders being flooded and igniting out of sequence"

????

how exactly is that possible

[C26Pinelake]

Originally Posted by Barber31

The black smoke is from the non firing cylinders being flooded and igniting out of sequence. Based on what you said checked out good and if the other 2 cylinders are firing then I would say the problem is after the rotor cap. I would check the dizzy cap for cracks or sooted up contacts.

Please explain lighting out of sequence, you have me confused now. Wayne

[Quigley1930]

Tom, that is how I found 1 & 3 to be the only ones firing. I've turned the GAV every way but loose! Really trying at about 1/4 open. Will try another cap.
Thanks again everybody.

Sewall

[tbirdtbird]

pls post pix of plugs 2 and 4

[Domino]

Sounds like stuck valves to me. So check the compression. Good luck.

[tbirdtbird]

follow along.
He already checked and posted compression readings

[Barber31]

Originally Posted by tbirdtbird

"The black smoke is from the non firing cylinders being flooded and igniting out of sequence"

????

how exactly is that possible

Maybe flooded was a poor choice of words but the engine is still operating according to the op. So the fuel/air mixture is still filling the non firing combustion chambers no matter what. Adding more fuel to a non firing cylinder is producing a rich or "flooded" mixture that when ignited produces a very dark exhaust gas or black smoke. I have no idea if it's igniting in the cylinder or exhaust pipe or where but it's obviously exiting thru the carb as was stated. Either way it's definitely not in sequence or else it wouldn't be exiting thru the carb and causing backfires or belches. If it was in sequence it would be pushed out thru the intended exhaust port. Do you really not know what's happening in a backfire or were you being condescending? If I'm wrong please correct me. Im always open to learn something new.

[Quigley1930]

Cutting grass today so no Model A work. Tbird it's a hassel for me to post photos but all the plugs were black and sooty. I've cleaned them. I did put some MMO in each plug hole today. Granddaughters soccer game tomorrow so may be Monday before I get back on it. I really appreciate y'alls help.

Sewall

[jm29henry]

Try changing your condensor

[Quigley1930]

Sorry to be so long getting back to y'all. jm29Henry suggestion was the answer. New condenser solved the problem. Thanks again everybody.

Sewall

[Clem Clement]

Now take granddau for a ride!