engine missing ---thoughts needed

H

harryc

Senior Member
My car has ben setting for a month or so and when I stared it yesterday it stumbled and missed terribly. M y first thought, knowing this car, was maybe this Calif gas had caused a jet to plug--( it has before). I cleaned and checked the carb (tillotson) and adjustments and no change so I switched carbs---no change. I looked at the plugs and they looked sooty so I changed the plugs---still runs rough. I have a modern distributor cap--I switched the cap, rotor and wires--still runs rough. I put in new points (modern) .018 gap----no change. I took the distributor out and took it apart to see if maybe it's shorting out someplace. It didn't seem to be so I tried another distributor--no change so I switched back to the first distributor. In shorting the plugs while running it seems to always be only number one that is not firing --no change so now I am starting to get worried. Thinking maybe I have a stuck valve in number one I checked the compression.....120 lbs. Any ideas---It has to be something very simple but it is escaping me. I forgot to mention that I drained and put in fresh gas.----thanks
 
Im no pro like the others, but i have been reading a lot lately trying to learn the Model A, it looks as you changed everything but the condenser???? Kinda sounds like the same symptoms others have had with a bad condensor
 
Condensers don't go bad very often, but you might hook one up externally to see if that helps. Just connect it between the point arm and ground. This can be points side of the coil.
 
Jacksonlll said:
Condensers don't go bad very often, but you might hook one up externally to see if that helps. Just connect it between the point arm and ground. This can be points side of the coil.
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While on the road and in a quick need for a condenser, I have mounted a condenser on the firewall on the coil. I used the points side of the coil to mount the new condenser on. Worked so good that the last one I left mounted there, it was left there for about 20 years. I always carry a 1957 Ford 12 volt condenser with me. Easy to purchase and easy for a quick "farmer's installation, and it works good.
The intake manifold leak suggestion is another one where the engine won't hit on a couple of cylinders when idling, but it smooths out at higher speeds. Also if you pull the choke on a little, the missing cylinders will start hitting again, just because now they are getting a richer fuel mixture.
 
If you remove the spark plugs you can see the valves through the spark plug hole in the head. I believe you are correct when you were thinking a stuck valve may be causing your problem. If you see a valve is not not closing completely you can reach inside the spark plug hole with a bent steel rod to try to get it to move. I have had this very same problem with my Model A when it sat over the winter.

I was fortunate to get the stuck valve to move by using this method. I now add a few ounces of Marvel Mystery Oil to each tank of fuel. I also never use ethanol fuel in my Model A. Good luck, and let us know what you find.
 
I wouldn't guess a condenser was the problem if it has been proven that only #1 cylinder is not firing.

120 pounds of compression in #1? Seems about 2X normal. Are you sure? What do the other cylinders read?
 
Try some MMO in your gas. Could (should) help with sticky or slow valves.

I know what other people will say, but it works on our cars.

Try cheapest fixes first. Enjoy.
 
WHN said:
Try some MMO in your gas. Could (should) help with sticky or slow valves.

I know what other people will say, but it works on our cars.

Try cheapest fixes first. Enjoy.
Click to expand...

Yes, a slow to close valve can have good compression, but miss on a running engine. I always use gas without ethanol crap, and add 4 ounces of MMO to each 10 gallons. No sticking valves ever.
 
A broken valve spring will do that on A too.At cranking speed the valve will close just from gravity,and then the compression pressure will hold it shut until the cam picks it up again.
 
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by changing the distributor, you have already eliminated the points, condenser and ignition wire or all elements in the distributor, right??? if a wire was loose on the coil the missing would be here and there not just on No. one.
You are sure it is only one, you checked the spark on all four and one was the only that had an obvious miss fire???

never ran into a stuck valve but sure sounds like it could be a issue.

have you tried opening or closing the choke idle valve a touch

Good Luck DRC
 
I tried running it again to see if it might have a vacuum leak( I don't think that's the problem). It was missing randomly on other cylinders this time. Barely runs. I checked the points and each plug is sparking but very very weakly. Could this be a coil issue ? I will find out. The head is a Winfield --no idea what the compression is or if the 120 registered on the gauge is accurate. I just wanted to know if it had anything to rule out a stuck valve--back to work
 
Wonder if there is an intermittent short behind the instrument panel.
Loose connections. Is the ignition switch original popout, or an aftermarket?
 
1243------I have checked everything and double checked. I hot wired it directly to the coil to eliminate any loose wiring shorts---still missing. I tried a new coil --still missing. I rechecked the CR and its around 120 on all cylinders--Its missing on all the cylinders but very irratic and hard to isolate. I'm not sure what I haven't checked 2 0r 3 times already. It should be running fine!!! when I pull the plugs they all appear to have been firing although #1 has some raw gas on it, When I first start it sounds as though its going to be ok then after about 4 or 5 seconds it starts bumbling and missing. It has good gas flow. Even if it didn't it should run ok for 15 or 20 seconds until the carb emptied. Yes I have checked the line and it is not going into the carb too far.---more thoughts?
 
do you have a intake manifold with the vacuum port on it? might be time to hook up a vacuum gauge while its limping - that can tell you HOW the valves are closing among a bunch of other things.

https://www.google.com/imgres?imgur...ved=0ahUKEwjVirmr7K_XAhWf0YMKHfHaCJMQ9QEIKjAA

stupid question but are you sure a critter didnt make a home in your muffler while it sat for a month? restricted exhaust can cause all sorts of issues (vacuum gauge will show that as well)
 
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