Intermittent Run Issue

Jim in Western MI · Aug 3, 2021

While repairing #1 8N and its overheating problem, the #2 8N has developed its own issue. This is a 12v, front mount, OE points tractor that even has a Royse carb on it and has worked flawlessly for several years. Last week I started it (normal start) and was letting it warm up at a fast idle for a couple minutes while I rolled a finish mower over to attach. Suddenly, it began to miss and run very rough (not a rhymthic miss like a bad or fouled plug, but intermittent). Almost cut off several times, but stayed running on a hit or two. I was able to feather the throttle and once got it up to normal working rpms with no misses for several seconds before going back rough, with occasional backfire. Finally it cut off, but started again with same roughness. Concluded it was the points as that has happened before, so ordered from this site the premium Blue STreak (at a very premium price!). Disappointed when they came that they had the plastic arm, not the phenolic arm; but installed them anyway and got exactly the same symptoms. Seems electrical since fuel flow at carb drain was excellent and has been without fuel issues. So I checked voltages: battery 12.6, downstream of key switch 12.3, and 12.0 at the coil. That might be a little low, but I think it should work at those voltages. Jumped hot wire to coil lead from battery to make sure, no change.

Don't know the symptoms of a bad condenser, I thought they either worked 100% or not at all. And from reading here, coil problems usually show up after it gets hot and this issue exists at start up. Anyone had this experience?? I need help..., grass is growing and both 8N's are down. That's never happened to me with these reliable machines.

R Geiger · Aug 3, 2021

(quoted from post at 14:31:42 08/03/21) While repairing #1 8N and its overheating problem, the #2 8N has developed its own issue. This is a 12v, front mount, OE points tractor that even has a Royse carb on it and has worked flawlessly for several years. Last week I started it (normal start) and was letting it warm up at a fast idle for a couple minutes while I rolled a finish mower over to attach. Suddenly, it began to miss and run very rough (not a rhymthic miss like a bad or fouled plug, but intermittent). Almost cut off several times, but stayed running on a hit or two. I was able to feather the throttle and once got it up to normal working rpms with no misses for several seconds before going back rough, with occasional backfire. Finally it cut off, but started again with same roughness. Concluded it was the points as that has happened before, so ordered from this site the premium Blue STreak (at a very premium price!). Disappointed when they came that they had the plastic arm, not the phenolic arm; but installed them anyway and got exactly the same symptoms. Seems electrical since fuel flow at carb drain was excellent and has been without fuel issues. So I checked voltages: battery 12.6, downstream of key switch 12.3, and 12.0 at the coil. That might be a little low, but I think it should work at those voltages. Jumped hot wire to coil lead from battery to make sure, no change.

Don't know the symptoms of a bad condenser, I thought they either worked 100% or not at all. And from reading here, coil problems usually show up after it gets hot and this issue exists at start up. Anyone had this experience?? I need help..., grass is growing and both 8N's are down. That's never happened to me with these reliable machines.

I would say condenser!

Jim L WA · Aug 3, 2021

I know you said fuel flow was excellent at the drain plug, but I'll ask anyway. You aren't running low on gas are you?

Joe.S.AK · Aug 3, 2021

Jim,

You have fuel flow from the tank, through the bowl, through the fuel line, through the carb intake screen and through the carb bowl drain plug. Good.

Do you have flow through the rest of the carb to the cylinders? A piece of Schmuuu could be randomly restricting flow there. Simple cleaning fix if that's so.

If it's a plugged tank vent it should "heal" if you crack the fuel cap while it's fighting "The Miseries".

- Joe -

This post was edited by Joe.S.AK on 08/03/2021 at 09:28 pm.

Jim in Western MI · Aug 4, 2021

Fuel supply is fine, problem occurs at or a couple minutes after start-up. So vacuum lock in not an issue. Mr. Geiger, what are the indications that a condenser is bad? Thanks.

R Geiger · Aug 4, 2021

(quoted from post at 08:16:22 08/04/21) Fuel supply is fine, problem occurs at or a couple minutes after start-up. So vacuum lock in not an issue. Mr. Geiger, what are the indications that a condenser is bad? Thanks.

have JD crawler that I fought a very similar problem, it would start and run for a bit then start missing. easy to change! Back in the day the points and condenser game as a set and I always changed them out as a set. Not so these days, and I think people overlook them, I know I did for a few days!

Jim in Western MI · Aug 4, 2021

I learned changing points on a '64 404 Peugeot..., and the set always included a condenser which I changed out as well. That car seemed
to eat points, had to be changed about every year. One time I did the job and it wouldn't start, run, or even hit. My father (the
real mechanic in our family) said to put the old condenser back in because you knew it was good. Which I did and it started fine.
So since then I just change points, probably where I concluded condensers are 100% or 0% good. Seems like I remember my Dad charging
up condensers by grounding the body to a battery and touching the wire to 12v positive, and then laying it out on the counter at his
parts place. When someone idly picked it up and touched the wire and the body, it would discharge and shock them.

Jeff Hamilton · Aug 5, 2021

Jim - exact same issue with my tractor last week. I thought points, checked and they were a little dirty and gap was too small, so I corrected. No help. I thought fuel. Checked the screen in tank, screen at carb and did the plug out test - fuel fine. Installed new points - NG. I added a new coil wire, no help. New rotor and cap, no help. Changed the condenser -BINGO! Problem solved.

a32vickyhotrod · Aug 5, 2021

Have you ruled out water in the fuel?

Jim in Western MI · Aug 5, 2021

Fuel is fine. I'm pretty sure it is the condenser as Mr. Hamilton and Mr. Geiger have suggested. Spent a couple days trying to find
one locally that would fit, but no luck and have ordered from YT. I once had a cross-check chart of auto parts store numbers for 8N
parts, but cannot find it, and the mounting hole on the ones I could find are not correct for the 8N application. Will report in a few
days.

Jim in Western MI · Aug 5, 2021

Thank you for the report; hopefully that will be my fix, too. Have to wait a few days to get one as I could not find a match at any of the auto parts stores.

Intermittent Run Issue

Jim in Western MI

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R Geiger

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Jim L WA

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Joe.S.AK

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Jim in Western MI

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R Geiger

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Jim in Western MI

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Jeff Hamilton

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a32vickyhotrod

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Jim in Western MI

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Jim in Western MI

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