8N won't run

Hi everyone, new to the forum, but always check it for answers. I have a ’52 8n with a 12 volt conversion that has been a reliable work horse for the last decade, but recently has decided to change our relationship. Last week it was running great, shut it down it sat for two or three days, went to start it and she sputtered and wouldn’t start. I checked the usual suspects, but nothing. I replaced the points, wires, condenser, and plugs about two months ago. It will run briefly at a low rpm, but dies. During my investigation I have checked:
-the spark, jumps ¼” gap on tester
-spark timing with compression stroke-good
-cleaned out and put a kit in the carb and set to specs
-energized the coil directly to the battery, no change
-checked and reset the points to .025
-put in fresh gas and fed from gas can directly, so the tank is totally off
-there is a hint of fuel smell in the oil

I am out off easy fix ideas. Could use some help. I put a new coil on it out of desperation, which made it run longer, but still poorly.

As soon as it stops....not 5 minutes later.....check for spark w/ your tester. Turn the key on, crank the engine & look at the ammeter. What is the needle doing? Does it show a constant discharge, no movement at all, or does it move back & forth slightly? Next, hook up your spark checker, turn the key on & crank the engine. If the spark jumps the 1/4” gap, you probably don’t have a spark problem. If it won’t jump the ¼” gap, you have a spark problem. If the ammeter needle shows a constant discharge, or doesn’t move at all, that also tells you that you have a spark problem. Jump the ignition switch w/ your jumper wire & see what happens. If it runs, you found the problem. If it doesn’t have spark after you jump the ignition switch, post back for more info on further troubleshooting. (and do not forget to turn the ignition switch off; see tip # 38)

If you have spark, check for fuel by removing the bolt in the bottom of the carb. Get a can & put it under the carb. Remove the bolt in the bottom of the carb; as long as the fuel is turned on, you should see gas flowing out of the carb. Let it run for at least 30 seconds. If it’s a dribble, or runs for 5 seconds & stops, or none at all, you have solved half the problem: it’s fuel related.


Do you have battery voltage across the points when they are open? Verify the gap on the points at .025. Then, dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. (I always spray my feeler guage blade off w/ contact cleaner.) Make sure you have voltage across the points, as in past the insulator on the side of the distributor. That is a very common failure point on sidemounts, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. If you find the short there, the Master Parts catalog lists everything you need on page 154. You can make the strip and you could also make the insulators as well. But, somethings are just easier & in the long run cheaper to buy. Get the strip, 12209, screw 350032-S, 12233 bushing & 12234 insulator & just replace it all. If you just replaced the rotor & lost spark, put the old one back in. Insure that the rotor fits firmly on the shaft & that the little clip is there. Make sure the distributor cap is not cracked & doesn't have carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. In fact, replace it temporarily w/ a plug wire. Next, remove the secondary coil wire from the center of the distributor cap, turn the key on & crank the engine while holding the end of the wire 1/4" from a rust & paint free spot on the engine. You should see & hear a nice blue/white spark. If not, you have a bad coil or condenser. Just put the old condenser back in to eliminate that as a possibility.

Lastly, as it's a 12v conversion, what resistors are you running?

Post back w/ results; I'll be interested in what the problem was.
75 Tips

since it runs at all ( short run, low rpm ) that means timing and fire order are off the table .

You mentioned running it hotwired..that would take the resistor issue off the table.. plus you said good spark. if that is so.. I'd procede to fuel.

will she pick up any rpm on full choke?

do you have a can of start fluid to test her?

Thanks soundguy--Yes, used start fluid. It runs briefly, but it will also run without it. It still sounds rough though, like one cylinder is out. I have completely cleaned and put all new parts in the carb. Also made sure the needle valve is opening. I am dissapointed that the new kits do not have a wire to pull the needle down, just fat one that gravity is supposed to drop. The float bowl has fuel in it. Full choke kills it. Its strange that it runs longer now that I have the new coil on it, but still badly.
I am not sure what else I can do about the carb. I cleaned that thing well enough to eat off of and blew out all the passages

Thanks Bruce. I have done all of what you mentioned already except check the ammeter status, and check the spark right after it shuts down, but its getting good spark just cranking it. Also the points aren't new its been running great with them for two months.
Also I removed #1 plug, put a tester on the wire and cranked it while holding my finger over the hole and the spark to compression stroke seems to be spot on.
oddly I can't find any resistors on the tractor. Whoever converted her either hid them well, or ignored them entirely. Everything is tied to a terminal block near the ammeter.

" and check the spark right after it shuts down"

You really need to do that.

Hook up the spark checker & start the tractor.

Then see what happens when it dies.

You're losing spark somewhere.

The likely suspect is the distributor insulator.

" I can't find any resistors on the tractor."

That's good; you have a side coil & it's likely 12v, so no resistors needed.
75 Tips

it may be that you are actually ONLY running on 2 cyls. it will run on 3 with a noticed miss. it will rumble on 2.

pull a plug wire at a time and see if you find one or 2 that make it not start at all, or 2 that make no difference in starting?

the 2 that make no difference.. thumb test the plug hole for compression. could have 2 hung intakes...

Update. I had my mechanic friend do a compression test and a leak down test and all was good. He thought the spark looked weak or at least in consistent. It turned out this tractor had a 3" Perolite distributor that I could never find parts for, so I opted to replace it with an aftermarket standard Dist. and pair it with a Pertronix electronic ignition. I static timed it and she fired on the first try. Still needs some fine tuning, but runs fine. Thanks for the help.