Busted 8N

   #1  

Tractorable

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1952 Ford 8n, saving up for a new Kubota or Yanmar
1952 Ford 8N, side mount distributor, 12V conversion.

So I consider myself to be a pretty good shade tree mechanic but I'm having trouble getting my 8N to run. It ran great for two years but now I'm having issues.

I'm getting fuel to the carb and a spark at all four cylinders but it stills runs like its firing on two cylinders. I've done everything I know how to do except to tear into the motor and start replacing manifold and head gaskets.

This is what I've done so far:

- New battery and battery cables
- New coil
- Drained fuel tank and replaced fuel with fresh gas
- Confirmed good fuel flow by removing drain at bottom of carb
- Rebuilt carb
- removed, cleaned, adjusted distributor. New points, condensor, rotor, cap
- checked continuity in distributor in six different places, all good
- new plug wires
- confirmed spark at all four cylinders
- opened spark plug gap to nearly 1/4" and still got spark
- removed and inspected governor, looked fine
- engine oil is clean and full, no sign of coolant/oil mixing
- compression is strong: 120psi, 120, 118, 115 - 90psi minimum
- verified TDC and timing mark on flywheel, points just opening at 4 deg BTDC on #1 cylinder

I'm about to push the tractor off a cliff and go buy a new Kubota.

Should I tear into the motor and replace manifold and head gaskets?

Any other ideas?
 
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   #2  

MossRoad

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Wow! I was gonna suggest compression test, but you hit that towards the end. It’s a head scratcher...
 
   #3  

pmsmechanic

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Have you checked the firing order and made sure the correct spark plug wire is on the correct spark plug?
 
  
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#4  
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T

Tractorable

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Have you checked the firing order and made sure the correct spark plug wire is on the correct spark plug?

Yes, I double and triple checked that. 1, 2, 4, 3. I can do it backwards and in my sleep now.
 
   #5  

flyerdan

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It looks like you replaced everything electrical except the spark plugs. Sometimes I've had a plug that would fire in open air, when you test for spark, but wouldn't fire under compression. Might try new plugs first, it's fairly cheap, and with those compression readings I don't think you'd find anything amiss in a teardown.
 
   #6  

motownbrowne

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Yes, I double and triple checked that. 1, 2, 4, 3. I can do it backwards and in my sleep now.

Have you pulled them while running? My neighbor's Jubilee was only running on two. He swore up and down he had the firing order right. I started pulling wires while it was running. Swapped the two offenders and it runs great.
 
   #7  

cruz54982

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Just for giggles are you sure the rotor in the distributor turns in the direction you have for the firing order turning the other way would give you 2 plugs not correct.
 
  
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Tractorable

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It looks like you replaced everything electrical except the spark plugs. Sometimes I've had a plug that would fire in open air, when you test for spark, but wouldn't fire under compression. Might try new plugs first, it's fairly cheap, and with those compression readings I don't think you'd find anything amiss in a teardown.

I actually did replace the plugs and gapped them to spec. I replaced so many things that I forgot to mention new plugs above. Thanks for the response.
 
  
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Tractorable

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Have you pulled them while running? My neighbor's Jubilee was only running on two. He swore up and down he had the firing order right. I started pulling wires while it was running. Swapped the two offenders and it runs great.

That's something I haven't tried. It just barely runs right now and I'm not sure it'd run long enough to try that. I'll give it a try though. Thanks
 
  
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Tractorable

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Just for giggles are you sure the rotor in the distributor turns in the direction you have for the firing order turning the other way would give you 2 plugs not correct.

Good call, however, the rotor turns counterclockwise and I'm counting CCW when checking the correct spark plug wire routing.

My current thinking is a possible vacuum leak in the intake manifold.
 
 
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