Exhaust popping, losing power when hot

[jimjumper]

Been trying to revive an old 8N after sitting for 7 years. 6 volt, with front mount distributor. Have replaced a fair bit of parts, new gas tank, fuel line, sediment bowl, and all 3 screens. Passes fuel flow test from carb without problem. New points, condenser, distributor, square coil, and battery. Got it started and running well (new carb) and discovered that the genny was not charging so it would start running rough after about an hour when the coil started not getting enough voltage. Or at least I assumed so. Took the genny to an expert on 6 volt systems (he's worked on a lot of N's and Model T's) and installed new genny with a cut-out instead of the VR. Installed it and wasn't getting power to the coil and discovered the wire from the ammeter to starter relay was bad! Replaced that. Started it yesterday and noticed the exhaust slightly popping after it warmed up. Ran it for an hour and could still hear the popping. Valve maybe? Added some SeaFoam to the fuel and ran it for an hour this morning (ambient heat about 100') and then heard it really popping and occasionally backfiring. It was stalling on the drive to the barn (adding choke made it worse) but got it parked and noticed the ammeter fluctuating at idle from 0 to -5. I assume thats the points opening and closing? Let it cool for 2 hours and started it, no popping or back fire! Haven't ran to full warm up yet but am inclined to think the coil is overheating? Any way to check other than buying a new coil? The one on it is new from Tractor Supply but I haven't heard good things about their parts. I'll also check spark in a few minutes when I take it out and get it warm again.
Something I forgot to add is that the battery is staying constant at 6.2 volts of charge so it appears the genny is working as its supposed to.

 

[Topzide]

Could be a fuel issue. Are you using ethanol or non-ethanol? The alcohol in ethanol could be the cause of issues. Not saying that a burnt valve could be causing this running issue. Clean up the plugs real good and gap them. Keep us updated.

 

[jimjumper]

Just started it again. Ran fine till I put a load on it and then started stalling. Immediately, within seconds checked fuel. Good flow from carb. Checked spark next, orange spark on spark checker for all 4 cylinders. Battery is full charge. Don't think its points, I've checked them so many times my hands are hamburger! I'll swap the coil out for the original next and see what happens.

 

[EdGooding]

Something I forgot to add is that the battery is staying constant at 6.2 volts of charge so it appears the genny is working as its supposed to.

If you are seeing 6.2v when running then the genny is NOT working as it should. You should be seeing more like 7.3. When you installed the new genny and cutout, did you polarize the charging system?

 

[jimjumper]

If you are seeing 6.2v when running then the genny is NOT working as it should. You should be seeing more like 7.3. When you installed the new genny and cutout, did you polarize the charging system?

Actually I am seeing that with the tractor off. Before, I was only getting 3-4V to the coil and it wouldn't power the points, so no start until I put a charger on it. Then it would run until the battery was low again. Haven't had to use the charger for starting since the new genny.

 

[EdGooding]

Actually I am seeing that with the tractor off. Before, I was only getting 3-4V to the coil and it wouldn't power the points, so no start until I put a charger on it. Then it would run until the battery was low again. Haven't had to use the charger for starting since the new genny.

What are you reading with the engine running?

 

[wolc123]

Check the compression on each cylinder. Those sound like the symptoms mine had when it needed a valve job.

 

[jimjumper]

Swapped coil back to the old one. Much better. Ran up and down a steep hill in my back pasture and it reacted well to the governor kicking in when it got steep. Would have died before. Still not as bright a spark as I would like but I might just get my last field mowed before the Fire Dept. starts writing me tickets. I will run it again this afternoon as soon as the temp drops below 95 and see what happens

 

[jimjumper]

Never mind! As usual with this beast, something else broke and I'll have to get back to its running problems after I get that fixed. Anybody know how to remove a broken over-run coupler? Already pulled the set screw and the Zerk fitting but can't beat out the roller pin holding it. Or am I doing it wrong?

 

[wolc123]

Never mind! As usual with this beast, something else broke and I'll have to get back to its running problems after I get that fixed. Anybody know how to remove a broken over-run coupler? Already pulled the set screw and the Zerk fitting but can't beat out the roller pin holding it. Or am I doing it wrong?

I lost the O/C coupler for mine years ago. You might have to rotate it, to line up the roll pin, then drive it out with the right diameter drift pin and a hammer. I recall it having two different shaft sizes so that it would work with standard implement pto’s.

I know just how you feel about the old Ford. My 1951 Ford 8n is down and out right now with some type of electrical issue. That tractor is loads of fun when it’s running but is a real bear to do maintenance and repairs on. Even an oil change is a pain. And what’s up with having to remove the hood and gas tank anytime you need to do just about any work on it ?

I’ve said it many times, because there’s lots of truth to it: My favorite thing about owning one Ford and one Farmall tractor is the appreciation that they give me for the John Deere’s which have done most of the work at our farm, since grandpa got rid of his last team of horses, back in 1950.