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.

 

[jimjumper]

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.

At least the later models had the side mount distributor. I know every time I reach in for that front mount distributor to do something with it, I'm gonna need a bandaid or 2!

 

[Paystar]

Not saying it is your issue, but one of my Allis CA's was "popping" but otherwise started and ran fine. I just had to do a valve set and it went away.
On mine, I could hear the popping through the intake.

 

[EdGooding]

At least the later models had the side mount distributor. I know every time I reach in for that front mount distributor to do something with it, I'm gonna need a bandaid or 2!

Do you remove the distributor to tune or maintain it?

 

[alexpops]

Valve or spark timing. If you set the point & plug gaps right and you got a good condenser (lots of complaints about cheap chinese made condensers), setting timing is the only remaining thing to the tune-up. You said you replaced the distributer -- I'm assuming the cap, how about the rotor? If you replaced the whole distributer, or removed it, did you line it up the same on reinstall? If valve lash is at specs & springs/seats/rocker arms are ok, try advancing the spark timing if the pop is exhaust/****** if intake & carb popping. Any arcing on the wires? If none of those fixes it, your next step would be to check timing chain/gears for proper crank/cam positioning.

 

[rScotty]

Valve or spark timing. If you set the point & plug gaps right and you got a good condenser (lots of complaints about cheap chinese made condensers), setting timing is the only remaining thing to the tune-up. You said you replaced the distributer -- I'm assuming the cap, how about the rotor? If you replaced the whole distributer, or removed it, did you line it up the same on reinstall? If valve lash is at specs & springs/seats/rocker arms are ok, try advancing the spark timing if the pop is exhaust/****** if intake & carb popping. Any arcing on the wires? If none of those fixes it, your next step would be to check timing chain/gears for proper crank/cam positioning.

Spark Timing is the first thing I would check. Setting it takes a timing light and one screwdriver. You just loosen the distributor and then tighten it when the light shows you the right position. The only mechanical check is to verify that the advance is working.
The whole whole timing procedure doesn't take 15 minutes.
Anyone who has a timing light can do it if you never have.
Spark timing is rarely required unless you have been doing work on he distributor work.
rScotty

 

[EdGooding]

Spark Timing is the first thing I would check. Setting it takes a timing light and one screwdriver. You just loosen the distributor and then tighten it when the light shows you the right position. The only mechanical check is to verify that the advance is working.
The whole whole timing procedure doesn't take 15 minutes.
Anyone who has a timing light can do it if you never have.
Spark timing is rarely required unless you have been doing work on he distributor work.
rScotty

That process does not work for the Ford front-mount distributor. You have to static-time them and you can do this with the distributor off the engine and on your work bench. You can get a tool to help with this on eBay: Locking & Align Tool for Timing Front Mount 8N, 9N/2N Ford Tractor Distributors. | eBay

 

[DarkBlack]

If it was ignition timing it should have the problem both cold and hot, not just when it’s hot.

 

[rScotty]

That process does not work for the Ford front-mount distributor. You have to static-time them and you can do this with the distributor off the engine and on your work bench. You can get a tool to help with this on eBay: Locking & Align Tool for Timing Front Mount 8N, 9N/2N Ford Tractor Distributors. | eBay

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Yes, it would be nice if other manufacturers had copied Ford's lead and designed a keyed system so the distributor could only be assembled in one way. But there are enough downsides with modern gasoline that maybe we should be glad they didn't.

On lots of early engines, using a timing light for the first time requires mounting a pointer, a degree wheel, and painting a few marks on flywheel or engine pulley.

Paintng or filing timing marks on an early engine turns a 15 minute job into a two hour job the first time. After that, it's simple again.

But I wasn't saying that the popping was caused by timing. What I was sayng is that when you are looking for a problem it makes sense to start with the simplest and work towards things that are more complicate . For a mechanc, that is ignition and ignition timing - because the most common culprit in hot running if the radiator is doing it's job retarded ignition. Next comes another look at the cooling, the radiator & thermosta. Followed by carburation where lean running like a leaky intake manfold or plugged jet can cause overheating and those also can cause pre-ignition popping. Some time during that process we check for burnt or valves not sealing for some reason with a compression check.
All of these things are still in the realm of the home hobby mechanic, and my bet is that one will cure it.
But it needs a systematic approach, not a shotgun diagnosis.

 

[careyo63]

I thinking Head problem. Bad Gasket pressuring up the Sys. and getting hot to a bad/burnt, valve/Valves not seating. Hot or cold should be the same I agree on a timing problem. Getting hot is a good sign of a problem.

 

[jimjumper]

I've narrowed it down to a specific at least. I am getting a weak spark when it starts and then as it runs the spark gets weaker as the battery dies. I replaced the generator and VR already with a new generator and cutout but it doesn't appear that I am getting any output to the battery/coil. So, when I increase the RPM's or put it under load the cylinders start missing and it eventually dies. If I remove and charge the battery seperately it will run off the battery at full power for about 30 minutes and then slowly start missing again. I have 6V at the battery (not running) and the same voltage when it is running so I am assuming that the new generator/cutout isn't working and the coil, slowly, doesn't get enough voltage to keep it running. At best I get an orange spark on the spark checker that fades when applying more throttle. it also runs longer and better if I jumper the ballast resistor so I'll have the shop check the new generator/cutout. This has really gotten to be a long process...