IH 656 Running Poorly When Warm

[Irish_Jake]

Hey all - I have a new to me '67 IH 656 that's having issues running after it warms up. Tractor has a gas engine, some blow-by/oil burning (but not excessive) and starts up and runs initially great. After running for 30-45 minutes however I lose all power, can't rev up the engine, and it starts bogging down and dying. It will start back up after dying completely, and stopping + pushing in the foot-n-inch pedal seems to help bring the revs back up. It will also run better downhill than uphill when this happens, so load seems to be an issue.

I bought the tractor with a dead alternator and nearly dead battery, and so far my only work on it has been replacing those. Below is a video showing operation after about 40 minutes of running, no heavy work yet though mostly idling. Aftermarket temp gauge shows the tractor was up to 180*, so not particularly hot.

My voice isn't coming through great on the video, but I've repeated everything said there here, and it will give a good view of what I'm hearing and seeing.

https://www.youtube.com/watch?v=UiXEFM9mgxw

 

[Janicholson]

90% of that described problem is associated with ignition problems. Most often it is a internally shorted coil. The short
happens over extended time from repeated heat cool cycles (normal running heat, and normal ambient temperature) cause
insulation to rub off between turns of the primary winding inside. As the windings touch one another, the coil begins to have
less and less resistance. This causes it to begin drawing more and more current. The current causes heat (like a toaster)
the heat causes spark failure. If when it begins to falter, you feel the coil (with it shut off) and find it to be extremely
hot. That is likely the problem. Replacing it with a coil designed for tractors with a ballast resistor is correct. It
does not need to be an IH coil. Unless it has been rewired that will be correct. If the coil is kinda normal (pretty warm,
but touchable) there are other issues as well from a worn distributor shaft, to bad condenser, to fuel delivery problems.
Jim

 

[Irish_Jake]

(quoted from post at 12:57:49 07/05/21) Thanks Jim, that's straightforward to check out so I'll give it a check when I run the tractor next.

 

[Irish_Jake]

(quoted from post at 12:57:49 07/05/21) 90% of that described problem is associated with ignition problems. Most often it is a internally shorted coil. The short
happens over extended time from repeated heat cool cycles (normal running heat, and normal ambient temperature) cause
insulation to rub off between turns of the primary winding inside. As the windings touch one another, the coil begins to have
less and less resistance. This causes it to begin drawing more and more current. The current causes heat (like a toaster)
the heat causes spark failure. If when it begins to falter, you feel the coil (with it shut off) and find it to be extremely
hot. That is likely the problem. Replacing it with a coil designed for tractors with a ballast resistor is correct. It
does not need to be an IH coil. Unless it has been rewired that will be correct. If the coil is kinda normal (pretty warm,
but touchable) there are other issues as well from a worn distributor shaft, to bad condenser, to fuel delivery problems.
Jim

Just tested this, and the coil is hot but not so hot that I can't hold my hand on it indefinitely, so that doesn't seem like what you're describing.

I can bring the revs back up by working the choke a bit when it's dying, so that may point to a fuel issue of some sort? I also noticed that the amp light sometimes dimly flashes when the issue is occuring, but that points back to electrics.

Thoughts?

 

[Janicholson]

slightly richer mixture is easier to ignite, so a failing ignition would be hidden by that as well. To check fuel supply, engine off, take a clean
coffee can and (with the sediment bowl valve turned on) open the carb drain at the bottom of the carb. It should run a pint or so a minute. It should
start out fast, then slow down some, but a nice steady stream like a soda straw, should continue for at least a minute. If the supply is Ok there
still could be plugged metering holes/jets in the carb. If the fuel checks out, replace the condenser and set the clean points to .020 when they are
as open as the dist. cam will push them. Jim

 

[fixerupper]

Jim is on the right track. With some cylinders cutting in and out like that weak spark is definitely the culprit. If it was running lean the engine would spit and sputter more.

 

[Irish_Jake]

(quoted from post at 09:29:37 07/07/21) Jim is on the right track. With some cylinders cutting in and out like that weak spark is definitely the culprit. If it was running lean the engine would spit and sputter more.

Got it, thanks guys. I'm going to check the gas flow next time I'm at the tractor later this week, but I also went ahead and bought an ignition tune-up kit (includes condensor) and a coil. For $40 shipped it's easiest to just hit the likely problems. If it's not that or the points, or the carb isn't flowing fuel correctly, I'll pull the carb and give it a good cleaning.

 

[Irish_Jake]

Some part of that system ended up being the issue - swapped out the rotor, coil and condensor and the issue has gone away. Thanks for the help!