Farmall C jumping timing under load

[DavidDavis]

I’ve had this farmall C for 52 years and all of a sudden it jumps timing. Once I shut it down it backfire when trying to start it. I found I have to get #1cylinder TDC then move each plug wire one position and she fires right up. The distributor is not moving. I can move distributor shaft r-l 3/8” I can move the next shaft to right 1/8” and the slotted drive shaft from governor at least 1/4”. Do I need new bushings/spacers for everything? Am I missing something? Is there a kit to fix this?

 

[used red MN]

I’ve had this farmall C for 52 years and all of a sudden it jumps timing. Once I shut it down it backfire when trying to start it. I found I have to get #1cylinder TDC then move each plug wire one position and she fires right up. The distributor is not moving. I can move distributor shaft r-l 3/8” I can move the next shaft to right 1/8” and the slotted drive shaft from governor at least 1/4”. Do I need new bushings/spacers for everything? Am I missing something? Is there a kit to fix this?

Hello David, welcome to YT! Photos of what you are talking about as far as what you are specifying as “movements” i.e. 3/8”?? Maybe we can talk through it a bit. The distributor on your C mounts with its shaft horizontally along the engine. You say you can move the shaft 3/8” right to left, is this end play moving the shaft forward and back? Or is it side play such as you grab the points cam and it moves towards the engine and away from the engine that 3/8 of an inch? Or are you talking in terms of rotation slack that it turns free back and forth at that measured limit?

 

[DaveBN]

If you move the spark plug wires and it then runs ok someone is playing a trick on you. It would be an incredible coincidence if the timing changed EXACTLY that much.
Dave

 

[DavidDavis]

Hello David, welcome to YT! Photos of what you are talking about as far as what you are specifying as “movements” i.e. 3/8”?? Maybe we can talk through it a bit. The distributor on your C mounts with its shaft horizontally along the engine. You say you can move the shaft 3/8” right to left, is this end play moving the shaft forward and back? Or is it side play such as you grab the points cam and it moves towards the engine and away from the engine that 3/8 of an inch? Or are you talking in terms of rotation slack that it turns free back and forth at that measured limit?

It slides in and out, r-l 3/8
It could be normal play but I need to confirm
There is no side play or wobbling
It does not move toward or away from the engine

 

[used red MN]

It slides in and out, r-l 3/8
It could be normal play but I need to confirm
There is no side play or wobbling
It does not move toward or away from the engine

Does the mechanical advance in the distributor work? Twist the rotor clockwise with your thumb and forefinger. It should twist against spring tension with the tip of the rotor rotating a 1/4” or more and then spring back when released. The points cam (15 in linked diagram) turns on the actual distributor shaft when the advance weights act on it. It may be floating on there and giving you some of the end play. I can’t remember what holds it on the shaft, some have a small snap ring on the end. It may also just use the tension of the advance springs to hold it in position.
CNHI Farmall C dist. diagram

 

[BarnyardEngineering]

What does "r-1 3/8" mean? Does that mean 1-3/8", one-and-three-eights inches? That's a LOT.

These engines don't "jump timing" unless something really really bad is happening within the engine. Pretty much the only way they can jump time is if there are teeth missing off a gear. That would not cause the engine to jump exactly one position on the distributor, though.

Has it done this jump-exactly-one-position-on-the-distributor more than once? How often does it happen? I also find it odd that it jumps exactly one position on the distributor.

Let's clarify. The tractor is running FINE when you shut it off, but the next time you go to start it up, it has jumped one position on the distributor? Is that immediately after you shut the tractor off, or hours/days later?

Your answers will help reduce the number of possibilities here. Otherwise someone's playing a joke on you, or you're playing a joke on us...

 

[DavidDavis]

Right to left 3/8 of an inch
I do not use the tractor every week but this has happened 5 or 6 times over the last five years
It happens when I pull a steep hill or hauling heavy load. I’ve gotten so used to finding cylinder one TDC and moving the plug wires to reset the distributor. I’m thinking there is a lot of play in the governor and under load the distributor is disengaged in the governor slot. Sitting idle the governor shaft slides in and out at least 1/4 of an inch. If I were a betting man I would say the governor needs rebuilt.

 

[560Dennis]

Just a suggestion, this old post on YT might help you with this problem.

https://www.yesterdaystractors.com/cgi-bin/viewit.cgi?bd=farmall&th=379140

 

[grandpa Love]

Right to left 3/8 of an inch
I do not use the tractor every week but this has happened 5 or 6 times over the last five years
It happens when I pull a steep hill or hauling heavy load. I’ve gotten so used to finding cylinder one TDC and moving the plug wires to reset the distributor. I’m thinking there is a lot of play in the governor and under load the distributor is disengaged in the governor slot. Sitting idle the governor shaft slides in and out at least 1/4 of an inch. If I were a betting man I would say the governor needs rebuilt.

Here's a very slim possibility......there is a spring loaded spacer in the governor. It comes out of the center and pushes against the cover. If that spring is stuck compressed all the way in the governor could possibly move forward enough to disengage the distributor drive. Again,slim chance,but possible. Easy enough to remove the governor case and check.......out of hundreds of Farmalls we have had this happen once, one B would not stay timed, drove us crazy, found this issue,freed up the spring no more issues. We now remove, clean, inspect and repair the governor on every tractor.

 

[BarnyardEngineering]

Okay thanks for the clarification. Even 1/4" and 3/8" is a lot of movement. Indeed an interesting theory of the slotted shaft disengaging, because that indeed would put the distributor exactly X posts off depending on how many half-revolutions it was disengaged for.

Really if it's that loose I would be looking for another complete distributor in better shape.

 

[used red MN]

Here's a very slim possibility......there is a spring loaded spacer in the governor. It comes out of the center and pushes against the cover. If that spring is stuck compressed all the way in the governor could possibly move forward enough to disengage the distributor drive. Again,slim chance,but possible. Easy enough to remove the governor case and check.......out of hundreds of Farmalls we have had this happen once, one B would not stay timed, drove us crazy, found this issue,freed up the spring no more issues. We now remove, clean, inspect and repair the governor on every tractor.

Sounds like you might take the “win” on this one! One kudo allotted. Hey, rr is gone so now you got one less guy to run you off the rails.

 

[Powered By IH]

Sounds like you might take the “win” on this one! One kudo allotted. Hey, rr is gone so now you got one less guy to run you off the rails.

Gone now? Can't post or what?

 

[used red MN]

Gone now? Can't post or what?

Oops, let the cat out of the bag. Taking the 5th. For reference