Farmall H backfiring

[Tucker474]

I have owned my Farmall H for around five years. It was re-
done before I bought it. Recently it started to backfire and
shut off. It would restart but randomly do this. Progressively
it got worse where it doesnt restart very easily. I am in the
process of cleaning the carb. The fuel line and filter all seem
OK. Any thoughts or suggestions?

 

[Michael Soldan]

Backfire or misfire is often a timing issue or excess air . Check timing and wires t see if there are any issues there , and then go over carb settings and air intake chambers

 

[Tucker474]

Timing wouldnt change on its own correct ? I did check/wiggling the wiring to plugs and distributor cap while it was idling and it didnt change anything. When you reference air intake chambers, you mean the manifold correct not the air cleaner pipe ?

 

[redforlife]

Does it run ok at start up, and then start to 'NOT' run right, then back fires, and then dies?? Only doing the backfiring after it starts not running right?

Or does it kind of not ever run right, backfires all the time, and dies once in a awhile??

Because this could change up the diagnosing a little bit. Mean different things.

If it backfires all the time, even on a cold start, it could be something like a cracked distributor cap, valve or valves sticking open, a couple spark plug wires crossed up. Just to name a few.

But if it runs OK at cold start up, and the not running right and backfiring comes on later, perhaps even after warm up, it changes things. Then it could be a problem with fuel flow to carb, a bad coil or condenser, a bad 12 to 6 reducer to dustributor (if 12v converted), and this list likewise goes on.

If you or nobody else has 'NOT' done any recent work to this thing, as in, it has just set for a lengthy spell and now the problems but was OK before, you can rule out things like timing, carb settings, and things like that. Adjustment type stuff.

Points are bad about corroding on a tractor that just sits. But this would create a possible mis upon start up and subject to do it all the time. It wouldn't cause a backfire until tractor got good and warmed up, and unburnt intake mixture was shoved into the now hot exhaust after a miss. Problem might not, and likely not, be just limited to one cylinder if you got a points problem. If you can even get it to run. But clean or replace points if this sounds like your problem. Might be a good idea to clean them regardless.

Your doing the right thing by 'cleaning' the carb, instead of rebuilding it!!!! Thumbs up to that. But if you change, or already did change the carb settings, you'll have to get those set back to pretty close, and then fine tune on tractor with it running.

 

[used red MN]

Hello Tucker welcome to YT! I would say your problem is more likely the ignition condenser or a coil problem. Hopefully you can obtain a good replacement condenser.
These days it seems like it is difficult to get a good one that will last. Although I doubt it is directly related to your problem it is a good idea to check the mechanical advance in the distributor to make sure it is free. Since you are working on the carburetor I just want to make sure you aware that in the fitting where the fuel line attaches to the carburetor is a fine screen. Make sure you remove the fitting and clean the screen. Also checking the valve clearance and a compression check are also good things to do.
I also believe ..intake chambers.. mentioned by the other poster refers to the intake manifold, must be a European term, never heard of it though.

 

[Fritz Maurer]

Id pull the plugs and see whats going on inside the motor. Soot fouled plugs can cause backfires.

 

[Michael Soldan]

Mice and birds have been known to pack the air cleaner. Timing could change and move slightly ahead or behind. The easiest thing you can do right now is flip the distributor cap over and spray it with WD40 , this will take any moisture out of the cap , then try to run the tractor. A bad coil has the symptom of running well when cold but when it gets hot it fails , is this happening? Also a tractor that sits could have corrosion on the distributor tips so the rotor isn't making contact all the time. You will figure this out , some good ideas on here, let us know how you make out..good luck. I have two H's and an M. The M was backfiring and discovered the cows had pulled some wiring off and I guessed wrong so went through the firing order and got it right.

 

[rustred]

As soon as it stops check to see what kind of spark u have. Plus feel the coil, if its hot that your problem. Carburators do not cause a backfire ! Its a timing or burnt valve issue or valve setting.

 

[K-Mo]

Yes, timing can change on it's own. I've seen it more than once when the pin on the distributor gear shears.
The pin shears, then the gear slips and catches at a different position.
Check the timing.