Farmall H only runs smooth on all four under load

Working out another bug on my 43 H.

Some times when i cold start the tractor it seems to idle smooth. but then it gets to popping and carrying on. Almost like its firing before or after where it should on some cylinders. No RPM is any better unless you apply some sort of load. When you put the tractor in a high gear it runs smooths and picks off all four cylinder nicely until the load goes away. You can then slow the engine RPM down and then increase it again and it will run smooth until the engine catches up to the speed setting.

Things I've tried to correct the issue.

I had been thinking it may be distributor issues as I thought it had rotational slop on the button/rotor. I checked my other H I have for the same slop in the distributor and that one had the same amount of free play. That tractor runs perfect.

I had to set the timing by ear. There are NO timing marks that I can see on the crank pulley. I spent a bunch of time staring at it and rotating and so has another person. The timing I set it to appears to be ok, and no adjustment makes it run better. Carb settings appear to be ok as well.

I got a points/condenser kit from TSC and put that in the distributor. A new Rotor came with the kit. I didn't get a new cap for it yet as they didn't have one. I hadn't thought about trying the one off my good running H till just now so I will try that next.

I need to get a new set of plugs for it. I have no idea on the age of them and one of them wasn't working properly so I switched it out for the only new spare I had lying around which got that cylinder firing again. I probably should get a set of wires too as they are original IH. (They are marked on the boots at the distributor with IH) I did however change them out for the wires off my other H and it made no difference so I don't think that is part of the problem.

Thanks for any help.

others will have better thoughts than I do on this but from what you are describing, it sounds like too much fuel all the time unless you have it under load when it will take all the fuel it can get. is it a carb setting? governor not set correctly? both can alter fuel into the motor.

I would put a timing light on it at idle and see if the timing is jumping around, otherwise it sounds like an idle mixture issue.

A note on the timing, you do not need to know the marks, just see if the timing is steady and not jumping around.

I time mine by ear, full throttle, adjust for peak RPM, then I back it off a "little" bit if the idle is rough.

Vacuum leak

Ok, I'll mark the pully with some chalk and put a light on it. I hadn't though about. That should tell me if something is out of wack on where its firing.

Say it was bouncing about. What could be causing that?

I have to double check again but when I was checking on rotational play on the distributor, it felt as if there was more springy-ness to the tractor i have that runs right compared to this one.

Timing bouncing would be caused by worn bushings, broken springs, or sticky/worn weights.

That is a good point, squirt a little brake clean on mating surfaces.

Weak valve spring? Bad
condenser? Have not had good
luck with new ones, as also
seems to be the general
consensus. Just a thought I
guess.

Ross

That engine has a siamese manifold, which means 1&2 share a runner, 3&4 share a runner, so it will run lean on a pair of cylinders if there is an intake leak.

I had two H distributor drives apart this year where the timing gear was slightly loose and working back and forth. One wore out the keyway in the gear and the other wore out the key. Again this is the part the distributor bolts to. Just something to check.

cracked intake manifold?
caseman-d

I was going to diagnose that last night by spraying some brake clean at the manifold flanges. unfortunatly I never got it started. It fires a little but never enough. I'm going to stop for new spark plugs tonight. They seem rather weak

Well got it running again last night guess the better plugs made a difference on starting. Sure enough the gasket on cylinders 3 and 4 is bad. I can spray starter fluid at it and it will start to slow then pick and run great, then get goofy again. Hopefully I can get gaskets for it tomorrow.

Looks like you found your problem, I wanted to comment that running better under load is hardly ever bad plugs, wires, or any other contributor to a weak spark. Anything in the distributor gear train can cause the problem, as well as a minor vacuum leak. Most of mine bounce around idling but I really don't care if they get down and pull when asked to.

Glad you found it, a lot of people forget about intake sharing between cylinders.