IH 300u problems

Hello all,

I'm looking for some initial troubleshooting guidance. I recently purchased a 5 ft brush hog to attach to my also recently purchased 1955 IH 300u. When I hooked it up for the first time I took it for a test spin through some tall grass and things quickly went sideways. I noticed almost immediately that the PTO stopped turning, but later realized that I hadn't fully engaged the lever to the latched position, so I think it was just slipping a bit. After stopping to see what was going on with the PTO, I notice smoke coming out from under the tractor only to figure out that the exhaust pipe was getting the tall grass hot.

I drove the tractor out of the grass and thought that the multiple crises had been averted only to realize that now the engine sounds like it is bogged down. It acts like it's under full load when it's sitting unloaded, just idling. It won't rev up and I have noticed a puff or two of smoke coming from under the hood near the exhaust manifold. The PTO engages and spins easily with no change in engine loading. When I try to drive the tractor it sounds like it's extremely loaded and almost kills it. It now starts hard and runs on after shutting the key off, which it never used to do.

I'm thinking that I'm going to have to tear the engine apart to see what's going on in there, but if anyone has had a similar experience and could point me in the most probable direction, I would appreciate it. The thing that has me confused is why the engine sounds overloaded. Any advice is appreciated.

This post was edited by tarment10 on 10/20/2023 at 12:29 pm.

First off DO NOT just start randomly disassembling
your engine looking for a smoking gun! For the most
part a machine has to be in running order to diagnose
a problem it is having while running.
Grab the distributor base and see if you can turn it
fairly easily by hand. If so something probably came up
against it and turned it putting the ignition out of time.
If that has happened start it up and turn it one way or
the other until you get it sounding more like it did
before. If that makes it better you will need to reset the
ignition timing. Someone can come back and cover
that process if needed.
Secondly, does the bush hog utilize the hydraulics to
raise and lower it? If so have you used the hydraulics
on this tractor before for some other purpose?
Whether or not you did you may have you inadvertently
moved a hydraulic lever off of the centered position?
The levers have 3 positions. A center where it normally
sets when no hydraulic function is required and an
activation position on either side of that. If it has been
moved to one of the activation positions this can load
the engine. Normally the lever should return to center
itself, but in this case the linkage may be stiff or the
valve has a problem. Place your hand near be do not
touch the hydraulic lines that run up on the distributor
side of the engine are they real hot? If so the lever
maybe out of place or there is some sort of
malfunction in the hydraulics. Although the hydraulics
themselves would not keep the engine from revving
up.

The brush hog is attached using the three point adapter prongs, like these https://www.yesterdaystractors.com/Farmall-300_Fasthitch-to-3-Point-Quick-Attach-Prongs_111429.html , plus a top link. I'll check the distributor and hydraulic lines, but I have raised/lowered the brush hog and didn't notice an appreciable difference in engine loading. I do know what you're saying about the hydraulics pulling the engine down some, but this is different. The distributor cap may make sense given the run-on that it's experiencing after shutting the key off.

Many like to connect ignition timing and ..run-on.. In
actuality timing has ZERO to due with the symptom of
..run on.. at least for the most part. When you shut off
the ignition there is no longer spark being sent to the
spark plugs so the ignition and or the timing it is set at
no longer plays a role in cylinder ignition. The greatest
cause of run-in is simply too high an idle speed or the
throttle plate being set at a point that does not shut off
the air entering the engine properly. This is usually
caused by the throttle plate being held open by the
idle stop to overcome a problem in the carburetor idle
circuit.
Operating your tractor longer and under load does
increase it susceptibility to run-on just by higher
engine temperatures. There is a possibility that slow
ignition timing is increasing the temperature of
combustion chamber residue like carbon which will
indeed add to the possibility of run-on.

I have a 300u. Its biggest problem is rust and junk in the gas
tank clogging the globe valve screen and carburetor. Been a
problem on and off for over 15 years.

Timing is set at TDC on #1 cylinder with the engine stopped. There is a pointer and
notch on the front pulley. The engine needs to be on the compression stroke. A way
to do that is to align the second mark that comes around with the pointer. Then look
at the rotor.unxer the cap. If it points to the #1 plug wire, that is it. If it
points to the #4 cylinder the engine needs one more rotation.
Using a simple test light, attached to ground and the smaller wire from the coil to
the distributor, set the timing by loosening the distributor so it will just turn,
turn it a half inch clockwise. Turn on the key, (the light should be off) rotate the
distributor counter clockwise just until the light comes on. That is zero degrees. C
W and CCW are looking at the distributor from the rear looking forward. Jim

Actually Jim I hate to complicate it for the original poster, but using the static timing method with a test light you can set it on TDC number 1 or the half turn off at TDC for number 4. Either way times the engine the same.

Jim said to see what post on cap the rotor pointed to when TDC mark was lined up. Unless the gears or pin that drives the distributor failed that is enough info. But that could also be a problem. Some front pulleys have up to 4 notches so TDC is the last one to pointer when turning engine in normal rotation.

My concept is based on the fact that, as he stated, it does run. thus the rotor will (more or less) point correctly to the #1 or #4 plug wire. ! Jim

Did the engine sound like it was straining before you tried out the bush hog? Did you bump one of the
hydraulic levers? If they are not centered, it will strain the hydraulic system. My 300u no longer returns
the rear lift lever to center(neutral) after the cylinder completes it's range of travel and it will
strain the engine when the hydraulics strain. I am so used to it that this does not happen very often and
only momentarily. My two remote levers still work properly and return to center. Mark.

An update for everyone, but first, thanks for all the commentary here.

I started by looking for issues in the fuel system. I took the carb off and looked to see if it was clogged up as some suggested. No issues there. cleaned a few things up, but mostly just reassembled it and put it back on the tractor.

Then I tried adjusting the advance on the firing timing. The distributor cap was set tight before I adjusted it, so it doesn't appear that it moved while I was using the tractor. I had to advance it fairly significantly though, maybe 15-20 deg., and it started running pretty smoothly. It didn't sound bogged down anymore and smoothly revved up to PTO speeds and back to a low idle. It also starts really easily now, so it looks like I'm back in business. It looks like the folks that suggested it being a timing issue were correct.

To the person that mention the run on issue was not timing related, I see your point, but when I adjusted the timing, the run-on issue completely went away, so I'm not sure what's going on there.

I'm still a little confused how loading it heavily caused the timing to get off by that much with the ignition timing set screw locked in tight, but I guess I'll take it over it being a much more serious issue.

There are still a couple issues I'm working through, namely the low idle is still too high (~800-900 rpm) even with the carb adjusted all the way down. Relatedly the tractor reaches PTO speed when the throttle is at about halfway. I'm thinking that I need to adjust the linkage arm length going to the governor using the adjustable yoke to allow full play of that arm. Separately I'm also afraid that the alternator is shot on it given the voltage on the alternator is only at about 12.2 V while running vs. 12.3 V when shut off, but that's a relatively easy fix.

Thanks again for the help everyone!

Update to the update. The troubles continue. After adjusting the timing, the tractor seemed to be running really nicely. I changed the alternator because the battery wasn't charging....and now it still doesn't charge, but that's not the issue I'm coming back to the forum for.

After the unsuccessful alternator swap out, I decided to give the brush hog another go. The tractor was running smoothly until I tried to raise the three point arms to raise the brush hog, at which point it switched back to sounding very overloaded again. This time I felt the hydraulic lines and they were starting to warm up. I think that there may be an issue with the hydraulic control valve on the right side of the tractor seat. It leaks pretty badly, so I'm wondering if there is something jammed up in its internals. The hydraulic pump where the ignition housing bolts in is also in need of a software replacement, which I'm planning on doing and have the parts for. I'm wondering if ignition housing is also getting overloaded with hydraulic oil because of the high load of that control valve locking up forcing more oil to leak from the pump seals.

What I could use from this forum is some advice if you all think that the problem could lie in components other than the pump and that control valve. I'm planning on servicing both of them today.

Hopefully a final update here. I figured out what the issue is and I'm pretty sure I fixed it. Just wanted to post on here in case anyone else runs into the same issue.

To recap, the tractor's ignition timing was changing for seemingly inexplicable reasons. I first noticed it while attempting to brush hog a field shortly after buying the tractor. I fixed the timing and then went to hook up to the brush hog again, but this time the engine started running poorly the instant the lift arms came under load.

Since the hydraulic pump was already pretty leaky, I decided to take it apart and refresh the software, hoping that I might stumble across the cause of my troubles. Almost immediately upon taking the pump off I found my issue. The screw that holds on the coupling between the pump and the ignition unit was twisted off. I thought that was weird since it shouldn't be under much load. Upon closer examination, I saw that the tiny halfmoon key that is suppose to lock the coupling in place was sitting underneath the coupling itself. It appears that someone before me tried to service the pump, but must have knocked the key out while putting the coupler back together and didn't notice.

So what was happening was the hydraulics would come under load when I would use the lift cylinder in the back, which would in turn cause a small amount of slippage between the coupling and the pump output shaft. That would cause the timing to be off. No idea how it continued to run like that.

Regardless, I think I have it fixed. I was able to start it up and have it running smoothly. I'm going to try to use it with the brush hog tomorrow if the weather is nice. I hope someone learned something from my story because I certainly did.