More H Troubleshooting

Hi All,

I posted a couple weeks ago with problems my dad (retired) and I are having getting a 1950 H with magneto running properly. Thought it was timing, but we timed the pinion gear to the rotor gear, and timed the magneto gear to the cam gear so that the impulse coupling snaps at TDC on the compression stroke. Wires set for 1-3-4-2 firing order. Carb has been rebuilt by a "professional". Even took it back to him when we had problems starting and running tractor (see below) and told him to check it again. He said it was fine.

I don't think it is the timing, because it will start and run fine for 10 - 15 seconds then "sputter" once or twice (but not die), then run fine, then sputter once or twice (at about 10 second intervals). No back fires or anything, just sputters a little bit every 10 seconds or so. In between "sputters" it sounds perfect. It will run like this as long as you let it with throttle above idle. My thought is that there must be plenty of revolutions in those intervals such that if the timing was off, you couldn't have it run so well for even short periods.

We have to pull the choke for just a second when starting to get it to fire, then we have to keep the choke on just a *hair* (hardly at all) to keep it running. I never have to choke my own H, even when it is cold, but I know that varies between tractors.

Tractor will not stay running when throttle is set to idle. We have to keep it at 1/4 to half throttle to keep it running.

If you turn off the engine and try to restart, it won't, and the carb floods. We have to wait til it sits a long while (usu. overnight) before we can get it to start again.

Questions:

This just sounds like a carb problem to me, but

1) Could it still be a timing problem?
2) if it's the carb, what do we do / check - we have already set the idle and jet screws to IH manual specifications and even played with them while running with no success. And presumably the carb has been "re-built".
3) Even though the magneto was rebuilt with new coil and condensor and points (and presumably re-charged magnet), could a faulty coil or condensor cause these symptoms?
4) Would the governor have anything to do with the symptoms we are experiencing?

I'm at a loss. I've never had this kind of difficulty with an old farmall before (but I have never had one with a mag, either).

Any thoughts would be GREATLY appreciated. Thanks!

The likely hood is a manifold leak. Either at the head, at the carb, or internally between the Exhaust and intake where they touch.

While it runs, take a propane torch (with the tip taken off so only propane comes out) and with it turned on just a little, move it all around the intake system. (do this outside, and have good sparkplug wires) If there is a leak, the engine will pick up speed and run correctly! If none, (and you are sure the carb is correct!!!) then pulling the manifold to check for an internal crack is needed. Jim

If Jim's solution doesn't help, it is still a blocked idle passage in the carb. Those cast iron carbs are like the 2 cyl JD's & have rust that needs to be drilled out.

If all else fails,take the carb off your H and try

jimmy

I'd agree with that. If it's running with it choked, even just choked a little, it's not getting enough gas in the air fuel mixture.

"enough gas" is a relative thing. Relative to the amount of air getting into the cylinders.

IF the carb really is "ok", and it only runs while choked - then it's most likely getting extra air into the mixture, thereby lowering the amount of gas to air in the fule/air ratio - and that could only be from an air leak.

.. but it REALLY sounds like blockage in the carb.

I'd agree with that. If it's running with it choked, even just choked a little, it's not getting enough gas in the air fuel mixture.

"enough gas" is a relative thing. Relative to the amount of air getting into the cylinders.

IF the carb really is "ok", and it only runs while choked - then it's most likely getting extra air into the mixture, thereby lowering the amount of gas to air in the fule/air ratio - and that could only be from an air leak.

.. but it REALLY sounds like blockage in the carb.

Hold your hand over the throat of the carburetor while a helper try's to make an engine start. If there's not much suction on your hand is an indication of low manifold vacuum. Make sure your intake manifold is tight. Open your main jet adjusting screw near the bottom of the carb.
I would check the flow of gas from your tank to the carb. If there's good flow from the tank remove the tube fitting where your gas line connects and check for a plugged screen behind that fitting. If none of this helps remove that main jet adjusting screw and blow out the jet with air pressure. Hal

The new condenser COULD be at fault yet.

(quoted from post at 04:18:43 10/19/11) Hold your hand over the throat of the carburetor while a helper try's to make an engine start. If there's not much suction on your hand is an indication of low manifold vacuum. Make sure your intake manifold is tight. Open your main jet adjusting screw near the bottom of the carb.
I would check the flow of gas from your tank to the carb. If there's good flow from the tank remove the tube fitting where your gas line connects and check for a plugged screen behind that fitting. If none of this helps remove that main jet adjusting screw and blow out the jet with air pressure. Hal

Click to expand...

Please use some caution when holding your hand over the carburetor intake. If the engine is good and strong, with GOOD compression, the vaccuum will try to pull your hand right on into the engine, and at best you will end up with a sore hand. We won't talk about the worst case scenario.

Do you have any documentation for this Rusty? I
thought the most vacuum you would ever have is about
15 lbs? Anyway I've choked lots of engines with my
hand and never been hurt by it.

(quoted from post at 06:00:46 10/19/11) Do you have any documentation for this Rusty? I
thought the most vacuum you would ever have is about
15 lbs? Anyway I've choked lots of engines with my
hand and never been hurt by it.

Click to expand...

Yes, on a super H. The ignition switch was on, and the engine actually started while my hand was covering the intake. If the engine had not died quickly, my hand might still be there.

Thank you everybody for your extremely helpful comments. Yous guys are brilliant. Most people I ask end up telling me to do and check things I have already done. You guys have some methods I would never have come up with. Thanks again. If I get it figured out, I'll try to remember and post the solution FYI and for the archives.

That's about 15 pounds per square inch! and it adds up fast. Be careful.

That's the way we checked a vehicle when they used mechanical fuel pumps. You could keep the engine running by keeping your hand over the throat of the carb. Never had any issues with my hands by doing this. Hal