My 300 Farmall starts great, runs fine at idle but when I try to accelerate it sputters and dies. I suspect it is because the battery is low on charge. I haven't run it at all over the winter and I can see the ammeter peg to the right when I increase the throttle, at least until it dies. Took the battery out and it is charging about 10 amps. Any other suggestions or do you think this will solve the problem? The only other thing that has changed is I installed a new coil, before I put it up for the winter.
- Thread starter Ksfarmmer
- Start date
Charge the battery and reinstall the old coil to see if that fixes the problem. If it doesn't check your fuel system for blockage. When it quits running check for fire to your plugs before it has a chance to cool. If you still have fire
its not the battery or coil. If there's no fire replace the condenser. Hal
its not the battery or coil. If there's no fire replace the condenser. Hal
Janicholson
Well-known Member
Ignition systems use less power when running fast than at idle (more voltage is required to jump a partial vacuum than when it is filled with more air/fuel mix) thus the problem is far more likely to be a fuel supply, or carb issue (possibly main jet leanness or plugged up port from sitting. JimN
Anonymous-0
Well-known Member
The ignition system never sees a "partial vacuum." There is always pressure in the combustion chamber except perhaps under extreme deceleration. He complains of sputtering on acceleration. That is when voltage requirements are the hightest. Watch the voltage spikes on a scope when you quickly open the throttle.
Janicholson
Well-known Member
Well, with respect, The spark plasma has a tougher time getting through the (to avoid issues with an actual unknown) far lesser molecules in the Idle combustion chamber, than the high pressure fuel and air in the open carb situation. I have been looking at Sun and Allen ignition scopes since 1960. Idle has highest spark voltage demand, wide open, maximum HP at rated speed and has least. Jim
Anonymous-0
Well-known Member
Dear Jim,
I am sorry, but it just doesn't work that way. Don't you remember the old Champion sparkplug testers that you hooked up to compressed air and then looked through a little window to see if it fired? Remember the old saying that the plug won't fire under compression. Granted that the plugs might require more voltage at idle than cruise, but acceleration is a different story as the voltage spikes go way up under "snap" acceleration. Air has a lot of resistance and compressed air even more. That is why cars will idle ok, but miss under load. When voltage required exceeds voltage available, you have a miss.
I am sorry, but it just doesn't work that way. Don't you remember the old Champion sparkplug testers that you hooked up to compressed air and then looked through a little window to see if it fired? Remember the old saying that the plug won't fire under compression. Granted that the plugs might require more voltage at idle than cruise, but acceleration is a different story as the voltage spikes go way up under "snap" acceleration. Air has a lot of resistance and compressed air even more. That is why cars will idle ok, but miss under load. When voltage required exceeds voltage available, you have a miss.
Janicholson
Well-known Member
Well we will end up disagreeing to a degree. The fowled plug will misfire under load because the fouling and compressed air are making that track more conductive. All four of them at once is not the problem this tractor has. (Opinion) JimN
Make sure the voltage of new coil you installed matches the voltage of your tractor's system, if you haven't already. The spark from a 12 volt coil will be pretty weak on 6 volts. The engine might start, but will quit when a fog of gas hits the plug when you open the throttle. If your charging system is working, which it sounds like it is, that alone is enough to keep the engine running OK.
There is a lot we dont know here but, if that battery was strong enough to start the tractor-several times- then the battery and the gen is way strong enough to run it at fast idle.
IF the tractor was running smooth when stored then my money goes on too lean a mixture caused by any number of problems.
Dell
IF the tractor was running smooth when stored then my money goes on too lean a mixture caused by any number of problems.
Dell
Janicholson
Well-known Member
My neighbor just asked me to help him get a Evinrude 6hp twin fishing motor running (again).
It primed up and started on one cylinder. When opened up (and as it accelerated) it would run on 2.
if throttled back at all it quit firing on that cylinder. I switched plugs from 1 to 2. the misfire went with the plug. I put in a new plug issue gone. Some will fowl and misfire when at idle, and some will misfire under load. I've seen every possible combination. Jim
It primed up and started on one cylinder. When opened up (and as it accelerated) it would run on 2.
if throttled back at all it quit firing on that cylinder. I switched plugs from 1 to 2. the misfire went with the plug. I put in a new plug issue gone. Some will fowl and misfire when at idle, and some will misfire under load. I've seen every possible combination. Jim
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