Re: Farmall 400 backfiring and dying

Posted by Bob M on March 05, 2007 at 09:13:53 from (151.190.254.108):

In Reply to: Farmall 400 backfiring and dying posted by Duanes on March 05, 2007 at 08:33:36:

Could be fuel starvation. Try partially pulling the choke when it begins to falter. If the engine picks up again fuel starvation is the problem. Look for a plugged strainer in the sediment bulb, junk in the bottom of the tank, a plugged gas cap vent, etc

If the choke thing doesn't help most likely the coil is failing. It works OK cold, but as it heats up it's output voltage tails off, causing the engine to first misfire and then quit altogether.

Try running it again. When it falters immediately shut it down. Now pull the center wire from the distributor and attach it to a good spark. Lay the plug on top of the distbutor and crank the engine with ignition switch "on". You should see a hot, blue spark at the plug. However if the spark's a lazy yellow, suspect a bad coil.

Also check the coil temperature by hand after it's been running a few minutes . If it's noticably warm to the touch it's probably the old 6 volt coil and you are now feeding directly from it 12 volts. You need to add a ballast resistor in the primary circuit to knock the voltage down to 6 volts to keep it from overheating (and also keep the points from burning out prematurely)

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Incidentally from your description it sounds
like your ammeter is wired up wrong. Turning on the lights should not change the ammeter reading or only cause it to indicate LESS charge.

Try turning on the lights the the engine stopped. A correctly wire ammeter will show 5 - 10 amps of DISCHARGE with the lights on.

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