Re: tractor running rough on cold starts

Posted by dick on November 03, 2002 at 10:03:29 from (209.245.9.32):

In Reply to: tractor running rough on cold starts posted by jimbo on November 03, 2002 at 06:48:47:

I agree with Hugh and redhead, your expectations are rather unrealistic. Let's remember what we're dealing with here, a governor-controlled carbureted fuel system.

Most (all?) new cars these days have fuel injection, where gasoline is sprayed directly into the cylinders, which warm up almost instantaneously. Your 400 starts with a cold intake manifold which tends to condense what gasoline the stone-cold carburetor manages to vaporize until it (and the carb.) get warmed up. Even joined to the exhaust manifold this takes a while, and during that time the engine is going to see fuel/air mixtures (and moisture contents) which vary all over the place as liquid gasoline and water condensed (or frozen) on the walls of the intake manifold vaporizes at a very non-uniform rate. It's no wonder the engine isn't very happy while this is going on. Take a look at your carburetor and intake manifold, you may actually see ice on them this time of year until the engine warms up.

On an old carbureted automobile, one has (had) the option of doing the pump-the-gas-pedal technique to get moving a bit quicker. Not an option with a governor.

Something which probably affects warmup in many of these old tractors is replacement of the original thermostat with the cheaper automotive variety. The original was designed (at least in my 300U) to recirculate everything through the engine until the engine warms up enough to open it. Using the typical automotive thermostat means the water pump is dead-headed and no circulation takes place until enough heat (somehow) reaches the thermostat to open it. Not a very efficient way of warming things up.

Another way to look at it is that cold-weather starting is one of the ways your tractor expresses its individual personality. The technique (choke and throttle settings, how long to crank, etc.) which works best varies widely among these old beasts, depending upon engine condition, etc. Personally, I get a kick out of seeing a 40- or 50-year-old original tractor engine start, even in cold weather. How many automobile engines that age still run, even under ideal conditions?

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