Low Immediately after Start

Mon Sep 23, 2013 7:36 am

I own a 1951 Super A and a 1958 Cub. Both have hydraulics. Both run well. I was wondering if someone could explain why these units have such low power when first started. After about a minute of warming-up, they're fine. I live in the cold north, along the south shore of Lake Erie, where temperatures in my storage building can dip into the 20'sF in the depths of winter. At this time of the year, my tractors may be 60F just before starting them. Immediately after starting, they're weak. Is this because of the power necessary to begin warming the hydraulic fluid or is this only part of the problem? Carburetion may be another part of this puzzle. Is their anything I can do to improve this situation?

To give some relative measure of weakness, my tractors nearly stall if their clutches are depressed immediately after a cold start. The torque load on the throw-out bearing is nearly enough to stall the engines. If I choke the engines after they start, they can carry the clutch throw-out bearing torque (transmission not in gear nor any other engine loads).

Re: Low Immediately after Start

Mon Sep 23, 2013 8:15 am

http://www.mytractorforum.com/archive/i ... 22743.html

Discussion on topic, above.

Let the tractors warm up a bit before operation. Engine tune up may help, a bit. In very cold temperatures you could shutter part of the radiator to raise the coolant temperature.

My Cub with Zenith carburetor is much more touchy immediately after start up than the Cub with an IH carburetor. Cub with Zenith carb runs fine after a couple minute warm up.

Re: Low Immediately after Start

Mon Sep 23, 2013 9:03 am

John:

One thing I have learned about older tractors living up here is that one should never attempt to operate a tractor immediately after starting. I always let them warm up at least a couple minutes in the summer and longer in winter. If not something could possibly break ... and that isn't desirable. Until the engines warm up the hydraulics are not going to work very well either as they depend on a well idling engine. So a stuttering engine just warming up is going to be bogged down and possibly stalled simply because of the load placed on it by activating the hydraulics or trying to engage the clutch. The carburetion may be a factor if there is a lot of humidity or condensation on the carbs. I have seen this phenomenon even in the bitter cold of winter where moisture has shut the Cub down. A good tuneup would probably be a good idea as Eugene suggested, there is no down side to that.

I keep my Cubs in my pole barn. It is unheated but well insulated and has a lot of southern facing windows that helps keep the Cubs warmer. So when it comes time to start them it doesn't take as long to warm the engines up, but they still have to idle before use to get the engine running smoothly. I would think something like a windbreaker would also help to keep the heat in and the Cubs warmer .. it would probably have to be a fabrication project though.

Re: Low Immediately after Start

Mon Sep 23, 2013 9:20 am

I agree with the tune-up suggestions. But it is completely normal for a carbureted engine to need some choke when first started, it needs more when it is colder. You can't expect to flip the choke wide open as soon as the engine starts.

Re: Low Immediately after Start

Mon Sep 23, 2013 11:20 am

Cold engines are extremely inefficient.

They have lower compression than when at their normal operating temperature. Lots more friction when cold. Lubricants are very thick. Gasoline doesn't vaporize well when the droplets travel into a cold combustion chamber. Liquid droplets will not burn, only the vapors - thus the need for a choke to reduce air intake into a cold engine. So give these old engines a little time to heat up; so the metal components can expand to their intended size, lubricants can lose excessive viscosity so they pump easily and fuel can vaporize efficiently in order to reach it's maximum explosive potential.

Re: Low Immediately after Start

Mon Sep 23, 2013 10:06 pm

Ironlegs, I am assuming it has been a long time since you drove an engine with a carburetor rather than computerized fuel injection. The computerized injection systems automatically adjust timing and fuel to compensate for temperature both of air and engine. On a cub or any other engine with a manual choke it is necessary to use the choke frequently to start or to have enough power to do anything until the engine warms up.

Re: Low Immediately after Start

Tue Sep 24, 2013 4:13 am

One more thing to consider; if you notice that your mower deck, or other implement drops while your cub sits the internal hydraulics may be allowing some fluid bipass. IMO that can rob some power at start up to get back to the set position of the control. Other cub experts will surely chime in if they agree or disagree with this statement.
Dave

Re: Low Immediately after Start

Tue Sep 24, 2013 8:44 am

Groove Critter wrote:One more thing to consider; if you notice that your mower deck, or other implement drops while your cub sits the internal hydraulics may be allowing some fluid bipass. IMO that can rob some power at start up to get back to the set position of the control.

I've seen the extra load from that situation make them harder to start. I've certainly stalled cold engines by moving a Touch-Control lever. But the extra load it causes usually won't last as long as the minute or so Ironlegs described.

This does suggest a closely related situation that could be a factor. Each Touch-Control lever has a stop at each end to keep the system from loading up under pressure at the end of the stroke. If a stop is not adjusted right, a cold engine could have more trouble working against the extra load.