I don't know specifically for an 8440, I don't have a tractor that big, but what you're looking for is a "Cold Start Kit". It does exactly that, bypasses all hydraulic flow until the engine is started. On smaller tractors, there is a poppet you can screw in manually that does this, then you have to turn it back out when started. I wouldn't know where to tell you it is, if it is, on that tractor, sorry.
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