Believe it or not, Greg, you can do this and it can occur quite easily. I've done it several times, especially when the vehicle has one, or more than one, bad glow plug.

I've tried to start the 617, in the old 123, at 25 degees with the typical 1/2 pedal and it would try to fire on one or more than one cylinder but would never climb that curve up to finally running on its own. I already knew that I had a glow problem with it.

So, I let it sit a minute or two and tried to start it with no pedal at all. It cranked for a bit and then began to start on one and then more than one cylinder. It took at least 30 seconds, maybe more, before I felt that I was positive that it would run on its own. Only then did I release the key. And, surprised as all hell, there it was at a perfect idle.

When the glow system is not running perfectly, it appears that too much fuel will serve to reduce the cylinder temperature and it will not start.

I had a similar experience with the 617 in the SD. I had a weak battery, a bad glow plug and 15 degrees ambient. No start. Not enough crank time. I took the unsafe method of a touch of ether. No start. Why? Cylinders too rich to fire, even on ether. Too much fuel saturating cylinder.

Remember, all the time that the engine is cranking, it is stuffing fuel into the cylinder that the cylinder does not need. If you crank it for 30 seconds at 1/2 pedal, it becomes less likely that you are going to ever get it to start that morning because of all the fuel in there.

My general feeling is that if it won't start with 1/4 pedal, adding more fuel will will probably be counter-productive.