I've never cranked a truck, but several of my old tractors are crank start.
As mentioned, Do NOT wrap your thumb around the crank!.
Also, do not try and "spin" the engine. Only go half to 3/4 a turn at a time, pulling up on the crank. I usually engage the crank at about the 3 or 4 o'clock position and spin it around to 12. Then repeat as necessary.


Rich
1947 Loadmaster
1947 Chev. Loadmaster
1959 Chev. Viking 40

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