82 f100 4.9l straight 6 has been leaving me stuck at the gas station and the grocery store lately. I've ran a compression test and everything in the engine seems good. The choke seems to work fine. The problem is.. some days I will drive it to a gas station or run some quick errands after work and when I go to start it back up it won't start. It turns over, but doesn't fire up. The trick I have resorted to is turning the key and pumping the gas to set the choke. It will eventually start trying to get going faster in correlation with me pumping the gas, and just as it seems to have any potential in starting. I flip the key back and turn it on again (while still pumping) and it will slowly start up. This trick hasn't failed me yet. But it takes too much time, and I know it has to be doing some damage. This only happens after short trips. Not even during first start up on cold mornings.

Anyone have any clue to why this is?

 

I have had similar problems and found it to be the ignition switch that is mounted on the top of the steering column just behind the dash. It is common for the little prongs on the switch that hold it together to loosen up and while the switch is in the crank mode it does not allow current to flow to the coil. When you start it don't hold the key in the start position all the time and back off it a little and see if it starts. Mine was worst when it was cold.

 

The next time it happens, try just holding the pedal to the floor rather than pumping it.

Whatever problem you are having is from the heatsoak when it sits. It could be the fuel boiling over into the intake, it could also be the coil or ignition module providing a weaker spark when hot. Or both.

 

Search this forum for "hard start". my 1980 has the condition which sounds as if i need to set the ignition timing.

 

If the engine isn't fully warmed up, I'd bet it's a choke issue. My 80 300 will do this as well.
It always happens under this type of situation: short drive with cold engine, shut off for a couple minutes (like running into a gas station) then restarting. I have found that this situation calls for extreme care when re-entering the truck, to avoid touching the throttle pedal, otherwise the choke sets fully, and it will not start. When I do accidentally bump the throttle pedal, it requires lifting the air cleaner and holding the choke flap open while cranking.
I've done this a couple different ways. If I'm not alone, I have someone else crank it over. Alone, I either turn on the key and hold the flap open while bumping it over at solenoid or stick a screwdriver in the top of the carb and crank it with the key.