I have a 1987 f250 supercab longbed with a carburated 460 (Edlebrock 1406) and a t-18 4 speed. Here is todays problem.. lol. I got the truck running good,no popping, flooding, backfireing, etc. The truck has always started fine. It can sit for 10 minutes or 2 weeks and just bump the starter and it fires right up, you dont have to pump the accelerator or anything. Well lately, I go to start my truck to go to school, and I have to crank it forever. I can pump it when cranking, pump it 2 or 4 times then crank it, floor it or hold it at half throttle when cranking it, and theres just no fire. Its really annoying, and I have looked in the carb and it squirts fuel when I pump it, but doesnt smoke once it starts which makes me believe its not flooding but it is getting fuel. Choke is not stuck or anything. I have to crank it with my foot off the gas and it will barley catch, die, try again, it barley catches and if I give it any gas it dies. After it catches pretty good it will stay running or rev up and do whatever you want and is fine all day. It has been doing this for 5 days now, didnt ever do it before, weather is not any differant it gets to about 45 to 50 degrees at night which is usual. Sorry to be so wordy and it is really not a big deal but very annoying to me lol.. so what do you thing it could be? Something in the carb, something electricly.. coil or condenser? thank you

 

Try the 80-86 forum. You're on the boarderline for your truck. This forum typically deals with efi, which the 460 didn't get til 88. Sorry.
I would say, double check the choke. Make sure it's closed.
Double check spark. The duraspark box does go bad occasionally. If your coil is old, replace it.
Give it a good tuneup, double check carb settings, let us know how it goes.