ok i am having a problem getting my 1979 f150/bronco 351m to start...
here is what happened.. i swapped my bronco body with a f150 body everything fit but for rear mounts on cab..but i got everything hooked up right and the gas sat for about 2 months and so did the engine during the snowing times here in missouri but i had the engine covered and everything so nothing got into the carb....i tried to crank it over and over again and no start ..so i emptied the gas and put new in and after a little bit of crankin it started.. and ran it for a good hour to 2 hours straight..wasted a ton of gas but it ran great and idled perfect..so i parked it for about 2 days and the next time i tried it cranked but no fire...but when i pumped it it tried to fire but didnt..so if i floored it. it would act like the timing was off but nothing has been touched since the last start so that couldnt be the extact problem...and so i changed the gas again..no luck..and then i changed the inline fuel filter (the one next to the carburator)..and still no luck...but now when i try to crank it and floor it it starts and then dies..but when it dies it makes like a really loud vaccum suckcon sound....i have ran out of ideas that are easy to do....any one got any ideas..i am stuck at this point..Thanks in advance..

 

Possibly a bad Ignition Module. When these start to go, sometimes it'll start right up, next time it won't. Look on the module (left front fender apron) where the wires feed to the module...there will be a colored plastic square, prolly either RED or BLUE. If it's the RED one, that has been a dog of a module since 1977, and are very prone to failure.

 

First you need to determine if you have spark, fuel, or timing problems. Check the timing according to the repair manual. If it is way out you may have a bad timing chain. Check fuel pressure and delivery according to the manual. Check to see if you have a hot blue spark.

 

it was my timing it was 180 out...well it works now thanks everyone...