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My 1985 Ford F250 please read and help

I have a 1985 Ford F250 with a 351 windsor in it. I just pur a new fuel pump and fuel filter on my truck and it starts and drives but back fires really bad. Sparks are hitting just fine and im almost positive that all vacume lines are plugged in or plugged off. Any ideas on what it would be? What about the float could it cause that. Its fine at half throttle but backfires abynore than that.

Start at the tank and look and feel all of the lines. Don’t miss a inch. My 85 Bronco had a filter close to the tank thats not in any book. This filter was hid and hard to get to. It was factory too. Also you may have one in the tank. Mine did the same thing till I found this filter and replaced it.

When does the engine backfire? As in’ accelerating, decelerating, starting??? And is the truck carburated or injected?

Check the timing?

Both Cig and Rod asked the right qustions, assumeing its a carb’ed truck then your carb may be leaking… However it is more likley to be out of time if you are actually backfireing… have you checked ??

FWIW, the last few years that Ford used carburetors on their F250s and F350s there was a problem with the AIR/smog pump. On deceleration the engine gulped a few shots of rich mixture due to the high vacuum and if the smog pump failed to bypass as it should the explosion in the exhaust could blow the muffler off. And often, when the engine was shut off immediately after being accelerated an explosion occurred a few seconds after the key was turned off. It could be quite spectacular in some locations.

i looked at it yesterday and i put new plugs and wires in it and she still is but only when my is going. I get no power up hills but it will drive just really poorly. I dont have and more filters or pumps bronco thanks tho. Do you guys think it could be timing