1995 F700 429 V-8. Truck starts, idles and runs well at all speeds, but when running at full throttle up a long steep grade, the engine will lose power fairly suddenly almost as if it is running out of gas. After the speed drops down to around 20 mph the engine seems to gain power again and it will accelerate reasonably well. Would this likely be a fuel or ignition problem? Assuming the fuel filter may be clogged and need replaced, where is it located? Thanks, Tom

 

Dual tanks? If so, try switching tanks while on the grade. I had the same problem and when switching tanks felt like a turbo would kick in.....was the fuel pump in one of the tanks. The fuel filter should be in front of the tank, mounted on the outside frame rail, at least that's where mine is on a '91. You'll need the special fuel line tool to get it off.

 

Big single tank with plenty of fuel in it.

 

Sounds like fuel - put a fuel pressure gauge on the fuel rail (with a long enough hose so you can watch it while driving) and watch the pressure as you climb that hill.

The fuel pump might not be able to keep up anymore.

 

From OP: I think the problem may have been due to the truck sitting for long periods with old gas. I changed the fuel filter and added some fuel injector cleaner to the gas and the problem went away almost immediately. I've since put almost 3000 miles on the truck with no problems

 

bumped for buddy