hey guys just like the title says my 75 f-250 has been bogging down it all started when my truck was sitting for about 1 week after not being started, but prior to this week it had been running great but now i get dark yellow fuel in the fuel filter then i would get it started with a little bit of starting fluid it would idle fine and eventually the fuel filter would clear up, if i hit the gas a little bit it sounds like it will run good but then i get to about 1/10 throttle and i hear a little whining in the engine and it just sounds like it doesnt want to go to any higher RPM's it also sounds like its not getting enough gas but i havent even touched the truck since then so any words would help me out here.
Its a 390 no special stuff on it just a stock 390.

 

Anyone tamper with the fuel tank?

I'd take a fuel sample for a visual and smell.. Any chance someone put diesel in it? You could run a temp fuel hose off of the F/pump and into a small fuel safe container. If it runs good, there's the answer...

 

Hey thanks I will be sure to check that out but we live in the country and not to many people even drive by but I guess there's always someone that will do that and do you think that diesel would clear up in the fuel filter it seems like it wouldn't clear up after a couple mins of idling. Thanks

 

Just throw'n out idea's..

I've seen more than a few polluted gas cans dumped into a clean tank causing issues, diesel (sometimes the significant other or friends) pumped in at the station by mistake, white gas, just about everything. Rust, water, resin stank gas, especailly on the 'safety' cans with the lever cap and screen that you can see the bottom. Diesel tends to be 'amber' looking in higher volume, not so much if a small sample..

The whining,, not sure what your hearing. But any 'color' to the fuel seems suspect to a bad tank of gas, or another type of fuel, or tampering. The fill hoses at the fill to tank like to split/rot and can be a place of intrustion for water ect. too.

A polluted fuel system will cause poor top end and overall performance. Sometimes not so much at idle.. Although if diesel contaminated, (in a higher concentration) will be hard to start and usually some extended cranking, more so cold..

 

well we had the tank cooked out about 1month ago so its not to tank and i just put 10 gallons of good gas into it and i replaced the hoses that come out of the tank they were in terrible shape so i thought thats where the air was getting into and it was losing suction but that didnt change anything when i replaced the hoses i just replaced the fuel pump, new carb, new fuel filter i just dont get it

 

Now that you have cleaned everything and even replaced the carb I would change the plugs..If they are sooty black ..I have seen this when someone accidently put diesel in a gas engine..or perhaps kerosene .
I had a ford f250 for my shop truck..parked it and the next norrning it was hard to start and would not accelerate..turned out to be my timeing chain .

Set the crank pully on TDC take off the distributer cap and mark the rotor position
turn the crank by hand counter clockwise till the rotor starts to move..mark the crank..now turn it clockwise till the roror moves ..mark that..
the rotor should move with almost no space between the marks.. 1/4 inch is ok 1/2 inch and you have a bad timeing chain

I have worked as h heavy equipment mech for about 45 years..hope this helps ..let us know

 

i ran a temp fuel line into a 5 gallon gas tank of new gas fuel filter cleared up but still ran bad. but now i can feel and hear a leak on the base of the carb but its not the carb thats leaking so iam pretty sure thats where my "Whining" is coming from. so its not the gas, so that leads me to believe that its the carb. and the rotor olny moved 1/4inch so dont really want to buy a new carb if i dont have to.

 

When you replaced the carb did you match and replace the spacer plate gaskets? EGR passage area/ brake booster flange.. Odd, that with all the new pieces, and the tank flushed it would still flow any color in the fuel. Also, that with a vacuum bleed under the carb that it idles fine as noted, or that it was fine and stable a week prior.. Good place to start though, getting the 'weez'n corked up But even with a base vacuum leak, should'nt kill the top end performance.. Any improvement if the EGR is unplugged?

So,, all the new pieces were added, (why) and ran fine,, now poor performance. Run the same as before the new parts? Still a Motorcraft carb.? What brand reman. unit?

 

I would almost think there was junk in the carb blocking the main jets..what do the plugs look like

 

Just a thought. Do you have an in-line filter, in-carb canister/ filter or both? I've worked on drivability issues with vehicdles that somebody put an in-line filter on and forgot or didn't realize that their carb had a canister or Sintered Brass filter in it. It was normally the carb filter that was plugged causing the issue.