Ok, I thought I might have a slipping auto tranny, BUT today I'm thinking this might be the fuel pump?

Here are the symptoms....

While on the highway and the truck is at speed and kicks to OD the truck starts to loose speed and I feel hesitation. If I try to accelerate the truck will down shift, RPMs will climb but I still feel hesitation and the truck will barely pick up speed. The hesitation doesn't seem as bad at higher RPMs though. Finally when I get back up to speed I back off the gas and the truck goes back into overdrive and will either hold the speed or do the same thing again. It seems to keep getting worse. Some days it doesn't do anything at all, toady was really bad. I also floored it after making a turn and the truck just bogged real bad and wouldn't come out of it until I backed off the gas.

In a previous post I mentioned that after a stoplight at the base of a railway overpass I was having a lot of trouble accelerating. Truck was stumbling and I could hardly keep up with traffic!

I'm also getting 10mpg with 95% of my daily commute on the highway.

NOTE!!!! Today I thought with how bad the truck was running on the highway home that for fun I'll put the truck to run on the back tank. Well, at this time I was on the gravel and with the rough road I wouldn't feel any hesitation if there was any BUT I floored it again and the truck seemed much stronger!!!!

What's going on?????

 

What vehicle, engine, trans are you having this problem on? (your name implies an 86 but your profile shows a 95 f250) Is/did the CEL come on?

It sounds like a vacuum leak but lets pull any codes first.
You can visit www.fordfuelinjection.com and do it yourself, all you need is a jumper wire or paper clip, pencil and paper; or visit one of the autoparts stores like Autozone and see if they will pull them for free. If you go to the autoparts store grab a Haynes or Chiltons service manual, they are cheap and come in real handy.

 

Possible a seal issue around the fuel pump lockring on the front tank? Per Popa Tim, have you checked for codes, check engine light blinking? From the post, I'm getting that your truck runs just fine on the rear tank, is that correct? Please list year, type, engine, transmission, if you could, or just put it in your signature and you won't have to list each time you post. Thanks.

 

Sorry guys, yes it's my new 95 F250 5.8L, E4OD, 4x4. I'll change my sig.

No my CE light is not on, don't see any obvious vac leaks. I'll pull codes tomorrow.
On my way home today has been the worst acting up for the above symptoms. 3/4s the way home I floored it while on the front tank and the truck just bogged and didn't accelerate at all. I backed off and then it recovered and picked up speed. A mile down the road I stopped to turn and fipped over to the rear tank. I floored it again and this time the truck accelerated with gusto!

 

I'd say it's a front tank issue, clogged sock, maybe. Junk in tank. I'd replace the fuel pump if going to all the trouble to drop the tank and clean it out. As you examine the lockring when removing take a close look at the gasket for deterioration.

 

Ok, I'm going to run on the back tank for the next couple of days and see how the truck runs. I'm also going to keep track of the mileage to see if it's better than the front I'm always running on.

 

Remember that the excess fuel, overpressure etc vents back into the front tank. You won't have a true picture of mileage until you use both tanks.

 

yeah, I know about the fuel going back into the front tank. I'm just going to see if my mileage increases while using the rear tank with the good pump since driving around only on the front was giving me ~10mpg! And this is 90% highway driving in and out of the city.

NOTE: Yesterday I was driving down the highway and filpped on the front tank, felt a bit of hesitation when it flipped over. I then floored it and the truck did not pick up speed. Flat on it's face. A minute after I flipped to the back tank and floored it and the truck buckled down and accelerated strong.

So could I have crap in the tank or is this a bad pump? I did recently runt the front tank bone dry....

 

I think you've pretty well defined the situation. I think your front tank pump is going bad or has gone bad. I did the change out in right at 4 hours with the addition of changing the fuel filter on the frame rail. It's not too difficult. It matters if you have a metal or plastic tank. The plastic tank fuel pump was around $134.00 and the one for the steel tank that I had to buy was $173.00. At least I didn't shell out more to have it replaced. There's some satisfaction in that ya know.

 

yup, definately the front pump is shot. I'm going to pull the bed and change the pump that way. Gives me an excuse to go over the wiring/ frame/etc. to make sure everything is good too!

 

Make sure to disconnect both filler necks and all wiring so as not to have any surprises. Shouldn't take you too long though.