Just bought an 87 F250 7.5L truck and it starts easily, idles smoothly, and drives nicely... until you reach 50-55 mph. When it reaches that speed, it dies.
It has dual tanks. When the selector is in the front position there is an electrical buzzing sound. When it switches to the rear tank it goes away.

I recently tried driving the truck on the freeway with the front pump on. As usual when I hit 50 it fluttered and sputtered and died. I shifted to neutral for a few seconds and with some pumping of the pedal, got it started again. Drove again up to 50 and it died. Repeat until home. When I switched it to the rear tank it didn't make a difference.

Other symptom is that the amp meter in my instrument panel goes between the last red line and above the first over charge red line. I am not sure what is causing this.

I need it to drive to Alaska in 5 days. 2300 miles. Don't want to drive that at 45 so THANK YOU for any assistance!

What I have done:
Autozone tested the battery and said it was fine.
Change the oil and used an engine grime cleaner.
Prayed a lot.
Cried a little.

 

Check fuel pressure.

 

Cat stopped up. Welcome to the forum.

 

Good luck on the trip.

As for the problem i would think teh cat would be a good start, But you have more than one problem going on here.

 

Good advice from everyone. I think I would start by checking the fuel filter which, I think, is in the carb fuel inlet. I would next check the carb float level.

 

I will head out and check check check. I think I shall take pictures also. Perhaps that will be of greater assistance.

 

What is a cat? Besides the animal...

And thank you for the welcome!

 

Catalytic converter. = cat.

 

there are 2 fuel filters if my memorey serves me correct. isnt there one on the frame rail too?

 

In this picture you can see that the brown spring to the left of the blue thing isn't where it should be. I fixed that. Not sure what it is for...
https://picasaweb.google.com/lh/phot...eat=directlink
In this picture you can see that the bottom is wet. It is wet with gasoline. What does that mean.
https://picasaweb.google.com/lh/phot...eat=directlink
Here is the whole thing. What part is the fuel filter? I have yet to get a repair manual for this truck and am relying on what I know about vehicles already.
http://picasaweb.google.com/lh/photo...eat=directlink

 

The The F/F is the little puppy on the right w/ NAPA printed upside down on it.

 

I have that removed and am off to get a new one. It looks pretty good but they are cheap so might as well.

 

Any thoughts to the amp meter in the truck not working correctly?

 

Or worse..."Is working correctly". DC volt meter readings off the POS terminal of your alternator to ground, will tell you what's really going on at idle & increased RPM's.

 

Could be the gauge, could be the charging system. If you have a volt meter measure voltage across the battery with the engine off, 12.5V and then again with the engine running, 13+ Volts to 14 volts +.