Hello all,

I have an '86 F250/460/4 speed/4x4/flatbed. I recently had to replace the fuel tank selector valve on the frame rail. The new switch assy works just fine. The problem I'm having now is that when driving the truck, after a few miles down the road (between 3-5) the truck starts acting like it's running out of gas. It's mostly when pulling a hill or mashing on it. The enging doesn't have an EGR valve, nor does it have a catallidic converter. All of the fuel filters have been replaced, as well as the lines. I'm stumped. Any ideas??

I was crawling around under the truck yesteday and found a connector plug that is connected to the harness that runs to the fuel tank switch valve solenoid on the frame rail. The plug only has 2 wires, one is looped back into the plug itslef, the other wasn't plugged into anything (just kinda hanging out) but the plug did have a hole where a wire appeared to have been pulled out. Could this plug be the source of my woes?? I unplugged the connecter (removed) and the ignition switch wouldn't engage the starter. Is it possible that there is something else the plug controls and the missing/unplugged wire is the reason?

If anyone knows...PLEASE let me know. This one is kicking me in the ****!!



Thanks.......George

 

You might check to make sure all lines are properly connected to the new unit and that it is plumbed the same way as the old one. Your power problem sounds like a venting problem, as if you aren't venting the tank

The part about disconnecting the plug not allowing your starter to engage is beyond me. I'm sure someone has a Haynes or Chilton book with a wiring diagram. Your local electrical repair shop may have a copy they would let you look at.

I had an '85 3/4 ton and my Dad has an '81, both had dual tanks. The selector valve was an expensive rascal on both trucks. We decided to get a 3/8" t-fitting and bypass the selector. Just connected both tanks together at the selector and the t goes to the fuel line to the pump. The gauge still works and I'm not aware of anything negative other than one of the lines coming off and draining both tanks.

Hope this helps you.

 

Thanks for the info. I was thinking that it could be a venting problem as well. I have a Hayes manual that shows the layout of all of the lines going to and from the tank, and I did check the vent lines. They are ran the way the manual shows them be. I'm still stumped. By any chance could the new selector valve be somehow restricting the fuel flow when the fuel demand is high? It only seems to bog/starve for fuel during that sort of operation. I can let it idle all day long and it's fine. It seems to happen only after I drive down the road a few miles.
I read where you said that you bypassed the valve with a 3/8" T. I'm guess that with internal fuel pumps this will still work. Did your truck have internal fuel pumps? I'd be interested in bypassing my tank selector valve just to see if it could be restricting the flow somehow.

 

bad fuel pump perhaps?

 

Sorta sounds like a possible line restriction if it only does it when the fuel demand increases. Could be a bad fuel pump I guess. You said you changed the fuel filters. Did you do that before or after you changed the valve? Could have shook some sediment loose from somewhere in the process.

 

I didn't change the filters until after I had changed the valve.
i was thinking it was possible that it could be the fuel pumps...but how could both pumps go bad at the same time? It doesn't matter which tank I'm on, and when it happens, I can switch to the other tank and it's still the same thing.

 

Gtuck,
The trucks we have/had were mechanical pumps on the engine block. You may want to follow-up with the othe posts that concern fuel pumps; I hadn't considered that.

Are you sure you have electrical pumps in the fuel tanks?

 

Yep, Positive about that one. The night that the my tank selector valve bit the big one on me..(Why is it always at night and raining when that crap happens?) anyways...I was going to bypass the tank switch sel. valve unit and run directly from the tank to the fuel pump. But to my surprise...where the mechanical fuel should have been there is a blank off plate. And as my luck would have it...that 200 dollar switch valve on my frame rail supplies power to the pumps in the tanks. Can you say...It's a long walk to the main highway on this cold rainy night? But...yeah...it's they're electric puimps. Thinking about going mechanical though.

 

Dude...I had the exact same problem. Change the o2 sensor.

 

A while back I was having this problem with my truck acting as if it were running put or gas. I tried everything...filters, lines, regulators, etc...
It would run just fine for a few miles then it would simply bog down as if it were starving for fuel. After everything I tried, an older fella down the road came up and took a look and in a matter of about 5 minutes, he tells me to replace the coil. So I did. Why now? I already replaced everything else. So...30 bucks later, my F250 was running like a champ again and hasn't acted up since. Go figure.