I have a 1985 f150 with a carbed 300 i6. 4 speed. She has duel tanks but I only use the rear tank as the previous owner told me it wasn’t working and I’ve never started to trouble shoot. She was my daily until she quit running on me. I can get her to start and turn over but then she quickly dies. The truck will run with fuel in the carb. I have replaced my fuel pump mounted on the engine block, cleaned my carb, replaced my fuel filters, replaced my old rusty tank in the process and cleaned up the old sending unit, which appears to not have a pump on it. Any thoughts to get her running again? Another thing, when she runs the 3 port tank selector switch gets super hot. Haven’t replaced it or taken it out of line yet but seems like it could be an issue.

 

Are you talking about the valve inside the left frame rail? The 3 port valve is spring-loaded to feed from the rear tank on later models, or the front tank on earlier models. When the non-default tank is selected, an electromagnet inside this valve is energized and the innards move to connect that tank to the engine. It's normal for the valve to get warm when the electromagnet is energized. Super hot? That doesn't sound right, however.

For now, since you are only using the rear tank, you can easily bypass the valve. Disconnect and stow the plug. Use a short length of fuel hose to connect the desired tank to the common feed to the engine. Plug the line from the inactive tank. You should be fine to drive like that until you can take care of the valve and hopefully have both tanks back in working order.

With any luck, the valve was restricting fuel flow and causing your problem. A dollar's worth of fuel hose and little bit of your time should tell.

 

Yes that is what I was talking about! My head was going in that direction so I’m glad you were thinking that too. I’m gonna work on that and see where it goes. Thanks!

 

I would also bypass the valve like Karl said this way you know there is nothing between the good tank and fuel pump.

I will also say if you did not replace ALL rubber hose with new do so and make sure you use the right size.
I tried 3/8" from a gas can on the fender to pump and it would not pull fuel even with 2 clamps at the pump!
I went with 5/16" hose and it worked. I also used 5/16" to replace ALL rubber hose and been working for over 5 years now.

As for the 3 port valve you can get it on Ebay for under $40 https://www.ebay.com/sch/i.html?_nkw...023.m570.l1311
Oh remember once the valve is bypassed the dash switch will still show the level in either tank so it you switch to the front and it happens to read full because you are running on the rear you will run out of gas.
As Karl said the valve defaults to the rear tank so I run on the font first then switch to the rear. I did some work under the truck and after a few days did not see the front level drop?
I switched to the rear and seen it was no longer full. The valve wire shorted out blowing the fuse and with no power to the valve I was running off the rear but reading the level in the front.
Dave ----

edit: Welcome to FTE

 

Beware: The 1985 and 1986 ford 300 six use a different style fuel selector valve then earlier years. Below is a link to a post with photos of both types. Read the post for more info.

https://www.ford-trucks.com/forums/1...ml#post9757470

This type of fuel selector and the associated parts have not been available for a long time. The connections are pushed ON and are sealed with an o-ring. It is held in place with horseshoe clips as shown in the photos. These clips are very easy to break and are not available anymore.

Given the above I would focus on trying to get the fuel selector to release.
It is spring loaded to operate on the rear tank. I would disconnect the power wire at the fuel selector valve. And then I would tap on it lightly with a hammer hoping the spring pressure will move the valve to the correct location.

The fuel selector valve is located on the driver side frame rail on the inside, near the front of the bed. It is bolted on with two bolts.

If you were unable to get the valve to move to the correct location with internal spring pressure, you will have to follow the advice above and bypass it. This will be a complicated thing due to the plastic lines and existing connections.

I wish I had better news, good luck.
Jim

 

sounds great Dave! I appreciate the insight. I haven’t replaced all the line, I just flushed it out. But I’ll definitely look into doing that too.

 

Jim, That is the first I have heard that the 85/86 trucks used a different valve.
But after reading the link you posted I would get the early valve and replace the plastic lines with steel or Alum.
Just use short rubber hose to go between the metal line and the senders & valve.

I am not saying this is the right way to do this (and I would not) but I seen posted where hose was used on the plastic line just dont tighten the clamps too tight as it can crush the plastic tube.

FYI any valve you get will have a different hook up than what the trucks wiring has but just cut the wire and put the right end on.
Dave ----

 

I had a thought that I thought I'd throw out there...

If your dual tank fuel system doesn't have in tank fuel pumps and you use a three port valve I think it might be possible to tee the two tanks together. I think the rear tank has a higher bottom elevation so having a working rear sender would be good. You would draw from both tanks simultaneously and you'd suck air when one tank went dry. The tops of the tanks are pretty equal in elevation. Just a thought here, what do others think?

 

The 3 port valve is cheap enough and easy to replace I would just replace it if I was running 2 tanks.
Now I understand his front tank is questionable at this time and being he cant get fuel to the pump I would bypass the valve for now and when he has time / money to get the front tank & valve in working shape.
The only bad thing of having 2 tanks is the money it takes to fill them
My front is a 16 gallon and the rear 19 gallon like all rear tanks. I run the front down to about 5 gallons or a little lower and the rear to 5 gallons so it 25 to 28 gallons at fill up.
Dave ----

 

I missed that his front tank is questionable. Gotta fix that first. Then he probably can decide to tee or replace the three port.

 

I just dont see Teeing the tanks to a common supply to the pump working as you said it would pull from the tank that is easier to pull from.
Now it may pull some fuel from the other till the easier tank was empty and you are stuck on the side of the road.

Unlike a big truck where both saddle tanks are on the same plane to pull evenly from they also got 2 fuel gauges so you can see just what each tank has cant really do they in our trucks.
Dave ----

 

The tee would have to have equal length fuel lines both sides as a starting point. But this is just an idea for the time when a valve isn't available.

 

I cant see it being equal both sides when you have tanks at different distance from the supply.
If the truck is a short bed tank sizes are different so I can see the pressure on the supply tubes but could be wrong too?

Most of the time the 3 port valve goes bad it is stuck on the default tank and that is the rear most of the time, at least on mine.
We also tell most to just bypass the valve till they can replace it if it gives a problem.
Dave -----

 

To get equal draw on multiple lines they will have to be equal length, and overall height.

 

You have to plumb it equal length to each tank from the tee. So to make it with out slack one side or the other, the tee would be about in the middle between tanks. Then run to the fuel pump from there on a single line.