I have a 96 F-150 with a 4.9L Inline, 2WD, Manual. My rear tank has never worked since i bought it, however i filled it up the first day i got it. Well recently it would run on the rear tank, but seem to run a little crappier. So i ran it down to about half a tank in the rear tank. Then i filled up my front tank, with a full tank. Well it wasent 3 days later i had half a tank in my front, which should have not even been close as much as i had been driving, i switched over my rear tank and it was full. So i talked to a couple friends and they said it was probably the check valve. What i was wondering is how hard is a check valve to replace, has anyone done it before and how much it would cost for the part?

Thanks.

 

You need to replace the rear fuel pump, the check valve is in it.

 

The Check Valve is located in the rear tank? Also i checked on the price of a new check valve $90. How hard is it to replace?

 

Thats a dam good price Be sure your getting a fuel pump as the checkvalve is not replaceable. To replace it, there are two methods. One is to lift the bed and replace it from above, the other is to drop the tank and replace it on the ground. You'll need a new lock ring and a brass punch to help remove the old ring. Simply disconnect the wiring and hoses, remove the ring, pull out pump, put in new pump, install new ring, reattach everything. Its sounds easy but can be a PAIN when working on these old rusty vehichles, the main thing is to avoid sparks,, cigarettes, lighters....

You should check the condition of your tank mounting straps, replace them if they are rusty.

 

and also replace the tank if it is rusty.

 

SubFord would be the expert on this post, is there a check valve in both tanks, or just the rear. If there is one in both, then why would the rear tank be filling up when the front tank is selected? Also, is the check valve in the fuel pump, or is it a seperate thing all together?

 

Oops I accidentally posted twice.

 

When I run off the back tank, it fills the front tank, unless the front tank is already full. One hot day with 2 full tanks at idle it did not run right off the back tank, like it was flooding or starving, don't know...but gas was coming out the vent on the front tank.

 

This was covered in detail on another post but briefly if you run on one tank and the other fills up the one filling up has the bad check valve. There is a reservoir in each pump and that is where the fuel is returned to, not the tank (but the fuel pump is in the tank). The fuel return line goes to both fuel pumps and the pump with the bad check valve let the fuel back into the tank.

The check valve is in the bottom of the pump and yes both tanks have check valves.

Note that we are only talking about 1990 and newer trucks.

 

I have 94 and when I run on the rear tank it fill's the front tank up also,so does that mean the front tank has the bad check valve?

 

Yes that would be the indication.

 

thank's subford

 

For more information in detail on this subject please read the following links.

'93 F250 dual tank crossflow problem:
https://www.ford-trucks.com/forums/showthread.php?t=455062

dual tanks/fuel pump questions:
https://www.ford-trucks.com/forums/showthread.php?t=456070