When running on front tank return fuel was going into rear tank, so I replaced intank pump. No difference. I note now when running on rear tank return fuel going into front tank????? I get 2 different responses to "is there a selector valve in my 95 F-150 fuel system" and if so where is it? Is it possible that the return lines are simply crossed?

 

The majority of the time the tank that overfills has a defective shuttle valve and that pump assy needs to be replaced. I believe you replaced the wrong fuel pump assy .

Now I don't know why when running on the rear tank you are having the same problem , did you drop the tank and clean out any garbage that could have messed up the new pump in the front tank ? Sounds like that shuttle valve is not working correctly either.
If you did not change the entire fuel pump module assy the problem is still there.

 

I guess I should have explained my problem better. I first noticed the rear tank growing gas when running off the front tank, so I replaced the fuel delivery module in the rear tank. Problem still there, and now I notice the front tank growing gas when I run off the rear tank. I have been told the 95 model f-150 does not have a selector valve. If it has a selector valve where is it located? I did not see it when the rear tank was down.

 

Bro, visit some good mechanic he can surely take out the problem from the root.

 

I believe those fuel pumps are the hi press type and don't require any booster pump.
That said, Within the fuel pump module should be a shuttle valve that for example,when the front tank is pumping the shuttle valve in the rear tank module is supposed to prevent returning fuel from going into the rear tank, and the opposite when the rear tank is pumping.

 

Thanx for the replies. I've had the truck to a mechanic who says the truck has a selector valve, but does not know where it is, and his contact at a local Ford dealer has been unable to tell him where to look. I don't think the problem is the check valve, since if it is it would mean that both original modules and the replacement (rear) module have defective shuttle (check) valves.

 

I'm wincing about now !
Where did you purchase the replacement modules?

 

Local parts store, not cheap but rather a quality part. Replacement module 9only replaced the rear module) had no effect on problem. Thinking there is a switching valve which may be the culprit--or maybe return lines are switched???

 

Do you still have the module you removed from the rear tank, if so consider checking the outlets and see if you can determine which is fuel out, fuel return , vapor , and if any type check valve tube .
Questioning the possible switching of any lines, how long have you owned the vehicle, has it ever worked properly before, these are questions that if answered might lead to a possible cause.
I always ask where the parts were purchased because so many times new parts are defective right out of the box and if you are not positive of how a system works the assumption of a new part is good can get us into chasing a wild goose looking for a problem that isn't there. Those of us that have been burned a few times will prefer to buy from the dealer when possible.

 

I have had truck for a few months and always smelled fuel when exiting after driving. I used to keep both tanks full and would switch at1/4 tank to keep fuel fresh. I do not have old module. I think this problem has been present since I've owned it. I shy away from 3 modules being bad as the odds are just too great. I do appreciate your thoughts.