bpardo19

I have a 1993 f150 2wd 300 straight six with the dual tanks....I replaced the intank fuel pumps about 2 months ago...the rear got a motorcraft and the front got a spectra..... They both work great and both have a fuel pressur of about 50-60..... For some reason i will fill both tanks up, I use the front tank first till it is low on fuel, then switch to the rear. Once the rear is almost empty, Ill switch back to the front and there will be about a quarter tank in there!!!!!!!!! What is going on and how do I fix the problem......

Also would the fuel vapor canister have anything at all to do with this????????? Also what is the purpose of the canister....

Thank you so much!

bpardo19

Anyone got anything on this issue?

GhostriderI

I read another thread (will try to find it again) talking about dual tanks that would transfer fuel from rear to front tank and they talked about the selector valve not working correctly.



https://www.f150forum.com/f13/fuel-s...nction-133536/

Hope this helps

GhostriderI

Fuel vapor canister collect the fuel fumes (vapors) from the fuel tank vent when you start the truck the fumes are removed with the vacuum system and burned in the engine

bpardo19

But do I have a selector valve on a 1993 f150???? I thought they stopped the valves in 92???

GhostriderI

There has to be a way to choose the tank to pull fuel from if you have two tanks. Power to the correct pump and sending unit with two one-way check valves or selector valve (which acts as a the one-way check valve).

bpardo19

Yes, i have a front and rear selector switch on the dash. I dont see how a check valve can malfunction on a new pump

GhostriderI

LMC list it as a Fuel Reservoir Assembly bottom left.

http://www.lmctruck.com/icatalog/fd/full.aspx?Page=55

GhostriderI

The check valve keeps one tank from pumping into the other. You select the rear tank that pump and sending unit is powered, as the line builds pressure fuel will follow the path of least resistance, no blockage in the line fuel flows to the other tank, a valve is directional flow control fuel in from port a can only exit port b switch tanks fuel in port d exit port b only no cross flow between tanks.

GhostriderI

Does this truck have injectors? I have and older one with a carb.