Fuel Problem..PLEASE HELP!

[RangerMan64]

Hello,
I am currently having a problem with my front gas tank (I have dual tanks.) For a while, the fuel selector switch was busted and I could only use the rear tank. Today, I bought a new fuel selector switch and installed it. Put some gas in the front and started her up. Now here's my problem. I started it on the front tank and it said I had a little less than a forth of gas left. No problem. I switched it over to the rear, and it reads the same! It seems like it is acting like I have one tank. It acts like it's siphoning gas from the rear. Please help!

 

[AllanD]

The dash mounted switch controls which in-tank pump operates.

the selector valve actually controls which sender unit is connected
to the guage and FAR more importantly determines which tank the
return fuel goes to...

"Cross-feed" is the worst thing that can hapen in a dual tank system
and with the design of the six port selector valve, it's difficult
(but not impossible) for a crossfeed to occour.

All it takes for the valve to malfunction and "cross-feed",
is an aged O-ring.

If you can follow my description (I also discuss this in "Houston we have a problem" in the General discussion forum)
The selector valve is motor driven, the motor drives a miniature "lead screw"
which moves a mechanical "crosstree" back and forth.

On either end of this crosstree is a small "fork" these engage the valve stems.

The valves (there are two identical valves in the housing) are double acting meaning that without the crosstree either pulling or pushing on them they sit in a "neutral" position

Pushed in they connect to the rear tank, pulled "out" they
connect the front tank

Crossfeed does happen, but in a stock system like yours unless the tank vent (or the fuel return line) is obstructed it will usually not "blow fuel overboard"

that all presumes that the various O-rings and Circlips deep inside the valve
assemblies are actually where they belong.

I have one "failed" valve on my desk that I finally bothered to disassemble sufficiently
to diagnose. it's one of two I dismantled to make the "good" one that I'm running now.

The motor worked fine, the supply (pressure) side valve works perfectly.

the return valve OTOH has one teeney-weeney E-clip that rusted off the
stainless steel shaft and that allows the valve stem to float freely in one direction
so basically if the selector switch is set for the forward tank you'd never know
anything was wrong, if OTOH you set it to the rear tank the return side valve
allows fuel to flow freely to the front tank as well as the rear tank.

I might add... with sufficient force to cause the filler cap to vent.

My system is somewhat modified in that I'm runing high pressure pumps in each tank (and no frame mounted high pressure pump) so if I have an obstructed fuel line or clogged vent, or even a clogged fuel filter something might give out.

My biggest worry was literally blowing the selector valve apart, but in actuality
the "worst" that can happen is it can blow the pressure side valve body forward
in the housing past the spring steel retainer that holds it in place.

NOTE: you will never see most of these parts I mention unless you drill out
the rivets and actually disassemble a selector valve.

I just this week discovered that the '85-87 Rangers with dual tanks uses
the same valve as F-series trucks up to 1988.

and on the F-series trucks the valve isn't "protected" (read: made inaccessable)
by a metal shield like it is on Rangers.

AD