1988 Ranger Dual Tanks Problems...

[RangerMan64]

Hello,

I have a 1988 Ranger with dual tanks. I don't think the front tank has ever worked, at least since I've owned it.

Here's the problem, when I flip the selector switch over, nothing seems to happen. The fuel level will stay the same, and it seems to continue drawing fuel from the rear tank.

What should I start testing to see what's bad?

Thanks

 

[wrecking-crew]

normally a bad pump is the problem but i think it may be a bad switch

 

[AllanD]

I'd look into the selector valve

This may require a helper to cycle the ignition switch
because you don't want the engine running while you are diagnosing,
but the entire switch circuit is dead unless the fuel pump relay is on
and running.... and with the engine off it'll only run for 10-12seconds.

As a guess I'd say it's either the offending tank unit or the control valve

The selector valve is one of those things labeled in the service manual as "not serviceable replace as a unit" I of course regard that as a challenge
and I've had decent success getting them apart (moto-tool Vs the flared ends of the rivets then stainless steel #6 screws and elastic stop nuts to hold it together.

If the motor inside....
Yeah, there is a small electric motor that powers a leade-screw...
which moves a crossbar, the crossbar both carries electrical contacts
to switch the guages AND power (I was mistaken in previous posts)
and the T-bar itself moves a pair of double acting valves to either side
of their neutral position

Now the electric motor can fail or any of the four O-rings in each valve assembly
can leak
This can be particularly nasty if the valve stem O-ring fails
because feed fuel from the intank pump will fill the motor chamber
and blow fuel overboard.

Particularly if you have done what I have... I've eliminated the frame
mounted pump and I run the output of high pressure pumps through
that valve, so when I popped a shaft seal O-ring fuel sprayed out
like from a lawn sprinkler... kinda spectacular even considering it
didn't find an ignition source....

I blew 20gallons of fuel overboard in about 45miles

It kinda interrupted my day....

If you weren't ~2700miles away I'd tell you to drop by on the weekend
and I'd take a look at it....

AD

 

[AllanD]

BTW, when the selector valve runs it makes a high pitched electric motor
sound as the little lead screw is run from one extreem end of it's travel
to the other.

there is no "center" position because the center obstructs both pressure
and return sides (seperate internal valve assemblies)

The fact that one tank operates normally indicates that the motor probably isn't working so the valve is in one position

Flipping the switch while someone is under the truck listening to it will confirm this.

If it was a mechanical problem with the valves you'd either have an
overboard leak OR a "Crossfeed" issue.

AD

 

[RangerMan64]

So you're saying the valve is stuck, and that is why nothing happens when I flip the switch?