Fuel Tank selector issues

I have a 1987 dual tank ranger with the 2.9L V6. I purchased this truck a few months ago and I am unable to switch the tank over to the rear tank. what could be the cause of this issue? what are the common failed parts? how do i test the system/parts? I cannot find any info on it anywhere. it is a stock system to my knowledge.

The schematic for the dual tank system is on page 24-35-3 of the Ford manual.

The problem is most likely the selector valve itself.

while the switch on the dash switches which IN TANK pump gets power
It is the six port valve on the frame that controls the fuel feed, fuel return
and which level sender is connected to the guage.

The six port valve is a somewhat complicated.

There is a small electric morot inside which powers a small lead-screw.

that lead-screw runs a crossbar up and down it's length.
Electrocal contacts on the ends work a crude switch logic
(in conjunction with a pair of diodes) to reverse the motor
to run it from one position to the other

the contacts on the opposite end connects the sender units to the guage

That little crossbar shuttle also does something else that's very important.

It works the valves (there are TWO) and it is best to think of them
as a pair of double acting valves, not unlike single pole double throw
"switches"

the valves supply fuel through their "Center port" to the high pressure pump on the frame and depending on weather they are pushed in or pulled out determine which tank is open.

This valve POSITIVELY CONTROLS the flow of the return fuel to the same tank as is open to supply the engine via the HP-pump.

If the valve does not shift position NO FUEL will flow from the selected
tank even if the pump runs


The valve CAN be "fixed" if you have another (with a different problem)
to use as an organ donor.

However this will require removing the valve from the truck,
disassembling the valve (it is riveted together)
determining the EXACT problem with it and reassembling it.
(3/4" long 6-32 stainless steel machine screws preferably with
elastic stop nuts)

(If you have problems finding the right screws ask me I was
forced to buy 100each of the nuts and the screws the last
time I needed FOUR of each.)

Organ donors?
The '88 ranger (last year dual tanks were offered on the ranger)
uses the same valve however it uses a different electrical connector
from the '85-87 EFI duel tank rangers.

Late Carb and early EFI econolines and even some econoline diesels
use the same valve.

I got my last two valves out of econoline box vans.

With that as a background any other questions? (there should be!)

AD

what is it doing or not doeing, is it just not sending the return to the selecting tank?
thats a comon problem with dual tanked fords(my dads truck does it)
either way listen to the master and dont be afraid to ask questions
and the master is most certenly allen d

lil red said:

what is it doing or not doeing, is it just not sending the return to the selecting tank?
thats a comon problem with dual tanked fords(my dads truck does it)
either way listen to the master and dont be afraid to ask questions
and the master is most certenly allen d

Click to expand...

If your daddy's truck is an F-series it is NOTHING like the
dual-tank fuel system on a Ranger.

If he has a '90-or earlier his trucks fuel selector switch electrically controls which pump switches on, but the selector valve is a "passive" device.

the low pressure piump in the tank acts on one side or the other
of a double acting diaphram valve that trips one way or the other
to select where the return fuel goes.

Typically the diaphram ruptures and pressure fuel flows back into the NON powered pump into the tank and the valve cannot select which tank to command the return fuel, so eventually the resulting crossfeed fills the tank to the point where the filler cap looks more like a sprinkler head.

If he has a '91-up F-series the control system is MUCH different.

the 1991 up has NO "selector valve" at all.
The selector switch on the dash controls both the pump and guage selection.

Internal to the tank there is a special cannister that the pump is mounted inside. the fuel pressure is used INSIDE THIS RESERVOIR to open a spring loaded shuttle valve that allows return fuel to flow into that tank

the check valve on the high pressure pump theoretically inhibits back
feeding through the unpowered pump.

In practice either the gasket at the pump outlet (internal to the cannister) leaks or the internal check valve (inside the pump itself) does, so ford has a TSB part that SHOULD be added to any '1991-up dual tank F-series.
P/N 1L34-9J274-BA

this is a supplemental check valve that is installed EXTERNAL to the tank on the pressure outlet of the pump unit to prevent backfeeding into the unpowered tank.

I could be wrong, it COULDbe 1990 that ford switched to the in tank high pressure pumps.
the simple way to determine which system is on the truck is to look for a frame mounted PUMP or the frame mounted diaphran control valve. if it has EITHER the problem is in the diaphram valve.

the later trucks liteerally have nothing more in the fuel lines than a "T" brazed into with the stainless steel fuel lines.

AD

AD

I just bookmarked this thread!

well whats happening is when I flip the switch nothing happens. The fuel is coming from the front tank. The sending unit isn't working right in the front tank. I get no response from the rear tank. its like that switching valve is stuck or frozen for the front tank.

well, as I already told you

the switch on the dash actually switches the power to the fuel pumps in the tank.

the selector valve only switches the fuel guage sender units.
though it silmutaneously works the two valves

So when you flip the switch if the selector valve doesn't move
the engine should die, because the low pressure pump in the tank
should be trying to pump against a CLOSED valve.


So I can't figuire out why it is possible for it to do what you are saying it's doing.

AD

Ok I checked the switch today. I started the truck on the front tank. It was running fine. then I shut it off and switched to the rear tank. It started and stopped immediately.

It started on the residual pressure in the fuel system.

Try switching the switch with the engine running.

I do that all the time on my truck.

Unless you are accelerating hard, you'd never know you switched tanks.

I think you've got a problem with the rear pump.



AD

Rockauto.com might have one

Ok I did what you said and the engine ran for a few seconds. it started to flare up and down on rpms and then it dies. I switched it back over and it worked fine then I switched back and it eventually drained the battery. it would start flare in rpms and promptly die. what the heck is wrong with this thing?

F84R said:

Ok I did what you said and the engine ran for a few seconds. it started to flare up and down on rpms and then it dies. I switched it back over and it worked fine then I switched back and it eventually drained the battery. it would start flare in rpms and promptly die. what the heck is wrong with this thing?

Click to expand...

What part of: I think you've got a problem with the rear pump.
did you not understand from my last post?

I also said the bit it runs when the rear tank is selected
is "Residual pressure" in the system from when you were
running it on the front pump.

What possessed you to keep attempting to run it on the rear pump for more than a test to the point where you ran the battery down?
I only asked you to do that to confirm the diagnosis because I didn't understand the point of shutting the engine off before switching tanks as you said you did when testing the rear pump.

My guess is that your rear fuel pump is as dead as Julius Caesar.

You can positively confirm this by cycling the key to "on" (DO NOT CRANK THE ENGINE) and listen to the fuel pumps run for
the few seconds.

Don't be confused by the sound of the frame mounted pump running....
Try this with each tank selected, you might want to have a friend turn the key while you listen from UNDER the truck.
It's pretty easy to hear the in-tank pumps run though
they are generally fairly quiet when compared to the later high-pressure intank pumps.

AD

AD

IDK. I didn't even think about it draining my battery. but it could also be the valve correct? you said that if the pump was trying to pump through a closed valve the engine would die. So until I check the status of the pump I can assume that either one could be bad.

ok. it didn't drain my battery. I am not getting fuel to the engine now. I am in the process of replacing the hi/low pumps. i checked the inertia switch. It was fine. but I just realized it could also be my relay. Does anyone know which one it is? neither pump is working and listened for the pumps. and nothing. my truck was not starting. I will have the tank back in tomorrow. Any ideas as to what might have happened?