56mulberry

did a bunch of searching on dual tanks issues for our 87 f150. Tekk me if you agree with my diagnosis before I go buy parts....

Here is waht it does:
FACT#1:
Dash switch on front tank=gauge works fine, truck runs fine
Dash switch on rear tank= gauge always read Empty and truck quits like out of gas

FACT #2:
Can fill front tank normally when empty, rear tank will not fill--acts like always FULL when try to pump gas into it.

My thots: sending unit in rear tank bad (hence always on "E") and diverter switch bad between tanks (NOT dash switch--the one under truck between tanks) So rear tank is actually full but cant pull gas from it due to bad diverter switch and sending unit reading E becuse it bad also....

Question? Dash switch is independent of diverter as far as reading full/empty but MUST work to make it divert from rear tank....?

Sound reasonable? D

56mulberry

OK on second thot--after some more readinf about low pressure in tank pumps (if I have one?) I think best bet would be to change the rear tank sending unit FIRST and see if that allows diverter to work correctly? If not then I know diverter is bad also?

Suppose way to check this would be to swap supply line for front and rear and see if it allows diverter to work right whne switching dash switch from front to rear....while gauge should still read empty due to bad sending unit.?

Could rule out diverter that way I guess..? .D

IF needs SU in tank will kind of suck because tank is completely full and might be easier to lift that side of bed and do from above--thats what I did on my Chev 1500....D

ymeski56

Sounds like the rear L/P rear pump & sender, but simultaneous failure gives pause for thought. I'd check for power out of the dash switch to make sure your getting power out to each pump when switch is in the proper position for that pump/sender activation.

The diverter is mechanical, relying on the L/P pump to actuate. They occasionally develop an inner o-ring problem that does not allow the diverter to switch .http://www.stangler.com/motorsports/...alve/index.htm

A weak pump tends to cross fill. Disconnect the line out from the rear & see if you get flow. Two people procedure w/ a gas can.

56mulberry

I am thinking L/P pump in rear tank also because the gauge reads "E" when I switch to that tank also even though it is full--now that I see diverter is purely mechanical and just a diaghragm activated by pressure it would make sense that either rear pump/SendUnit is bad or perhaps not getting power supply--gonna check hot/ground to it and if good will know its the unit. D

1987 F-150 XLT 4x4

I agree with ^ on the rear tank low pressure Fuel Pump and Sending Unit being the problem with your truck.

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To make your own portable fuel pumping device to pump gasoline from the rear tank to the front tank.

Purchase the list below:

One (old type) 12V Fuel Pump with 3/8" suction and 3/8”discharge.

8-10 feet of 3/8" Fuel Hose

Two 3/8" hose Clamps for attaching fuel hoses to fuel pump.

One 20 amp Toggle Switch

4 feet of 12 AWG electrical wire for ground wire and
4 feet of 12 AWG electrical wire for Positive/Hot wire (Cut in half for the switch)

Two small Clamps for attaching to battery posts
(Red/Positive and Black/Negative Clamps)
----------------------------------------------------------------------------------------------------
Cut the fuel hose in half,
attach one hose to the fuel pump inlet
attach the other hose to the fuel pump outlet

Connect wires, small battery clamps and toggle switch to fuel pump

Put the Suction hose of the fuel pump into rear gas tank and
put the Discharge hose of the fuel pump into front gas tank if it is near empty or
into several 5-gallon gas cans.

You will need a small battery to energize your new portable 12V fuel pump.
A riding lawn mower battery will work fine.
----------------------------------------------------------------------------------------------------------

DO NOT LEAVE FUEL PUMP UNATTENDED WHILE GASOLINE IS PUMPING!


See Picture of mine, I used 12V wires that I already had, so it's not "purty"

techrep

iTrader: (1)

Just take the bed off and you can do all your work without having to drain the tanks...you can change the diverter and then op check it before you put the bed back on...if the pump needs replaced your already there...either way its easier then draining and dropping the tanks...trust me been there done that...good luck

Just call me Sean

iTrader: (1)

It's not hard to drop a tank, even if it's full. Taking off the bed is a pain in the ***.