Subford, thanks for the information. Can you tell me how the tank pumps are grounded? Had time today to do some poking around. I have the dash panel off and the selector switch hanging out ready to check with a meter next time it happens. Looks to me like the power comes from the pump relay to the center of the one side of the switch on a red wire w/yellow stripe, and goes out to rear pump on brown/white stripe. I know that the tank connector has 2 terminals for the pump. Where do they ground the motor? When it happens again, I can watch and see if there are volts going to the motor. If so, then it's either in the wiring, or it's the pump.

I'm still wondering why this didn't happen with the leaky front tank still there.

Thanks
Craig

 

The fuel pumps are ground at ground point 801.
Ground 801 is located at the LH (drivers side) inner fender behind the headlamp.
Not sure why I have G203 in the diagram below.



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Thank You. A picture is worth a 1000 words. That should really help me follow things around.

Craig

 

hey whisker subford is the expert on the dual function reservoir, but from his diagrams i have seen the insides of two of these parts and one of them was just this week after i retrieved it out of a junk yard for $5 yes i said $5 i got lucky they didn't know what it was. i told them it was a fuel filter. I think you might have a problem on the return because of the thickness of the bio diesel without being heated has a very small hole to go through. i say this because when I was cleaning out the rust on my first one with PB it was slow to come out of the return line that goes into the cap and back through to your tank. my suggestion would be to heat on both sides and flush it out with diesel. If you haven't seen the inside of one the hole is the size of a coffee stir stick. very small. that might be the only problem you face inside this part.

 

calvery24,

I think you are talking about a device that he does not have.
You are talking about the valve for a gas truck or van that is fuel driven with no wires.
He has motor driven fuel valve that has wires going to it.

 

I have a 1986 XLT F150 4X4 dual tanks. I had a problem with my rear tank three years ago thought it was the Dual Function Reservoir. I un hooked the lines from the rear tank to the reservoir. Now my front tank is doing the same think sputtering when you try push down too much on gas. I took the reservoir off and it only has four lines to it. I took it and opened it up thought I would find a filter. I put the air hose to it and lines were clear. Now what? Should I just buy a new one?

 

Do you have two not connected ports on the a selector valve that went to the rear tank or has it been replaced with a single tank reservoir?
If it is a single tank reservoir I would say you have a bad front tank pump or bad wiring (power) to it.

 

It is the resevor that was on the truck when I got it. It has four ports. The two hose from rear tank conected to the hoses from the front tank.

 

Does not sound stock.
Sounds like some modified it to run both tank at the same time using a single tank reservoir.
They would have also rewired the wiring to run both in-tank pumps at the same time.

 

Subford,

I read the first 11 pages and didnt find a problem like mine.
I am having a couple problems with my (new to me) 1986 460 with dual tanks.

1) I have to shut truck off to switch tanks(cant do it on the fly) switch will move, it just wont draw from other tank till shut off and restart.
2) Gauge reads empty on rear, full on front.

Truck actually runs and operates fine minus those problems.
Previous owner installed a mechanical fuel pump said something about having issues with intank pumps. I dont know if the pumps are still in tank, hooked up, un hooked etc.

I, more than anything, just want my gauges to work, i figured maybe bad sender but wondering if it might be the valve?

Dan

 

RockWVU,
As you know the selector valve changes the gauge from one tank to the other.
I would guess that the pumps are still in the tanks and the engine mounted fuel pump can pull fuel through the electric in-tank pumps. I know as I have kinda did the same thing with a 460. I would turn the in-tank pumps on with a switch if I needed them for going up steep hills, I have driven thousands of miles this way.

I would have no idea what he may have did to the wiring of this fuel system. Also I can not come up with why you would have to turn off the engine to change tanks.

 

any thoughts as to the fuel gauge? i just looked at my valve, it is 6port, all the connections look factory as far as the wiring as much as i could see looks stock. I'm wondering if the mechanical pump has to shut off to allow the tanks to switch is my only theory.

 

The selector valve is motor driven and the engine mounted pump not could not stop the motor from running.

When you say the gauge reads full on one and empty on the other do you mean the pointer points at "E" & "F" or does the pointer peg at each end of the gauge.

 

definitely pegs empty on rear, on the front, i'm not totally sure, but i think it reads above full

 

Sounds like the gauge wire going to the front tank is open and the wire going to the rear tank is shorted to ground between the selector valve and the tanks.