Dual Tanks after 4.0 Swap

Hitchner2009 · May 2, 2016

So another good question, I had dual tanks on my 87 2.9 before i swapped the 4.0 into it. Has anybody figured out a way to wire in the dual tanks with the 4.0 harness? I have looked over the schematic but its a little difficult to read, i cant find a D&O anywhere for the tanks, otherwise i could rig something up. I have the switch on the dash and everything, just no way to get power back to the pump in the rear(2nd tank).

RonD · May 2, 2016

1987 should still have the one high pressure pump in the frame rail.
Then one lift pump in each fuel tank.

There would be a 6 port fuel line solenoid near that high pressure pump.
2 fuel lines from engine, 1 line passes thru the high pressure pump
2 fuel lines from front tank
2 fuel lines from back tank

The switch on the dash changes in-tank sender connection(fuel level), and Lift pump power connection.
It also sends out 0 volts or 12volts to 6 port solenoid to switch fuel lines.

4.0l wiring should not have changed any of that

One reason you don't see dual tanks much any more is because of the expense of adding a second EVAP system, surprised a 1987 even had dual tanks from factory

adsm08 · May 2, 2016

Well, that's not the only reason you don't see dual tanks. There is the failed diverter valves, the sludging of an unused tank, space concerns.

Overall it is much easier and more reliable to just put a single 38 or 40 gallon tank in (Some F150s have an optional 38 gallon tank, don't park them on a hill below 1/4 full) than to have a dual tank system.

But yeah, the 4.0 shouldn't effect anything. Aside from the physical location of the pump relay and a few adaptors I had to make to connect things the fuel systems in both of mine are stock, wiring and all.

AllanD · May 16, 2016

Actually the factory dual tank wiring doesn't run power to the rear tank exactly...

The selector valve switches power between the two tanks...

How did you wire in the 4.0? because on my '87 the 4.0 swap didn't affect the dual tank wiring? Did you do a "dash swap" to accomplish your swap?

I did the swap with the '87 dash...

AllanD

Dual Tanks after 4.0 Swap

Hitchner2009

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