Fuel pump plumbing questions.

[Laguna]

I just finished replacing the fuel tank selector valve thingy, as it was broken when I bought the truck. Theres two fuel lines going to the front of the truck, which I'm assumign are the feed "to engine" and return "from engine" lines.

My question is, which line goes where on the fuel pump?

When I got the truck it was plumbed to take gas from only the driver side tank (auxilary?) and it went straight to the fuel pump. The other inlet on the fuel pump was just plugged off. Which little inlet on the fuel pump to I plug the 'to engine' and 'from engine' lines to?

Heres a little picture (sorry for the bad quality, camera phone) to maybe better get accross what I'm trying to say.


The fuel line plugged into the fuel pump right now is soft and easu to squish with your hands, where as the line that is capped off and just sitting there in the bottom of the picture is full of what I assume is fuel. Becuase of that I'm quite certain the line that is currently capped off is to 'to engine', but which little plug does it go to?

[piecesparts]

On my truck the supply fuel line inlet was the bigger line, and the return was a small 1/4" line and the fuel pump had a small orifice drilled into it's outlet that feeds it. If you want to know which is which, blow air through the lines on the frame and the return should be higher up in the tank than the suction line. Careful that you don't blow to hard, or you will blow the sock off of the inlet to the suction line. The one you reference as being full of fuel is probably the fuel supply line, but try to siphon fuel out of the other one to see.

[Laguna]

I hooked the lines up to the fuel pump, and theres no fuel getting to the pump. I tried changing them around at the pump and at the valve, but still no fuel getting to the pump. Wehn I put the new switch in the truck was running and taking fuel from the drivers side tank. Then I switch the tanks to the empty one and the truck died (passengar side tank is empty). But now I cant get the truck to switch back to the drivers side tank, and I filled up the passengar side tank and theres still no fuel getting to the fuel pump.

[boxrodz]

Laguna -
Have you made any progress on your problem?

[Laguna]

Well I spent awhile trying to get the valve to work. I got it to switch from the driver side tank to the passenagr side tank, and the truck died becuase that tank was empty. However, I cant get it to switch back to the drive side tank, so I connect the driver side tank directly to the fuel pump.

This allowed me to drive my truck, however I left the return line hooked up to the selector valve, which is stuck on the passenagr side tank. So, I ran out of gas pretty quickly becuase all the gas was being drawn from the driver side tank, and returned to the lassenagr side tank.

I plugged the return outlet off the fuel pump (like it was when I bought the truck) and left the driver side tnak hooked up directly to the fuel pump. But, now theres a bunch of fuel leaks from the fuel pump where the lines plug into it. Mainly just the return line is leaking away, I've got a plug on the outlet and a bunch of hose clamps tightened down, but fuel still drips out.

[boxrodz]

I assume your fuel tank selector valve is new (or functioning correctly). If so, it sounds like you may have a bad switch. From a previous post, the wiring schematic for the fuel tank selector system is shown below:



It sounds like your auxilary tank selection is working properly (i.e. when switched, the dark green wire applies +12 V to the valve while the light green is grounded). If you momentary reverse the polarity of the two, you should be able to revert the valve to the production tank.

In the meantime, you probably need to route (plumb) your overflow over to the production tank instead of capping it off.

[Laguna]

When I select the aux. tank with the switch, theres only about 3V of power getting to the tank selector valve, should it be a full 12V going through?

Is there a way to test if the switch is the problem, or just replace it and hope for the best?

[boxrodz]

Originally Posted by Laguna

When I select the aux. tank with the switch, theres only about 3V of power getting to the tank selector valve, should it be a full 12V going through?

Do you actually mean the production (driver-side) tank? Regardless, you should have at least +12V between the light green and dark green wires (with the ignition switched on). It makes me wonder if you have a wiring problem or a switch problem...?

Originally Posted by Laguna

Is there a way to test if the switch is the problem, or just replace it and hope for the best?

Check the voltage level of each of the wires (light green and dark green) when you select the Auxiliary tank. Then do the same for the Production tank. Switching to the Auxiliary tank, the +12V reading should be observed with dark green wire (+) and the light green wire (-). Switching to the Production tank, the +12V reading should be observed with dark green wire (-) and the light green wire (+). Check these readings at the selector valve then at the switch. Then check to be sure that the 12V (ignition-switched) source and ground feeding the switch is good. If the 12V switched source/ground is good, but you get abnormal readings coming from the switch, I'd say the switch has gone south. I don't know if it can be disassembled and repaired.

[Laguna]

When I check the voltage on the wires, you need to hold the switch down pretty ahrd and wiggle the thing around and you usully get 12 volts going through the dark green wire, but never any power going through the light green one.