Question for fuel sending unit experts

Evan · Jan 16, 2009

I recently purchased and installed a 20 gallon aluminum fuel cell. It came with a 0-90 ohm sending unit. I connected the two fuel gauge wires to the two leads on the tank sending unit. When topped off, the gauge reads a totally empty tank, which means 0 ohms of resistance between the two poles. The tank is about half full now, and the needle is still on E; it hasn't moved. It I disconnect one of the wires the gauge goes up past full.

Has anyone had experience with connecting "foreign" fuel sending units to stock RBV gauges? What do I need to do to get this to work?

martin · Jan 16, 2009

the stock gauge reads relative to ground.

Evan · Jan 16, 2009

martin said:
the stock gauge reads relative to ground.

How would I hook that up? There were 4 wires in the harness total. 2 obviously powered the pump, so that left me with two wires that I assumed were for the gauge. And there are two leads on the sending unit. The resistance between those changes as the level changes. So do I need to ground one of the leads?

timster · Jan 16, 2009

take one of the wires and attach it to a ground point such as the frame or body

shadetree · Jan 17, 2009

Did you reverse the two wires you are using going to the sending unit?
The new tank is metal so the sending unit will ground thru the tank to frame more than likely. You can use your meter to see if the tank is grounded. If so, find the hot wire from the gauge and put it on the terminal that makes the gauge read. I don't know if 90 ohms is enough, but it should give you some kind of reading.

shady

timster · Jan 17, 2009

yeah it should ground through the tank, I had to add a direct ground on my bronco, when I upgraded to a single pump and plastic tank. I thought I would toss it out there, incase he is using rubber on the straps, and points where it touches the body/frame.

Evan · Jan 18, 2009

I messed around with it this afternoon, and can't get it to work.

There are two terminals on the sending unit. A center post and another terminal on the side which looks to be grounded to the tank. I verified the tank is grounded.

Right now I have the "positive" from the fuel gauge attached to the center post on the sending unit. And the other lead from the gauge is grounded. The gauge is dead on E, with a full tank. If I disconnect either lead, the gauge goes to F, even if it's empty.

Here's what my sending unit looks like:

Question for fuel sending unit experts

Evan

15+ Year Member

martin

15+ Year Member

Evan

15+ Year Member

timster

15+ Year Member

shadetree

15+ Year Member

timster

15+ Year Member

Evan

15+ Year Member

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