Fuel gauge

Okay - what controls the fuel gauge on an R1150RT?

Is it the float thingie, or is it that 'sending unit' that has the electrical connection that attaches to the fuel pump plate?

Just replaced the fuel pump, and filter, and vent lines, and not the fuel gauge is maxed out...as in shows REALLY full.

float thingie = idiot light

sending unit = fuel gauge

Grazie...The yellow wire coming from the sending unit has NO insulation remaining on it, and the ground wire is pretty bad.

Okay - what controls the fuel gauge on an R1150RT?

Is it the float thingie, or is it that 'sending unit' that has the electrical connection that attaches to the fuel pump plate?

 

Just replaced the fuel pump, and filter, and vent lines, and not the fuel gauge is maxed out...as in shows REALLY full.

I presume you mean "now" instead of "not".

The float connects to an arm that rotates, causing a contact to sweep wires wound around an armature. This is called rheostat.

Sweeper at one end, low fuel level; at other end, high fuel level.

Apparently, the float arm is stuck.

Okay - what controls the fuel gauge on an R1150RT?

Is it the float thingie, or is it that 'sending unit' that has the electrical connection that attaches to the fuel pump plate?

 

Just replaced the fuel pump, and filter, and vent lines, and now the fuel gauge is maxed out...as in shows REALLY full.

Morning Flars

Your 1150RT has 2 separate fuel level monitors. One is for the low fuel light (only) & that is that float on an arm that acts like a switch to light the dash light to show when you are low on fuel.

The other is the actual fuel level sender, that is the long tube with a float inside it that runs up & down on 2 resistor wires. This is the sender that registers the fuel level on the fuel gauge. This is the one that plugs into the back of the fuel pump pass through

Though they act independently both the low fuel (float/ on/ an/ arm) & the long sender (tube) do share some common connections.

If you inverted the tank with the float tube still in place then sometimes the float will stick at the top due to gunk & varnish in the tube and/or on the float. OR, the float tube might have a dent in it (from a faulty tank venting system sucking the tank sides in) & sometimes the float will stick above the tube dent. OR, you could have a short in the wiring somewhere between the float tube & the fuel gauge (open = low fuel level___ short = dash gauge reading full)

DR - that is what I figured. The wires that plug into the fuel pump pass through are completely bare - the insulation is just GONE on the yellow wire and barely hanging in there on the ground wire. Since the fitting is not sealed, it seems like there would be a continuous short even if the insulation was intact, since I am pretty sure gasoline is conductive.

I did, indeed, have the tank upside down, so maybe the sending unit float is stuck.

Is normal wire 'fuel resistant' ?

Afternoon Flars

The wires that plug into the fuel pump pass through are completely bare - the insulation is just GONE on the yellow wire and barely hanging in there on the ground wire. --Yes, you probably need to replace the wires or at least cover them with small diameter fuel resistant hose.

Since the fitting is not sealed, it seems like there would be a continuous short even if the insulation was intact, since I am pretty sure gasoline is conductive.--Gasoline or even E-10 is not conductive enough to effect the fuel gauge operation. Bare wires will actually work OK as long as they don't touch each other or touch another conductive item.

I did, indeed, have the tank upside down, so maybe the sending unit float is stuck.--Very possible a sticking float, or possibly you have a short between the wires running from the pass through to the float tube.

Is normal wire 'fuel resistant' ?-- Most (standard) electrical wire isn't very fuel resistant (well the wire is but the insulation isn't).

Thanks again.

If you pull the fuel gauge tube, be careful as the resistance measuring wires are about the thickness of a hair and can break easily. Check to see that the tube doesn't have a kink in it. I straightened mine out, re soldered the wire I broke from its attachment point , reassembled ,and it has worked flawlessly for years and thousands of miles. Do you feel a suction when you lift your gas cap ?. If so , that indicates a condition that could crush the fuel gauge tube.

If you pull the fuel gauge tube, be careful as the resistance measuring wires are about the thickness of a hair and can break easily. Check to see that the tube doesn't have a kink in it. I straightened mine out, re soldered the wire I broke from its attachment point , reassembled ,and it has worked flawlessly for years and thousands of miles. Do you feel a suction when you lift your gas cap ?. If so , that indicates a condition that could crush the fuel gauge tube.

The fuel gauge decided to fix itself after a few bumps and thumps, but of course that doesn't mean it won't 'un-fix' itself sometime in the future.

Is the system here the same for a 1996 R1100RT?   Mine reads around 2/3 when completely full.  (just got it a few weeks ago...new here...Thanks!)

2 minutes ago, Flexmoney said:

Is the system here the same for a 1996 R1100RT?   Mine reads around 2/3 when completely full.  (just got it a few weeks ago...new here...Thanks!)

Afternoon  Flexmoney

Yes, the 1100RT is very similar to the above 1150RT  mentioned.

If you need help to diagnose 'your 1100RT' then please start a new thread on your 1100RT gauge issue so it doesn't get confused with the original posters problem here & hijack this thread.

Thanks for the confirmation.  If needed, I'll start a fresh thread.