Gas gauge not right

[bump]

Working on a 2005 FLTHCI, the fuel gauge reads full when on jiffy stand, stand bike upright and fuel gauge goes to empty. Gauge does this when engine running or not. I think it is in sending unit, going to pull fuel pump out of tank and check it out. Anything to look for that is not standing out?

[smoserx1]

That would be my guess.  It looks like the sending unit mounts to the pump body with a screw.  Anyway once out of the tank check the resistance of the lead(s) with an ohmmeter as you move the float up and down.  The resistance should change smoothly.  My FLHT is carbureted and I have replaced my sending unit a bunch, but now  they are ridiculously expensive.  I read somewhere you might be able to repair one simply by cleaning up where the contact rubs along the resistor wire and that sort of makes sense.  I'm sure ethanol and old gas will gum up these  just like other parts of the fuel system, so maybe you will be able to salvage it without having to spend a fortune on a new one.

[bump]

Pulled fuel pump and sending unit out. Saw nothing obvious wrong. With multimeter I can get varying reading by moving float up and down slowly. Gauge on dash moves with movement of float and low fuel light goes out. Put it all back together and fuel gauge won't work and low fuel light stays on. I am getting 12 volts to fuel pump and sending unit but gauge not reading. Looking in factory manual and electrical manual but not finding much. Anybody have any suggestions?

[kd]

Did you check it for float saturation?

[bump]

The float doesn't seem to be saturated but I will look at it closer. I can get gauge to work out of tank. Gauge goes up and down with slow movement of float, low level light works also. Must not be getting it in tank right. Also getting a couple codes  that need looking into.

[Breeze]

I remember the manual referencing a "detent" in the arm that makes getting the unit back into the tank. Did you release the arm from the detent position after getting it in?

[Geezer_Glider]

Don't have the schematic here at work, but doesn't the sender run on a regulated 5V source, not 12V? Also the contactors in the sender can be sensitive to slight side loading of the float arm.
R Meyer

[MBrown]

Having some fuel in the tank can help when installing the assembly. I've see the float get bound up when tank is empty.

[Geezer_Glider]

Checked the manual last night, I was wrong, 12V to sender.
Sorry,
R Meyer

[bump]

12v sender is not showing resistance correct range 03 to 35. I think the range should be like 30 to 200.

Manual says range should be 7 to 95 ohms. Getting higher readings all over range of float arm.
Cleaned switch at float arm and didn't help.

[kd]

Ground circuit connection?

[smoserx1]

Try this:  Now that the sending unit is out, identify the mating contacts for the connector going to the bike's gauge and with the ignition switch on jump the two connectors together (make sure you identify the ones just to the gauge, not the fuel pump).  This should send the full 12V to the gauge and it should move from empty to full.  The needle movement should be smooth and not too fast (it should not slam against the full side stop).  If this passes based on what you have already diagnosed it is almost certainly a bad sending unit.

[bump]

Try this:  Now that the sending unit is out, identify the mating contacts for the connector going to the bike's gauge and with the ignition switch on jump the two connectors together (make sure you identify the ones just to the gauge, not the fuel pump).  This should send the full 12V to the gauge and it should move from empty to full.  The needle movement should be smooth and not too fast (it should not slam against the full side stop).  If this passes based on what you have already diagnosed it is almost certainly a bad sending unit.

After much research and wire tracing I discovered that the fuel level is 5-7 volts fed from the ECM to speedo to sender. I checked the sender ohms and am getting readings wat out of range. Sender should have 7-95 ohms according to electric manual. I am starting to look for new sending unit.
Fuel pump is 12v.

[bump]

Put pump back in and filled with 1.5 gal gas then took it for a ride. gas gauge seems to be working now. Only went about 15 miles so will try it for awhile.

Thanks for the help 

[BrownsfaninMN]

...I just got finished with the same problem on my 2004 FLHT, look at the metal locking (non-threaded) nut on the float swivel, ensure that is pushed on all the way, mine was.  Thought it was the float sending unit, replaced it, put her all back together and as soon as I started the bike to move it in the garage the gauge went to full (...needless to  say I put the old float assy back in).  Bought a new gauge (off ebay) and installed, whatdayaknow, it was the gauge, no problems since.