Fuel send unit and gauge issue

[Banana]

I'm joining the thread now unfortunately. Been trying some, but not all of the suggestions so far.

I haven't take out the sending unit out yet for inspection. Just put it in 2 years ago with a brand new tank. Of course doesn't mean it didn't already go bad.

I'm trying first to rule out the Rally Fuel Gauge. I thought I read in other troubleshooting guides is that if you take off the blue wire on the gauge, i is supposed to peg to full. Didn't happen on mine. So not sure how to check the gauge while still installed in the gauge cluster and IP.  By the way the gauge is original to the car.

The other check I have is with the blue wire off the sending unit, the gauge pegs to full left. I checked the Ohms on the sending unit and I get about 26 Ohms which I hope means there is at least 1/4 tank. Then taking off the blue wire the gauge moves up slightly, but stays under E.

So, do I now remove/inspect/replace the sending unit as next step?  Can I rule out broken gauge ?

Any advice appreciated

[Banana]

Please note top picture is "blue wire on sending unit", bottom picture is "blue wire off sending unit". 

[JS29]

@Banana  You ground out the wire at the tank, and the gauge will read full max to check the dash gauge. 

[MoparLeo]

The information is on this site. Look at the resources section for more good info.
https://www.youtube.com/watch?v=-pKbNSStjas

[Banana]

Thanks Guys, will follow Cody's troubleshooting steps. My bad for not checking the awesome resources section first !!

[DeathProofCuda]

@Banana  You ground out the wire at the tank, and the gauge will read full max to check the dash gauge. 

@Banana

JS29 is correct, but you only want to ground out the sending unit for a couple of seconds.  If you leave it connected longer than that you can burn out the delicate wiring in your fuel gauge.

Try this:
- Have someone else sitting in the car with the key turned to the "run" position
- Run a length of small diameter jumper wire (like 18 gauge) from the negative side of the battery to the back of the car, near the gas tank sending unit.
- Remove the sending unit wire connection from the tank and connect the jumper wire to the sending unit wire, but just for a few seconds
- If your gauge is working properly, your helper in the car should see the fuel gauge sweep up to Full when the wire is connected

If you have your fuel tank sending unit out, or have a spare one, you can connect it in between the sending unit wire and the jumper wire and then test the gauge function throughout the sweep of the sending unit arm.

[Banana]

@DPC

I did ground the Blue Sending Unit wire to ground. The Gauge did rise up and almost hit the F mark.

It actually took about 10 seconds to go from E to almost F. Didn't push it past F to prevent Gauge damage.

Question:
- The needle was really herky-jerky going from E to F. Not smooth rise at all.  At least 10 seconds before getting to F.  Is this a normal gauge reaction? Or the gauge should move smoothly?

In the meantime I'll pull the sending unit for inspection.

Thanks

[DeathProofCuda]

@Banana

Sorry, didn't see this previously.  @DPC won't work to tag me.

My gauges move fairly smoothly, but I am running an upgraded instrument panel voltage regulator.  The old school IPVRs use a bi-metal strip to continually pulse a 12 volt feed so that your gauges only see an average input of about 5 volts.  If you are running an original style IPVR than I'd guess that herky-jerky could be pretty normal.  Maybe someone else still running an original IPVR can chime in.

At this point, I'd be taking a harder look at the sending unit.  You might want to try running a separate ground connection between your battery ground and your sending unit.  If the sending unit doesn't have a good ground connection, the gauge won't read correctly.