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Potential problem with fuel senders

B

bob888

Well Known Member
I have the Vans standard fuel senders and went out to calibrate the fuel tanks today using the G3X procedure. With zero fuel, I got 11.998 v. on both tanks. With 5 gal of fuel, I got 11.998 v. on both tanks. I stopped there because if the senders have to come out, I don't want to drain 30 gal of gas. This could get ugly unless someone out there has a good idea about why these are both apparently stuck. When I installed them, both moved freely and were clear of the vent tubing as far as I could tell. Advice welcome...
 
It almost looks like the bias resistor is not installed.??
You also get the same symptom if the fuel sender is not grounded.
 
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Thanks for jumping in Bob. However, I think this sender is grounded through the frame as far as I can tell. Also, no bias resistor shown on the G3X wiring schematic...unless I'm missing it? If you have more insight I'd love to hear it.
 
The way these things work (they read voltage) you must have a bias resistor in series with the 12 volts. I know older boxes needed an external resistor; some (I know GRT) newer boxes have an internal bias resistor, but you must "insert" it in a set up menu.
Your Garmin manual must have this setup somewhere.
 
The sender is grounded thru the screws that hold the cover plate on. I put a lot of sealant on those screws so I ran a strap from one screw to a good ground, just to be sure.
 
Are you using the GSU 73 module? If so,
The fuel senders go to pins 25 and 64, with other end grounded locally
Pins 5, 44, and xx (ground) all tied together
Pins 76, 77, and 58 all tied together. This is the 10 volt supply to internal bias resistors.
 
I have seen these stick before. One way that worked to unstick them is to out enough fuel in to break it loose, and also to rock back and forth to slouch the fuel inside the tank to break them loose. First make sure you have them wired correctly. Both giving the exact same reading would tell me it's not a stuck float, unless maybe both are stuck in the up position.
 
BobTurner said:
Are you using the GSU 73 module? If so,
The fuel senders go to pins 25 and 64, with other end grounded locally
Pins 5, 44, and xx (ground) all tied together
Pins 76, 77, and 58 all tied together. This is the 10 volt supply to internal bias resistors.
Click to expand...

Not sure what you mean by "pins 25 and 64, with other end grounded locally". In my installation using the harness built by Stein, IAW with the GSU 73 sensor wiring example, my senders aren't grounded locally. They are grounded back to pins 5 and 44 and the XX signal ground.

I would also recommend besides insuring you have a good ground to the cover plate, that you make sure that the signal wire that attaches to the center screw isn't grounding -- IIRC there should be a fiber washer between the connector and the unit.
 
Set the senders to read resistive not voltage, on the the configuration page!

You have 3 choices......resistive, voltage, and frequency. I suspect you have chosen voltage.
 
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