Fuel Gauge Troubleshooting

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David Discenza

Hello! New member and first time Catalina owner.
We just took possession of a 1993 C34. During the seat trial, the fuel gauge was working. Now that I own the boat, it's not. I've done some preliminary troubleshooting with these results:
- I checked the voltage with mu multimeter at the instrument and it read 12.5 volts, same as the battery meter.
- I disconnected the sender wire and used a screwdriver blade to short across the sender input post and the ground post. The needled jumped to the 1/2 position on the gauge.
- I checked the resistance of the sending wire at the instrument. It read zero ohms at all settings of my multimeter
- I checked the resistance of the sending wire at the fuel tank. It read zero ohms at all settings of my multimeter

The needle of the gauge is all the way to the left, off the scale of the gauge. When I turn the ignition key, the needle jumps a millimeter or two and goes right back to all the way to the left, off the scale of the gauge.

I want to see if the repair shop at my marina has a fuel gauge that's known to be good. If they do, I'll temporarily connect it and see if it works. If it does, then it's definitely the gauge. If it doesn't could it be the sender as well as the gauge?  I'd appreciate the thoughts of others on this problem. Thanks to all who reply.
CTYP12441293
"Irish Lady"

Ron Hill

David : A while back I put the Teleflex and Seaward fuel gage trouble shooting steps on this Message Board.  They maybe in WiKi?

A thought
Ron, Apache #788

David Discenza

CTYP12441293
"Irish Lady"

KWKloeber

David,

Welcome to the CTY family.

I had put the gauge t/s guide in the engine > electrical wiki topic. 
http://c34.org/wiki/images/3/34/Gauge_Troubleshooting_Steps.pdf
It gives the resistances of the fuel sender so you can check it at empty and full . 
Float empty the R should be about 240 ohms.  Full, the R should be about 33 ohms.

See below:

Quote

- I checked the voltage with mu multimeter at the instrument and it read 12.5 volts, same as the battery meter.
- I disconnected the sender wire and used a screwdriver blade to short across the sender input post and the ground post. The needled jumped to the 1/2 position on the gauge.


If you ground the S terminal on the gauge it should pin high. Your gauge is toast (caveat - based on your test.)
If you disconnect the sender wire the gauge should pin low.



Quote

- I checked the resistance of the sending wire at the instrument. It read zero ohms at all settings of my multimeter
- I checked the resistance of the sending wire at the fuel tank. It read zero ohms at all settings of my multimeter


Checked ohms from sender to tank body, I presume?  Or to ground?
Make sure the tank bond wire is intact and low resistance tank to battery negative -- or take your ohm reading to a known good battery negative location.


Quote

The needle of the gauge is all the way to the left, off the scale of the gauge. When I turn the ignition key, the needle jumps a millimeter or two and goes right back to all the way to the left, off the scale of the gauge.


With the gauge way left (zero-ish) it indicates that there is infinite resistance in the S circuit.  In other words a disconnected S wire.  It doesn't make sense that the float reads 0.0 ohms -- then the gauge should be reading right (way high-ish.)
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
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mainesail

#4
This article can help you in testing the sender.

https://marinehowto.com/testing-a-marine-fuel-sender/
-Maine Sail
Casco Bay, ME
Boat - CS-36T

https://marinehowto.com/