Fuel Gauge

[OregonCoaster]

Morning All, what’s
We have a 1989 Gulf 32 Pilothouse. Fuel gauge appears inoperable and we are trying to troubleshoot based on what we found so far we should see 3 wires (black, blue, & yellow?) yellow is 12V, black is ground, and blue is sending wire?

In ours it appears we have 2 of each connected to same point. Not sure where to go from here. Any help much appreciated!

Pics attaced

[donradcliffe]

https://www.boatingmag.com/story/how...ts-fuel-gauge/

[OregonCoaster]

Thank you Don,
Just used a meter to check gauge positive and ground and reading is coming up 8.5…not 12. Does this immediately indicate a bad gauge?

[donradcliffe]

Not necessarily. The picture is hard to see, but it looks like the yellow is positive, the black is ground, and the blue may be a lighting wire. The signal could be the post marked 24, and I can't tell its color, but it should be pink. The black, yellow, and black wires are daisy chained to other gauges. If the voltage between yellow and black is only 8, the ignition wire switch/connections could be dodgy, or one of the other gauges could be pulling down the supply voltage. You might try jumpering the 24 wire to ground and seeing if the gauge goes to full. You could also check the voltage between yellow and black at other gauges., You could also isolate this gauge from the daisy chain.

[OregonCoaster]

Cool okay. Two yellows, 2 blacks. Daisy chain makes sense and I thought perhaps that’s what it was but good to have reassurance. Two blues..I was ignoring those but lighting you say? Is that necessary foe the gauge then perhaps? The 4th wire is red (assuming this is the pink sender), there’s only one of those.

Correction to earlier post the 8.5 reading was actually coming up between ground and sender. Between yellow and ground I’m getting 11.4V.

Article mentions alligator clips and a jumper wire but not sure I have those available? I guess question is what is the procedure for “jumpering”?
Thank you!

[GordMay]

Basic Engine Gauge Theory and Testing
➥ https://www.cruisersforum.com/forums....html#post2597

[OregonCoaster]

Ok , just pulled sensor from tank and it was completely dunked and corroded. Arm could barely move. Found the spare in photos aboard boat. Couple things, only found 1 red wire connected to top of sensor, no black/ground wire. Then, this new sensor appears to have two pink wires coming up to two connection points. One says “S” and one says “—“

[donradcliffe]

The poor man's jumper is simply a piece of wire with both ends stripped. Touch one end to the sensor terminal behind the gauge and the other to the ground terminal and the needle should jump to "full".

OTOH, you may have already found your problem. The sensor needs to have the S wire connected to the gauge and the "-" wire connected to the boat's ground. Put the spare sensor near the gauge, hook it up with two temporary wires, and play with it.

The only other advice is that the sensors have a 5 hole pattern for their fasteners. Some times the fuel tank is not threaded to accept the fasteners, but you put a horseshoe shaped backing ring inside the big hole in the tank with a long screw, then line everything up and insert 5 short screws. If you have this system do NOT remove all 5 screws until you discover which one is the long screw. If you take all five completely out, the backing ring will fall to the bottom of the tank. Don't ask me how I know this.