boat fuel gauge

[JMac]

With open water season just around the corner, I'll soon turn my attention to getting the boat prepared for spring fishing. I had a problem last year with my Lund Tyee's fuel gauge that I'd like to fix before opener. While on the water, it constantly would read full (even though I knew it wasn't). But once it was trailered, it would give a more realistic reading. Am I correct in assuming that this is a grounding issue???....And if it is, where would I look to try and solve the problem?

[MnWilly]

I don't want to hyjack your post, but I have a very similar problem. 2005 Lund 1750 Fisherman. Fuel gauge will sometimes read completely empty even when there is fuel in it. It will then magically read correctly again. I am assuming mine is also a ground issue. Any suggestions would be greatly appreciated. My problem doesn't appear to be related to being on the trailer or not. Just a random come and go issue.

Thanks

MIKE

[marine_man]

Boat Fuel Gauges are pretty simple instruments.

A couple things to know ahead of time:

1) You'll need access to the back of the fuel gauge

2) You'll need access to the fuel sender. It's either accessed through a small circle cover on the floor, likely in the middle of the floor, midway to rear of the boat or you'll need to remove the center panel of flooring, which will have screws to do this.

3. Here's a wiring diagram:

4. On the back of your fuel gauge there should be wires going to 4 different locations. One will be a black wire, that'll be ground. One will be purple, or at a minimum connect to the "I" terminal, that's the switched power from the ignition. One wire will be blue, or go to a post very near the backlight light bulb. The last wire will be pink (this should always be pink).

Here's how I'd trouble shoot:

1) Turn the key switch on, so the gauge has power.

2) Disconnect the pink wire from the back of the gauge. What does the gauge read now? If it goes from full to empty, and your fuel tank's not full, the pink sender wire is grounded out somewhere between the dash and the fuel tank sender - it may have rubbed though on a sharp edge somewhere - you'll need to try and follow the wire back to the sender.

3) Take a jumper wire (short piece of wire w/stripped ends) and jump between the pink terminal and the ground terminal (black wire). Did you gauge go to full? If so, that verifies that your gauge is working properly. If it didn't you either don't have a good ground connection to the back of the gauge (use a testlight or multimeter to verify) or your gauge needs to be replaced.

4) Get access to the sender. You should see a pink wire (the same one that's connected to the back of your gauge) connected to the center portion of the sender, and a black wire (ground) connected to the outside / screw holding the sensor in the tank.

If troubleshooting on the gauge side of things didn't answer your questions, do this:

5) With the key switch still on, disconnect the sender wire. Did you gauge drop down to empty? If so, things are working properly. If it didn't do anything, as mentioned in 2, the pink wire is shorted to ground and you'll need to trace or replace the pink wire. You can also perform a continuity check on the pink wire between the sender and gauge location.

6) Disconnect the ground wire from the sender and touch it to the pink wire on the sender. Did your fuel gauge go to full? If so, things are functioning properly. If not, the ground to the sender is bad (check with a test light or multimeter), or your pink wire has a complete break in it somewhere.

A couple shortcuts / thoughts here:

1) If you gauge reads full all the time, the pink wire is contacting ground somewhere, or your sender is so sticky it's not allowing the float to drop down when the fuel level goes down. Check the wiring side first.

2) If you gauge read empty all the time there's a break in the pink wire somewhere or the sender's stuck in the down position.

If everything checks out above, it's likely your sender.

marine_man

[boatfixer]

As always, good explaination

[Valv]

EXCELLENT !!!! I vote for posting this in the sticky section.

[JMac]

Wow!!!....Great info.....I'll try those tips on it and see if I can find the problem....

Thanks for the detailed info.....

[MnWilly]

Thanks a bunch Marine Man. It's posts like yours that make this HSOforum a truly special resource.

[fhj115]

I had a very similar situation on my Fish Hawk last year. Gauge would read 1/4 to 1/2 full all the time even though the tank was full. Pulled off back deck to remove sending unit from fuel tank. Moved sending arm up and down and fuel gauge would go from empty to full. Put back in the full fuel tank and still would read 1/2. Found out that the sending unit was good but the float wouldn't "float". Unable to find just a float and ending up replacing the whole sending unit assembly. Works great now. More food for thought.

Brian

[LindellProStaf]

Thank you marine_man. I have a gas gauge problem with a Lund Predator II and wondered how it was set up. This is exactly the info I needed. I am going to get it in the garage and tinker with it now. AND I am looking forward to it now... Thanks again, Barry

[x1957x]

Thanks Marine man.. I am on it like a Northern Pike on a dare devil!! Thanks so much and I will let you know what the out come is...

[bowhunternw]

Wow it is really great that some of you knowledgeable folks on here are willing to share some of this. Got a boat that I am going to sell and the gauge has been goofy from day one. Gonna check this out and see if it fixes it. The trailer wiring thread just fixed me up as well. It was the trailer ground and it was hidden in a little running light on the tongue, major rust and loss of connection.

[BassKnuckles]

Will this be the same process if you have a boat with 1 gauge that has a toggle switch for 2 gas tanks?

[BassKnuckles]

So I shorted the gas gage and it went to full. So I went and bought some wire and re ran 2 lines. I connected each line by themselves and each one would work when I toggled between the 2 on the one gage. When I connected them both up to the back of the gage it acted like there was constant feed to them and when I toggled between them the gage would not move and even stayed when I toggled to the middle which is the off position.

It had a harness before but I thought it would be best to just re run their own lines.

What am I doing wrong?

Then I'm also trying to get my lights working and I disconnected the wires from where the lights plug in to and put a volt meter on it and it read .5 V

The builds look good but.......

[BassKnuckles]

Can someone explain how I would connect another sending unit and have them both run to a rocker switch then from the rocker switch to the fuel gauge?

I am so close!

[BassKnuckles]

So I made this up. Can anyone confirm if this would be the correct way of wiring these?

[marine_man]

That looks correct to me

marine_man