Unknown fuel level

[scot71]

This is a problem that I have dealt with for a few years now and haven't been able to come up with any ideas for a reason. Thought I would throw it out to all if you fine folks and see what ideas you all might have.
When I bought my boat from the previous owner, the fuel gage didn't work. The first thing I did was replace the sending unit with a WEMA sss/ssl float style unit. This did not solve the problem. Next, I changed out the gage itself, with a Moeller brand. Still doesn't work correctly.
Here's the weird part. When I fill the tank and use the boat. The gage will drop to about 3/4 of a tank and not drop any farther. But, if I unbolt the sending unit and raise and lower it in the tank. The gage moves just like it should. This is a problem that kind of has me stumped. There is nothing even near the float to keep it from moving when bolted in.
Needless to say. This really has me stumped. Any and all thoughts, ideas, and suggestions would be greatly appreciated.

 

[Beachbummer]

So, maybe this is not it, but used to be a problem on SeaDoo floats... Any chance the float is "Gas Lodged" and gas does not make it float? It just sits there? Any chance the float does not move freely? (biding/dirty stuck?)

If you pull the float out and can move it by hand and the gauge reflects your movements either something electrical changes when you put it back (Wires cracked? touching?) Or the float doesn't really "float"?

Just brainstorming here....

 

[scot71]

The float does "float". When I would unbolt it. I would just run it up and down in the gas in the tank and it would read just fine. It only stops working once it's bolted down.

 

[Beachbummer]

That is strange. Can you identify the moment? Is it when it's tightened? I know the tank is plastic, but any chance something about bolting it changes the electric path, like something goes to ground? I suspect if you go down there with a multimeter you can figure it out, specially if it changes in front of your eyes as you bolt it on. maybe the holes are not aligned and bolting it down deforms the case and makes something touch?

Something's going on for sure.

 

[treeskier]

Is it possible when you tighten it down that the tightening causes the slide the float rides on to bind in any way ? Is is possibly touching the the bottom of the tank and pinching the unit in some way? IDK beyond those possibilities i wouldn't have a clue.

 

[Julian]

Many of us ran into fuel sender issues with the older boats. Turns out the older senders couldn't handle the resistance change with ethanol. There is a newer model sender that you can install that fixes this issue. Documented below (also linked in the FAQ):
https://jetboaters.net/threads/my-ongoing-fuel-sender-saga-good-news-replacing-fuel-sender.4320/

That doesn't explain your float issue though as you've replace both the guage and the sender for whole new models.....

My only guess is there is a wire connection issue at the sender. When you pull out the sender it is putting different pressure on the wires and making a complete connection vs when its installed????

 

[Jgorm]

Are you sure your going below 3/4 tank? I thought there same thing was happening but ever time i physically checked the tank it was still pretty full and just using less gas then i expected.

 

[scot71]

Are you sure your going below 3/4 tank? I thought there same thing was happening but ever time i physically checked the tank it was still pretty full and just using less gas then i expected.

Yeah, positive on that one. There have been a few times that I've ran it well below half a tank, but it never goes below 3/4 on the gage.