Boat fuel gage problem

[Rockfish]

Boat fuel gauge problem

I have a large under deck 80 gal Al. fuel tank that is long and is low on the keel line down the center of the boat. The tank is 12 inches deep and has a top side installed sender unit for the fuel gauge with two wires on it and a fuel gauge on the dash. The tank is never allowed to get less than 60% full (often much more) and I top it up frequently for the ballast and so there is always a large fuel reserve on the water.

Much of the time , even most of the time, the gauge works great but once in a while it stops working all together. Next time we go out it will usually work again. When it works it is perfect and never jumps around etc. It is as if it just temporarily turns itself off.

This is a system I know little about, so any advice by someone who has previous trouble shooting experience or knowledge with this problem would be appreciated. I have some basic knowledge of marine boat electrical systems but it is limited.

l assume it is either the sender unit, the gauge or a wire/connection/buss/fuse box issue. The gauge is an older electrical/mechanical unit with a dial not a digital read out but don’t know if it would have electronics/chips in it etc but don't think so. My gut tells me the most likely thing would be the sender unit but like I said it is not an area I have a lot of experience in.

 

[wolf]

could be the ground Rick I think thats was a new sender i put in it.. check make sure its not corroded not that hard to figure out ...
an ohm test will help see if the wire is bad

 

[Barnacle Bill]

X2 on the ground

 

[Bait&Sea]

X3, mine did the same untill I cleaned up the connector on top of the tank

 

[leftcoast]

http://www.sportfishingbc.com/forum/showthread.php?28220-Fuel-gauge-reading-in-correct

 

[Gypseas]

Had a problem with my gauge where the needle would touch the back of the screen and get stuck at times. Plug and unplug the signal (S) when it works and watch the needle at close range.
cheers

 

[Rockfish]

Update

Thanks all for the tips.

Today we turned on the gauge with the dash key. The key also starts the main motor. The gauge is working just fine (for now) and shows the tank is full. It occurred to us the needle on the gauge would be a good indicator so one of us did the wiggle test on as many related connections as we could see while the other watched the gauge. Both the connections at the sender which appear to be proper shrink marine connectors did not indicate any change on the gage needle when we wiggled and manipulated them but one of the connections on the back of the gage would cause it to drop a little for a quarter second when it is wiggled. We will take off the nuts on all the fuel gauge connections, clean and reinstall them with a little dielectric grease and run it and see if that solves the problem. If that does not work I guess we cut off and put in two new marine shrink connectors at the sender unit. These connections seem to be shrink sealed and all I think we can do with them is replace them.

It also just occurred to me that it could be related to the key connections. Next time it cuts out, assuming it does, I am going to see if the night time instrument light in it lights up when it is turned on along with the light in the other dash instruments. If the night light in the fuel gauge stops working at the same time as the gauge when I turn on the night light switch, that would tell us something I guess such as the fuel gauge ground may be the problem, especially if the night lights in the other dash instruments keep working.

I don’t really need the fuel gauge but still want it to work all the time, not 85% of the time. I am really good at estimating how much fuel we have burned without the tank fuel gauge and in all the time I have owned this boat the max cost of a top up has only been $160.00. after 3 very long days of fishing and lots of travel on the main so we have never come close to running the tank down on fuel with a tank just short of 80 US gallons. The smart gauge on the dash for the 225 Opti also tells me how many US gals the main has burned but not of course how much the kicker has burned. Lots of fuel in the keel tank gives the boat a little more stability in seas and over the years hearing some guys on the VHF begging for a tow because they ran out of fuel; - let’s just say I never want to be that guy.

PS will have a look Gypseas, but I don’t think the needle is sticking, it just drops down to the bottom when it is not working, - still a good tip.

 

[TGofers]

Sending unit. Mine did that and would kick in and out. Got a new one, universal for 40 bucks. Works great