Grounding a fuel tank??

sutor623

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I have an aluminum fuel tank in my 20' boat. It is 64 gallons. I removed the tank after it had been setting for 7 years. I was going to clean it out really good and get any varnish/debris out, but luckily the previous owner had used E-free gas with stabilizer. Believe it or not, the tank was very clean inside.

Anyways, before I took the tank out, the fuel gauge worked. Now, it doesn't. When I turn the key on the gauge goes to 1/4 tank, then when I turn it off it will go back to 0.

I am pretty sure that something changed when I re-installed the tank. I pulled the sender out so that I could see inside the tank, and then re-installed it.

There is a sender wire and a ground coming off of the fuel tank that also runs to the fuel gauge. But as I recall, those were the only two wires that went to the tank. Shouldn't there be a wire from tank to ground to ground the tank out???? I didn't see any other wires. Here are the two wires that I speak of (figure 4):



There is an angled piece of aluminum on the top of the tank that I could easily fasten a wire to and run it under the floor and ground to my motor. Should I do it? (Bottom of bottom picture.)

 

alldodge

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The tab is used by many boat manufactures as the main ground. My Formula has a 12AWG light Green wire which connects to the boats ground buss bar. As yours shows, the ground is either connected by a terminal or some connect under one of the bolts holding the sender.

Remove the black wire, turn key to ON (don't start) and touch the black wire to the pink wire/terminal. Your gauge should peg full. If it does your sender has been damaged. If the gauge doesn't peg then check the ground and also check for 12V on the pink wire and at the gauge.
 

sutor623

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The tab is used by many boat manufactures as the main ground. My Formula has a 12AWG light Green wire which connects to the boats ground buss bar. As yours shows, the ground is either connected by a terminal or some connect under one of the bolts holding the sender.

Remove the black wire, turn key to ON (don't start) and touch the black wire to the pink wire/terminal. Your gauge should peg full. If it does your sender has been damaged. If the gauge doesn't peg then check the ground and also check for 12V on the pink wire and at the gauge.


Ok, thank you. So there should be 12v on the pink wire? And the black wire is connected to the tab on the sender, like you said. But that wire should be continuous with ground?
 

alldodge

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Ok, thank you. So there should be 12v on the pink wire? And the black wire is connected to the tab on the sender, like you said. But that wire should be continuous with ground?

In most cases the pink wire can have less then 12V, all depends on how much resistance the sender has at the time (level of fuel in tank). The black should be a continuous ground. What you want to find out is if the gauge will peg full if you either pull the black wire off and touch it to the pink wire, or jumper from pink to black.

If it doesn't peg the gauge, then there is either an issue with the wiring of the ground. Just trying to rule out the sender first.
 

sutor623

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Ok,

So, I touched the black and red wires, and the gauge pegged out at F. I disconnected the black wire, and gauge went to E. I checked the black wire with continuity to engine ground, and it is continuous. For some reason the gauge was working when I turned the key on. Bad connection maybe?

Now that I know the gauge is working, and I THINK the sender is working, here is another question. When my tank is full, I am only reading 7/8 of a tank. I guess the float isnt coming all the way up due to physics? And, when I turn the key off, the needle on the gauge stays about in the same spot as it was in with the key on. Is that normal or should it do to E since there is no more voltage going into the red wire? Thanks again!
 

alldodge

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Sounds like your gauge may just be dragging. Mine was doing it, so I would tap on the gauge and it would go the rest of the way down, or up when ignition was on. I wound up just replacing the gauge.
 

sutor623

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Sounds like your gauge may just be dragging. Mine was doing it, so I would tap on the gauge and it would go the rest of the way down, or up when ignition was on. I wound up just replacing the gauge.


Cool thanks for the help. My main issue is that this tank holds 64 gallons of fuel, and I use 10 gallons an outing, 1-2x per month. So, basically, I only use 10-20 gallons a month, and top her off after a trip. I use Ethanol free fuel only, but I dont want the fuel in the tank to go bad. I do not want to have to buy a smaller fuel tank ($3-400 or more) but would like to be confident knowing that I have a SOLID 1/2 tank before a fishing trip. It is also a nuisance carrying around 500 lbs. of fuel everywhere I go when I am only going to use 10 gallons!!!

Maybe I should consider a new gauge and a reed style fuel sender because they are more accurate?
 

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alldodge

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If you can tap on the gauge and it moves then yes replace the gauge, as for if the read/tube type senders are more accurate, IMO the jury is still out. Gauges are approximations, only way to know how accurate is to top off the tank at various levels to see how close they are. Like the gauge in your car, it probably stays full for a while until it starts to drop (least mine do).

Agree I never fill my tank up, just to much weight to haul around causing to burn more fuel
 

sutor623

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If you can tap on the gauge and it moves then yes replace the gauge, as for if the read/tube type senders are more accurate, IMO the jury is still out. Gauges are approximations, only way to know how accurate is to top off the tank at various levels to see how close they are. Like the gauge in your car, it probably stays full for a while until it starts to drop (least mine do).

Agree I never fill my tank up, just to much weight to haul around causing to burn more fuel


Thanks. I have considered adding a fuel management system to the engine. My Lowrance allows me to tap into my fuel line and will tell me how much fuel I am burning, have burned, and where the "sweet spot" is in certain conditions by comparing fuel usage to GPS speed. Sounds like a winner there huh?

Here she is:
http://www.lowrance.com/en-US/Products/NMEA-2000/fuel-flow-sensor-en-us.aspx
 
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alldodge

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Not bad, had several friends which added similar items and they liked them
 

sutor623

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Cool, thanks for all your help. I am going to clean up all my connections, put some corrosion protection on them and see how the gauge works. I may also put on an hour meter so that I can figure out how many GPH I am burning so I will have an idea on how much fuel is in that tank.

Would rather just have a 30 gallon tank and keep it topped off..............
 

sutor623

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Sooooooo,

Cut the key on yesterday and guess what? Initial problem came back. When I turn the key on, the guage goes back down to E. I pulled the ground off the tank and connected it to the red wire, and the gauge pegged at F, then when disconnected, back to E. When I reconnected the wiring, the gauge still stayed on E with the key on.

Sounds to me like my fuel sender is the issue right? This is good because at least I have a good excuse to go ahead and buy a reed sender now ($70!!)
 

alldodge

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Agree, sounds like you have the issue found, intermittent connection inside the sender
 
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