Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

[rmurray]

I want to figure out my fuel system. I have two gas tanks on each side. At the helm, there is a 3-position toggle switch. Up is "Port" and down is "Starboard", and the center is either "Off" or "Both", I'm not sure. I have one fuel gauge. It will register when the switch is set to "Port", but then it doesn't register for the other two settings. At the back, the fuel hoses from the tanks go into a small unit at the transom (regulator?, fuel pump?, water separator?, I'll have to inspect it more closely), and one hose comes out and goes to the motor. Both tanks and the small unit have two wires coming off them (probably +12v and ground). The 3-position toggle switch has six connectors at the back. I want to check and possibly rewire the whole system to make sure it works correctly. I would prefer to be able to draw fuel only from the selected tank on the toggle and have this specific tank's level show in the gauge. Can anyone help with setting this up, or providing a wiring diagram/schematic? I'm an experienced Do-it-yourselfer with limited boat experience. Thanks!

 

[dingbat]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

I've got 2 tanks. The main tank is 92 gallons and the reverse is 52. Both tanks have senders and they are wired basically as you describe with "off "being my center position.

Both of my tanks are plumbed to a manual selected valve and then run thru the filter /separator and then out to the motor. The only thing I can think of for your third small unit might possibly be filter/separator with a water alarm.

I have no idea how you would incorporate something into the tank selection valve that would give you feedback as to which position the valve is in unless you want to spend quite a few bucks in the process.

It's easier just to remember which one of two tanks I'm riunning on at the time.

 

[Chris1956]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

My friend's 30 footer had the dual motors, dual fuel tanks (stbd, port) and a single fuel gauge on a two position switch. He could switch the gauge between the two tanks. It sounds like your set up. If so, you want to use both tanks at the same time, so you do not get a list as one tank gets empty. Since the two motors should use about the same amount of fuel, toggling the gauge between the tanks is not necessary, until you start to run low. You should fix the sender or wiring on the non-working tank. I do not think the center position is for both senders, since an average fuel level is not important.

You need to see if your two tanks are independent of each other. The hose should run to an independent water seperator, and then to the motor. If not, I would suspect someone has modified the set up.

 

[QC]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

Although I agree with Chris, most boats are not setup that way. I have had two boats with twin "saddle" tanks (one on each side). Both had/have a single gauge and a switch to show level in the individual tanks. No "common" for both though. Again I agree with Chris, not helpful, necessary or desirable.

First one had a single tee where both lines came in and then a single line went to the water separator and then the engine. There was no way to isolate the two tanks to draw from one at at time other than I guess a vice grip on one of the lines . I installed the tee and made sure both lines were the same length and she drew fuel down equally, it was wonderful, I loved it.

On my current boat however, I have the same tank setup and gauge setup, but it came with an either/or manual valve. It would only draw down from one tank at a time as the valve had no "both" setting. Again, single gauge, port or starboard switch for the gauge, no common. Because of my previous experience with a boat that would draw fuel evenly from both tanks I pursued the same with this one despite warnings here that it would not work . . . Anyway, I bought a rather expensive, but also manual, valve that allows port, starboard or both.

The ability to isolate a single tank is indeed important if you run one dry or get contamination in one etc. But like Chris mentioned that ability to draw evenly from both keeps from any listing issues which I hate. I made up equal length lines (checked at least 10 times . . . ) new fittings, new attachment points, all the way to the tanks and from the valve to the engine. This one will not draw evenly After discussing here, I believe the difference is that I have anti-syphon valves in each tank with this boat and to make it work right they probably need to be removed although that is not a good idea . . . There needs to be exactly the same "pull" required from both tanks for them to draw off equally. Apparently my previous boat did not have any anti-syphon valves.

The point of this rather long explanation is that although it is a pain in the arse, a valve that allows you to draw independently is best, if you get lucky and it will draw equally and the valve has a "both" setting, then great. And I am serious about the vice grips if you only have a simple tee . . . Imagine if you were to run one tank dry and the other had one precious gallon left . . . what do you think will be going to the engine?

As far as the gauge switch is concerned, I simply tried different terminals with the wires until it worked right . . . Also, I have heard that electric fuel tank valves are very finicky and failure prone. Good luck.

 

[rmurray]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

Ok, so I see how the listing of the boat could be a problem. I guess I assumed that switching to "Port" meant that only the port tank was being used. After reading the posts, it appears that both tanks are probably being used, the switch just allows me to check the levels in each tank because I only have one gauge. Is that right? It probably is a water separator at the back and it is pretty close to being exactly in the middle of both tanks. I thought it might be some kind of electric valve that was controlling the fuel flow from each tank, but now I doubt it. I still have to inspect it. At this point, I'll just try and get the sender in the starboard tank to register on the gauge. Hopefully I can figure out the toggle switch and all the wires that attach to it. Thanks for the info!!!

 

[QC]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

the switch just allows me to check the levels in each tank because I only have one gauge. Is that right?

Yes. Probably so.

I thought it might be some kind of electric valve that was controlling the fuel flow from each tank, but now I doubt it. I still have to inspect it.

My guess is that if you had an electric valve it would be a sepearte switch fron the gauge . . .

At this point, I'll just try and get the sender in the starboard tank to register on the gauge.

That'll be OK if they are pulling simultaneoulsy and 100% equally, if not, this may be a bad plan. Do you know what your average MPG is? Total fuel capacity? If so, I would have a conservative max range in my head to work from and use the gauge as back-up so to speak . . .

 

[rmurray]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

25 gallons a side (50 total). Probably 2 mpg I'm gessing. I figure that out soon. Thanks again QC. I'm off to Mead Thurs morning! I'll skip a rock for ya...

 

[rebars1]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

Mine is set up like yours with two tanks, one guage. There is a solinoid valve for each tank just before the "T". Normally closed, the each valve opens when the switched is flipped to that side (tank). I start with both tanks filled, run one to half empty, then switch to the other until it is empty, then switch back to the first tank. You should be able to hear the solinoids click when you switch it back and forth.

It helps to position the toggle lever so that it points to the tank it opens when you flip it, instead of up and down.

Not sure of the wiring diagram, sorry. Maybe I can photo the back side of my panel.

 

[rebars1]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

I had a similar problem when I resurrected my boat (no reading from one side). After hearing the "click at each solinoid, I then checked that I was getting 12 volts to the senders on each tank as the lever was flipped. I finally had to pull the sender out of the tank and work the lever (had not been used for about ten years), then all was good.

 

[Silvertip]

Re: Fuel Toggle Switch, Dual Tanks, One Gauge...Help!

Here is a schematic for a dual temperature sender configuration. Just substitue the temp sensors for your fuel level sender in each fuel tank. Three terminals are used on the switch and there is no center off (although there could be). The second set of three terminals on your switch might just be to control an electrical fuel selector setup. You need to figure that out and get back to us. For all we know someone might have added two electric fuel pumps which is another bad idea if there is no dead engine shut off protection.