Hot Rods 2 Gas Gauges on one sender?

In order to eliminate the gas filler on my 'glass '31 chopped sedan delivery, I'm considering a 2 gallon Moon tank in front of the grill shell with a high volume fuel pump to transfer the gas from the Moon tank to a hidden tank behind the seats in the cargo area. Obviously I need to know when it is full or close to it. I'll also have a hidden switch to turn the transfer pump on and off. Like a VW or motorcycle, the Moon tank will serve as an emergency reserve! Thanks in advance for your thoughts.

 

Sound like your idea works better than my broken gas gage on my 56 buick wagon. When it stops running I have to push it to a gas station. MAN THAT CAR IS HEAVY! Bruce.

 

if you keep the moon tank full and your hidden tank holds more than 2 gallons no need for 2 gauges.your hidden one if gauged will show the 2 gallons from moon tank when pumped in.for moon tank find a wooden ruler mark when moon tank full just like original bug had.

 

If you know what the capacity of the hidden tank is and you know what the amount of gas the gauge
shows you have left simple math would tell you how much to add in to fill, ie if the tank holds 12 gal
and you show 1/4 full you should need about 9 gallon to fill it. If you allow a cushion for the
errors gas gauges seem to always have add only 7.5 to 8 gallons plus your 2 gallon tank if it was
used. As you drive the car and track it's fuel economy you will be able to pretty accurately figure
exactly how much to add.

 

Vent the hidden tank to the moon, where you can see (section of clear line, maybe?) or hear when there is gas flowing through the vent line. When that happens, the hidden tank is full. Then all you need to do is top off the Moon.

 

If the hidden tank is higher than the Moon, you WILL have problems filling it, as well as problems with it emptying onto the ground.

Cosmo

 

Seems like a lot of bugs in this plan.

If your filling from the front and transferring threw a fuel line pump you going to have to fill the moon tank, stop, transfer it all the add another two and so forth. Seems like it'd be a song and dance and quite a bit more time just to get a tank of gas in it.

Also comsider Gravity and the issues your going to run into filling the hidden tank from the bottom... Unless your running even more line and going in threw the top I guess.

And finaly the venting of the hidden tank. There's no way that thing isnt going to get overfilled at some point.

I suppose a fat vent line out of the car were you could see it spraying out gas as you stand in front of the car could work other wise your either going to end up with a very pressurized tank and/ or a transfer pump that's trying to stuff more fuel into a full tank when your math doesn't agree with however the station pump is calibrated.

I think there is probably a way to make your remote set up work I just think it needs some more thinking on it.

 

I can imagine the head scratching going on when you pull up to a pump to fill a 2 gallon moon tank and it takes 15 gallons. I think in principle your idea could work if the hose pumping into the larger tank goes into the top and only just inside the top. If it goes deeper into the tank there would be a chance of it syphoning back to your moon tank I believe. For a way of knowing how much is in the main tank, have you looked into an oil level sensor or windshield washer level sensor from a newer vehicle? Maybe something like one of these could be used with a simple light that comes on when the tank is full?

 

My brother has roped me in on this and I think we can make it work. My idea is to have a float switch in the small tank that will turn on the pump and then a float switch in the main tank to turn off the pump. We will have a fill neck in the main tank in case there is a pump failure. I think it will be fun to put 12 gallons of gas into a two gallon tank at the gas station.

 

You will also need to have a one way check valve in the line from the Moon to the main so that gravity does not force the gas back into the moon, and all over you shoes. Don't expect the pump to work in that capacity, cuz I don't think that's gonna happen. as soon as you turn it off, the gas she comes rushing back. It's also going to take a while to fill, unless you put about a 1" transfer hose!

 

Good luck with this, there are numerous pitfalls awaiting you on this project.

 

Also a possiblity of sparks from an auxiliary pump while filling, yeah I know remote, but the gas stations may not like the idea.

 

It does sound kind of like "a brain fart" to me, sorry, not trying to be rude, just calling it as I see it.

 

Sounded pretty silly when I first heard about it. But then it became kind of intriguing. A good puzzle. Already figured in a check valve. Transfer flow isn't a problem. Gas at the gas station isn't very fast.

Anybody can put gas in a tank the easy way. This sounds more interesting. I did mention that a filler will be avaliable on the tank if this all goes sideways.

 

I'm on the "more trouble than it's worth" side of this fence, but in answer to your original question, you can run one gas gauge off of two senders if you just have a toggle switch. My 1985 Chevy pick up has two gas tanks, each gas tank has a sender but there's only one gas gauge. There's a switch on the dash will you switch from left to right tank. This all sounds complicated, but is actually quite simple and straightforward.

 

Question was "two gauges on one sender ".

 

if you use a double pole / double throw switch the second gage would work when your transfer pump does.

 

I have never tried this, but I think you can run 2 gauges off 1 sender with seperate wiring run to each gauge from the sender with no need to have them running thru a switch.

 

It is something that YOU need to fully think through and fully diagram the wiring and plumbing plans; but it should be doable and safe if properly done.
A double throw double pole switch should take care of the sender to two different fuel guages and the transfer pump. A relay will likely be needed for the transfer pump. The tank may need a high level shutoff for the transfer pump, and of course, you will need a check valve in the transfer line. Tank venting is needed and is a bit of a challenge to safely locate and keep hidden. ...but think it through and it should be a neat feature.

 

Russ, I have this pretty much thought through. I will place the vent in the left taillight bracket. I was trying to avoid a switch for the gauges but I think I am not going to use the second gauge after all. I plan to install a float switch in the main tank to unlatch the relay and shut off the pump. I will also have a switch for the transfer pump in case something goes wrong.

 

This probably goes without saying, but I'm saying it anyway. Chose the float switches that you're going to put in the tanks very carefully. I assume you're talking about a sealed reed switch with a magnetic trigger on the float.

 

To simplify this, go with a 'high level shut off' switch in the main tank and a manual switch to turn the transfer pump on. A indicator light or two to show when the transfer pump is running would also be an excellent idea. You'll need a one-way valve between the moon and main tank. I'm assuming that the main tank will be the connection point for the engine and that the moon tank will only be the fill point. To fully automate this, you'd need a 'low level shut off' for the pump in the moon tank but I suspect that fuel slosh while driving would probably cause the pump to cycle needlessly and possibly run the pump 'dry' (no fuel), shortening the pump life.

You could forgo a gauge, using the moon as your 'reserve'; when the main tank is empty, pump the two gallons in the moon into the main tank and start looking for a gas station....

 

The basic and simple setup is a float switch in the moon tank to a latching relay that will turn on the transfer pump, a check valve, then a float switch in the main tank that will unlatch the relay and shut off the pump. A switch to shut off the pump in case there is a problem or for service. The main tank will have a fill neck on top that can be used in the event that the transfer pump fails. I plan on installing a vent in the bracket for the left taillight.

I am starting to look for the float switches. They will need to be sealed for safety reasons. If anybody knows of a source for the switches let me know.

 

The problem with this design is it isn't 'fail-safe'; in other words, automatic pump shut-off may not be guaranteed. If the main tank isn't filled completely or if either float switch malfunctions the pump may keep running even if no fuel is available at the moon tank. Might also be a problem if you have to fill the tank with a 5-gallon can on the side of the road. A 'low level shut-off' at the moon tank will fix this, although I'd still install a manual override switch and an indicator light to show when the pump is running. Ideally, you should have both a high and low level switch in each tank, with needing both the high level in the moon tank and the low level in the main tank calling for pump operation, while either the low level in the moon or high level in the main causing pump shut-off. This is pretty much standard pump circuitry when there's more than one tank involved. And rather than a latching relay, I'd use a 'holding coil' type circuit (which is electrically 'latched' rather than mechanically).

 

http://www.cynergy3.com/blog/how-select-correct-float-switch

 

Steve, thanks for the comments. I am working them into my design.
Ebbssped, thanks for the link. Very helpful.

This is still evolving but I think it will work. Thanks for all the comments and of course I will update as we move along.

 

Couple things to consider is the pump & details.

• Fuel pumps are rated in GPH. (Gallons per Hour) For example a 50 gph pump will comfortably feed an engine but it will take 12 minutes to transfer 10 gallons. That is using a 3/8" fuel line so faster may need a greater pump & possibly lines.
  
• The suggestion for an inline check valve is correct unless the pump has an internal check, venting back to the moon tank will give you an indication that the other tank is full. The vent has to be a decent size so as not to pressurize the main fuel tank.
  
• If there is an emergency fuel cap on the main tank then it will have to be sealed so that it does not leak all over when it is filled to capacity to flow fuel back through the vent to the Moon tank.
  
• The pump will be running the car battery down while the car is being fueled. Venting gas as an option on to the pavement with the electrics running?
  
• Visually if the Moon tank is full it is full.
  
• It may be safest to install a concealed fuel door to fill the main tank & fill the moon tank separate of one another. When the main tank indicates a 1/4 then transfer & look for a gas station. The less complicated the safer & more reliable the vehicle. Either way you are installing a filler into the main tank so it may as well be external where it is safer versus risking a fuel spill inside the ride. Gas stinks and the last thing is it sharing the cabin.

The hazard with the reserve tank on the old VW was switching to reserve and not filling up soon enough as they had no gauge except for the dipstick. When the engine chugged then it was switched over to reserve. If a person forgot to return the tank to the reserve when he filled up then he was screwed when it stumbled. The advantage here is the fuel gauge so there will be lots of warning provided the reserve tank is full.

My 60 VW bug had a screaming 36hp which was good for the prairies where I was going to school but a real sweat on the steep hills going home for the occasional visit.

 

Question was written wrong - poster doesn't want two gauges, he wants two tanks which means two senders. Just sayin.

 

No, I want a single sender in the main and two gauges; one on the dash and another near the Moon tank

 

You can run both gauges with a switch between them, only one will register at a time.

Tanks wise you have to be able to isolate the tanks or keep the tops of them equal or you will have problems with fuel transfer. I have used a second tank for a reserve tank, with a splitter like a dual tank truck has. When one tank runs out switch it and head for the gas station. That part of the idea works like a champ.