need a smarter switch

[weq92f]

.

In my DD (GMT900,5.3,QC,4x), I've got a 30g tank in the bed equipped with in-tank pump and level sensor. The pump is plumbed through the OEM filler neck and into stock tank.

Inside the cab, I've got a toggle switch and a fuel gauge. Toggle on, the gauge lights up and fuel starts moving. The problem is that when the stock tank becomes full, the current system just keeps on pumping fuel right out the overflow until the aux tank is empty or the toggle switch is flipped off. Twice I've pumped ~10g onto the road while driving having forgotten to flip the toggle switch off.

I'm thinking of adding a time delay switch, like something you'd see in a public bathroom for the fan or the light such that the operator turns a dial to the desired run-time to actuate the device. It will run until the timer dial counts back down to zero. Something fancier like a digital timer-switch would do as well however I'm having trouble finding such a thing, either thing. I've found time delay relay switches but would rather not go there.

Any ideas? How hard would it be to tap into the OEM fuel gauge sensor/feed and have the pump quit once it's full/near full.

I'd really like to be able to use the full capacity of the aux tank without worrying about throwing away money every time I flip that switch!

Thanks,

-klb

[bhap]

How about a "momentary" switch? At least you couldn't forget it was on... or a timed relay?

[Accelo]

How about something like this. Will control up to 12 A.

https://www.amazon.com/Timer-Relay-D...2&sr=8-16&th=1

[Richard]

If doing something like this I would install a float level switch in main tank. Maybe something like this https://www.mcmaster.com/products/li...uels-and-oils/ there are probably others, I just did a quick search.
Main tank switch would be wired normally closed so when it reaches the full fill point it would open and shut off pump. A similar switch could be wired in series for the Aux tank. But in reverse, normally open. It would shut off pump when there is no fuel in the tank. Would create a fully automated system that transfers fuel from one tank to the other. If amperage draw of pump is to much for the switch's just install a relay.
Edit- Failed to see price on the link I provided is ridiculous. Here is another switch that is more affordable and will accomplish the need https://www.ebay.com/itm/22505267518...Bk9SR8ry8tyHYw

[kwmech]

For safety I'd plumb in a switching valve and keep them separate. See some of Hatzies threads regarding plumbing and wiring for an aux tank. Having gasoline with theoretically an open hose in the filler is just asking for trouble, whether its being pumped or not

[weq92f]

.

Thanks for the replies gents. I like the eBay digi timer switch and may attempt to download the manual for it to make sure it would do what I want and that I'd know how to wire it up. The ad for it doesn't mention a trigger so I'd have to read the manual there.

I know this setup isn't optimum but I believe I can make it work and be safe with it. What I've been doing is filling it with only enough to fill the stock tank. This way I don't have the possibility of throwing away fuel or making things unsafe.

-Kevin

[hatzie]

I have a tank in the bed that I usually fill with red diesel for the tractor, skid steer, and big loader but can fill it with gasoline for a long trip. The tank has a 12v pump and auto shutoff dispenser handle that's pretty close to a high volume fuel pump at a gas station.

I pull over and fill the tank from the AUX tank in the bed and fill both tanks back up at the next Loves or TA or Pilot or Flying J or ... that are really close to the exit ramp. It gives me a chance to stretch my legs at even intervals so I don't nod off.

I've read about GM dual tank systems that use the PCM to handle fuel pumps and level senders in the tanks.
Your other option is to use the 1981-1991 motorized valve system that switches the supply and return from tank to tank. I can't guarantee the EVAP monitor in the PCM will not get unhappy about it if you don't add a fuel tank pressure sensor and EVAP vent line to the tank.

[weq92f]

Originally Posted by hatzie

...<snip>... I can't guarantee the EVAP monitor in the PCM will not get unhappy about it if you don't add a fuel tank pressure sensor and EVAP vent line to the tank.

Occasionally, I get a CEL after filling from aux to main which turns out to be "gas cap" related.

-klb