Adding a secondary fuel gauge to run off house batteries

[Beeb2]

Hi all,

I am considering adding a secondary fuel gauge to my diesel tank that runs off of the house batteries. The reason being that I have two diesel heaters to keep us warm, and I want to keep an eye on the fuel gauge without having to start up the bus occasionally.

However, I have no idea where to begin with this project. How would I go about adding a fuel gauge?

Second idea - is there a simple way to just power my current dash fuel gauge with the house batteries?

 

[cadillackid]

powering that one gauge from an IH dash cluster.. not easily.. you dont have to "start up" the bus... the fuel gauge reads with the engine off and clicking the key on.. or possibly even to accessory... (my DEV bus reads in ACC, my red one does not)

 

[Beeb2]

powering that one gauge from an IH dash cluster.. not easily.. you dont have to "start up" the bus... the fuel gauge reads with the engine off and clicking the key on.. or possibly even to accessory... (my DEV bus reads in ACC, my red one does not)

I've noticed my gauge often doesn't get to an accurate reading until I've driven down the road for 5-10 minutes.

 

[cadillackid]

sending unit is probably starting to go out.. powering it separately isnt going to fix that.


sending units have a physical float so to add a second gauge you'd need to drill a hole in your tank big enough (probably 2-3") for a second sending unit to go in..

 

[Beeb2]

sending unit is probably starting to go out.. powering it separately isnt going to fix that.


sending units have a physical float so to add a second gauge you'd need to drill a hole in your tank big enough (probably 2-3") for a second sending unit to go in..

Yayyy! More problems!!

 

[nikitis]

This is exactly the kind of project I would like to take on for my bus. I love making custom designs like this.

Before I go into it I want to say this:
Mines not that accurate either, but then again, from what I've observed in people's buses, none of them are as accurate as a car. Those tanks are quite large, and the sending unit floats are in the middle of the tanks so the float could be off by 10-20%.

This is common among buses I've witnessed.

That being said the sending unit should be dead accurate if the bus is still and the Diesel is also still. (no sloshing = accurate float).

--------------------

I'm just now thinking about this as you brought up the concept, but how I would likely begin to tackle it is I'd order a 3rd party gas gauge, then Tie into the power and data lines the existing sending unit may have. And literally feed the voltage required into the sending unit from the gauge you bought for monitoring. It may be as simple as that. The voltage and signal may even backfeed into the gauge cluster in the front cab's fuel gauge and turn it on even if off depending how it's wired. Would require a test.

This is obviously just outloud thinking here, and I've confirmed nothing about how they work.

 

[Tejon7]

I wrote a long reply on my phone and lost it. This site kills me sometimes!

Anyway, the short version:

Look up Mopeka Tank Check Pro universal. I have one of their old LPG only versions and made it work on my fuel tank for the very reason you described. The new "universal" model supposedly works with diesel out of the box.

It's an acoustic sensor that measures any liquid tank level. Stick it to the bottom of a tank and you're good you go. It talks to your phone via Bluetooth, or you can set it up to work with Victron GX devices. I'm thousands of miles from my bus but am able to check my tank level any time! (It reads 0% in the image because I was playing with the Mopeka sensor before I left home and forgot to put it back on the tank, but you get the idea)

 

[Beeb2]

I wrote a long reply on my phone and lost it. This site kills me sometimes!

Anyway, the short version:

Look up Mopeka Tank Check Pro universal. I have one of their old LPG only versions and made it work on my fuel tank for the very reason you described. The new "universal" model supposedly works with diesel out of the box.

It's an acoustic sensor that measures any liquid tank level. Stick it to the bottom of a tank and you're good you go. It talks to your phone via Bluetooth, or you can set it up to work with Victron GX devices. I'm thousands of miles from my bus but am able to check my tank level any time! (It reads 0% in the image because I was playing with the Mopeka sensor before I left home and forgot to put it back on the tank, but you get the idea)
View attachment 79612

Interesting! And it's actually accurate? That would be a nice simple solution.

 

[Tejon7]

Seems pretty accurate. I had to mess with mine a lot because it didn't come pre-programmed with the sound speed of diesel fuel, but the new ones supposedly don't need all that extra work.

It's basically just an upside-down echosounder like you'd have on a boat. It sends out a "ping" and most of that energy bounces back off the surface of the liquid in the tank. It measures the time it takes between sending out the ping and the first returning signal. As long as you have an accurate sound velocity for the liquid, your measurement should be right on. I doubt the Mopeka equipment has NASA level timing accuracy, but the results seem pretty good in my experience.

You have to input your tank dimensions for them to work out the %full value, but if I remember correctly that's the largest source of user error.

 

[Beeb2]

Nice. I'll have to check that out.

 

[GreenPastures]

Mopeka makes a tank monitor just for diesel tanks now. I bought 2 one for each fuel tank. Have not installed them yet.