LRA aux tank fill-up observations

[prharper]

I have had my LRA 24.5 for about two years now. I typically fill both tanks at Costco.

After driving around for days/weeks, I refill the main OEM tank from the aux until the red light comes on the LRA gauge and LRA (upgraded) pump stops.

On the next Costco fuel up on the LRA, station pump typically cuts off on avg. 20.5 gallons.

Do I have ~ 4 gallons in the aux tank just hanging out?

Curious on your experience.

 

[NTV]

I have had my LRA 24.5 for about two years now. I typically fill both tanks at Costco.

After driving around for days/weeks, I refill the main OEM tank from the aux until the red light comes on the LRA gauge and LRA (upgraded) pump stops.

On the next Costco fuel up on the LRA, station pump typically cuts off on avg. 20.5 gallons.

Do I have ~ 4 gallons in the aux tank just hanging out?

Curious on your experience.

I have the exact same experience. Takes about 30min to transfer to go from full Aux to red light. I think you can keep running the pump on red to draw that last 3 ish gallons but for me I am going to save that for situations where I must have those last few gallons. There is an auto shut off feature after the pump goes dry and my guess is you will hear the pump at that point, but I haven’t tested this yet on my rig.

 

[radman]

I have had my LRA 24.5 for about two years now. I typically fill both tanks at Costco.

After driving around for days/weeks, I refill the main OEM tank from the aux until the red light comes on the LRA gauge and LRA (upgraded) pump stops.

On the next Costco fuel up on the LRA, station pump typically cuts off on avg. 20.5 gallons.

Do I have ~ 4 gallons in the aux tank just hanging out?

Curious on your experience.

samsies for me on all of it. Costco, ~19-20 gallons max in the aux tank.

 

[CharlieS]

For any of you with the original pump, do you notice a dramatic increase in sound coming from the pump when it is in the final minute or more of the fill?

I only have the 12.5 gallon, and the pump gets a lot louder when it gets to pumping air. FWIW, I have at times filled it to 12gallons or so.

I wonder if the design of the 24 gallon tank leaves a few gallons below the exit point to the pump. You could open the drain plug into a clean container when it is "empty" to measure how much fuel remains.

 

[Fisher23]

I have had my LRA 24.5 for about two years now. I typically fill both tanks at Costco.

After driving around for days/weeks, I refill the main OEM tank from the aux until the red light comes on the LRA gauge and LRA (upgraded) pump stops.

On the next Costco fuel up on the LRA, station pump typically cuts off on avg. 20.5 gallons.

Do I have ~ 4 gallons in the aux tank just hanging out?

Curious on your experience.

That is Normal .. Push the button again to get the remainder transferred.

If you have the original fuel transfer pump you can hear a difference in noise level when it empties the aux tank, it gets noticeably louder.

 

[kcjaz]

My 24 gal is just recently installed and I've only transferred fuel twice so far. The last time I let it run until the auto shutoff beeped and shut the pump off. I didn't try turning on the pump a second time to get any more transferred. When I filled the aux tank it took 22 gal. Next time I think I'll try running the pump again after auto shutoff and then drain /measure what's let through the drain just to what's really left.

 

[Artie]

40 gallon with upgraded pump.

I can’t get the last 2-5 gallons out of mine either, I’ll pump until pump shuts itself off. @Fisher23 just so I understand, to get the remaining few gallons out I should turn the pump back on after it shuts itself off? If this is the case then why does it shut itself off in the first place?

 

[eatSleepWoof]

If this is the case then why does it shut itself off in the first place?

I don't have an aux tank so I can only theorize, but I've heard many times from different sources that running the fuel tank to very low levels is hard on/bad for your vehicle's fuel pump. It may be a similar story with the pump in these LRA tanks, so there's a cut-off at a level just above the point at which the pump will start to struggle (and perhaps excessively wear itself out), with an option to override that and get the remaining fuel should that really be necessary. Again, just a theory.

 

[radman]

I don't have an aux tank so I can only theorize, but I've heard many times from different sources that running the fuel tank to very low levels is hard on/bad for your vehicle's fuel pump. It may be a similar story with the pump in these LRA tanks, so there's a cut-off at a level just above the point at which the pump will start to struggle (and perhaps excessively wear itself out), with an option to override that and get the remaining fuel should that really be necessary. Again, just a theory.

plausible, however, these pumps are plumbed outside of the tanks, with a hose connected to a "low point" of the tank. Either that low point isnt low enough, or the shape of the tank doesn't allow it to fill all the way, or maybe something to do with air gap?

 

[Pierce]

I have a 24 gallon tank on my 80 and a 12.5 on my 200. The 12.5 is new and does a full 12 gallon transfer.

The LRA switch failed on the 80. The new instructions warn against a tight fit when fitting the switch. I didn’t see that warning when installing it in the 80 (5ish years ago??). Unbeknownst to me I had cracked the LRA switch’s housing. The switch would originally only transfer 20 gallons and by the time i swapped in a factory on off switch it’d just turn off after a minute or two.

I don’t regret switching to a factory style dumb switch. I’ll do the same thing to the 200 when my wife gets done with it. You can hear the change in pitch when the pump goes dry.

This may go without saying but with a regular on off switch and upgraded pump I’m able to transfer 22ish gallons in the 80. Same setup as the 200.

 

[TeCKis300]

For any of you with the original pump, do you notice a dramatic increase in sound coming from the pump when it is in the final minute or more of the fill?

I only have the 12.5 gallon, and the pump gets a lot louder when it gets to pumping air. FWIW, I have at times filled it to 12gallons or so.

I wonder if the design of the 24 gallon tank leaves a few gallons below the exit point to the pump. You could open the drain plug into a clean container when it is "empty" to measure how much fuel remains.

Yes. The pump is very loud when run dry. It's the nature of these types of fuel pumps and I suspect it's not intended to ever be run dry as it sounds like a coil or diaphragm bottoming out.

Here's a video someone else posted

Cruiser Brothers 12.5 LRA Aux Tank Install in LX570

Tank filled. So weird being able to fill over 26 gallons! The dual filler neck is pretty awesome. Skew the nozzle towards the tank you want to fill. Then re-position and fill the other tank. Filling the main tank does seem a tad more sensitive, at least at the Costco pumps I always use. It...

forum.ih8mud.com

 

[Artie]

I don't have an aux tank so I can only theorize, but I've heard many times from different sources that running the fuel tank to very low levels is hard on/bad for your vehicle's fuel pump. It may be a similar story with the pump in these LRA tanks, so there's a cut-off at a level just above the point at which the pump will start to struggle (and perhaps excessively wear itself out), with an option to override that and get the remaining fuel should that really be necessary. Again, just a theory.

That makes sense. I don’t plan on getting every last drop out but it would be nice to know where those extra gallons are at and if they are accessible if need be.

A few gallons out of 64 don’t sound like much but those 25-45 miles could make a difference in an emergency. Also, I don’t make a habit of running either tank completely empty, I don’t think I’ve ever seen my low gas light come on for the main tank.

 

[CharlieS]

In an absolute pinch if you needed those last bits of fuel, you could drain from the drain port and pour into the main tank.

 

[kcjaz]

There are several installation and tank variables here so we all won’t get the same experience. This thread is good though to help us all understand what others report so we can decide if we want to mod or change something.

The reason the LRA kit comes with an auto shutoff is simply to protect the pump from running dry if you forget to shut it off. If it were to run dry for more than a few minutes, it will eventually die.

All the auto shutoff knows is what the level switch in the aux tank tells it and that isn’t super precise. You will likely get different results while driving vs parked. They also built some conservatism in the shut off set point. My LRA instructions say if you start the pump with the low level red light on, it will run for two minutes. So you can do this to get the last few gallons out. You may be able to hear the pump and if so, the soulnd will change and you can then shut it off. I have the Atex upgraded pump and I can’t hear it running in the cab while moving (my chewed up AT tires are now annoyingly loud).

If you run the pump until it sucks air and you still have more than one or two gallons, I’d say your pickup tube isn’t properly installed.

 

[UPR LC]

I don't have an aux tank so I can only theorize, but I've heard many times from different sources that running the fuel tank to very low levels is hard on/bad for your vehicle's fuel pump. It may be a similar story with the pump in these LRA tanks, so there's a cut-off at a level just above the point at which the pump will start to struggle (and perhaps excessively wear itself out), with an option to override that and get the remaining fuel should that really be necessary. Again, just a theory.

Vehicle fuel pumps are in-tank and the fuel actually helps keep the pump cool. Running below a 1/4 tank reduces the cooling effect for the pump. There is also more potential to suck in contaminants that are in the tank at low fuel levels (higher concentration of particles).

To help the LRA auxiliary pump, it is best to mount the pump as low as possible (below tank if possible) and provide a baffle for the in-tank pickup fitting/hose. You want to limit the amount of air that can get sucked into the pump at low fuel level. One other option if parked, make sure the pump intake location is the low point of the tank so the fuel flows to the pickup location.

 

[nuclearbeef]

I have backed the left rear wheel up onto a curb (fuel pickup is front right) then run the pump with the gas cap off so I could see the fuel transferring.
Ran until the pump was pumping air.
Filled up and only took about 11.8 gal or so.
LRA 12.5.

I think there is space for expansion that is not normally available for fuel, but is calculated into the volume of the tank.

 

[CharlieS]

I think there is space for expansion that is not normally available for fuel, but is calculated into the volume of the tank.

Maybe, but I've done 12+ gal fills into my 12.5 LRA with no magic.

 

[mobi-arc]

You don't want the low point of the p/u tube to be on the very bottom of the tank as it will suck up debris, so there's always going to be leftover fuel in the tank.

 

[kcjaz]

I have backed the left rear wheel up onto a curb (fuel pickup is front right)…

 

[Fisher23]

40 gallon with upgraded pump.

I can’t get the last 2-5 gallons out of mine either, I’ll pump until pump shuts itself off. @Fisher23 just so I understand, to get the remaining few gallons out I should turn the pump back on after it shuts itself off? If this is the case then why does it shut itself off in the first place?

Next time you use and pump until it normally shuts off. At this point you already know from your last fill up how many gallons of usable fuel you have "at this point".

Then when you get home, if you have time the the vehicle power on but don't start the vehicle. (i.e. press the ignition switch 2 times).
Go open up the fuel filler cap. Go turn on the pump and watch it pump the fuel through the filler hole. You will hear how loud the pump is pumping fuel.
If the pump turns off again while still pumping fuel press it a 2nd time (or even 3rd) . and watch and listen to see at what point in time does it stop pumping fuel. Then turn it off.
Then you will know how much usable fuel you have and how many extra times to press the button if desired..

FYI: When the "red light" for the aux fuel transfer controller turns on it is programmed for how many more minutes to pumps fuel. This is adjustable.