LRA Aux leak?

[OldCarSmell]

Anyone else dealt with a (presumed) gravity leak in their LRA Aux Tank? No fuel spillage that I’ve noticed at all, but I can lose as much as 5-6 gallons of fuel between fill ups without activating the pump to move the fuel from reserve to main tank. My tank is two years old and was purchased prior to LRA offering an upgraded pump. Not sure where else in the system the leeching could be happening.

[PFA, east of the Alvord Playa, out playing in the 200]

 

[george_tlc]

On my 80 series the fuel transfer unit from the sub to the main is a pump and a fuel valve/solenoid. Both have to be energized for fuel to flow. The fuel valve/solenoid is to prevent gravity transfer, i.e. siphoning. This due to the sub being somewhat higher than the main.

Not sure on your 200 what the setup is. But siphoning can definitely happen and would slowly transfer fuel from your sub to main if the conditions are 'right'.

cheers,
george.

 

[OldCarSmell]

On my 80 series the fuel transfer unit from the sub to the main is a pump and a fuel valve/solenoid. Both have to be energized for fuel to flow. The fuel valve/solenoid is to prevent gravity transfer, i.e. siphoning. This due to the sub being somewhat higher than the main.

Not sure on your 200 what the setup is. But siphoning can definitely happen and would slowly transfer fuel from your sub to main if the conditions are 'right'.

cheers,
george.

Thanks George. Curious what conditions might cause siphoning in your estimation? LRA’s site and manuals mention the potential for a gravity leak if the transfer pump is not at the appropriate height or angled correctly. I went back to install shop, had them put it on the lift, we dropped the spare and inspected and everything matches 1:1 from the install manual in terms of written instructions and the included photos for reference.

 

[george_tlc]

Anything that has the sub (and it's 'outlet' above the the height of the main would siphon through the pump. Also if you have hills in your area, the sub could be higher than the main when heading downhill.

Many pumps will allow fuel/liquid to go through them even if not powered if there is a head on one side. Hence the OEM toyota setup on the 80 having a fuel valve/solenoid in series with the transfer pump.

Reminds me of a mate that had retrofitted a subtank to his old 40 series since he installed a V8 and needed the extra fuel capacity. The first run he was boasting of his excellent fuel mileage - until he found that his sub had siphoned into his main

How long does it take to 'lose' the 5 or so gallons? Have you noted improved fuel economy (from the main) ? 5 gallons leaking on the ground would be extremely obvious, along with serious fuel smell.

cheers,
george.

 

[OldCarSmell]

No fuel smell fortunately, so my sense is I'm not losing fuel outside the tanks. I think it would be noticeable as I tend to park in the same places most days and I never smell fuel. The "loss" can happen over the course of a week or two and it ranges from a gallon or 2 up to 5 or 6. I've not gotten a good handle on a pattern of siphoning/loss that could indicate driving conditions that contribute; my driving can be highway or town, paved mountain roads or trail, depends on what we're up to week over week. But there is consistent loss out of the aux tank. Each time I fill up my main tank I top off the aux tank and it usually takes 1.5-6 gallons to fill. We live in wildfire country so in summer I aim to keep the aux tank filled and drain and re-fill the main tank in case we need to hook up the trailer quick and hoof it out of town. I don't know much about the pump that came standard on the LRA 12.5g Aux tank, other than having seen many a post complaining about its low quality and noisiness; LRA has upgraded the pump since I purchased my kit to what I believe others (like Slee, Ed Martin, and some savvy shade tree mechanics) installed as an upgrade. I wonder if the new one has a similar valve/solenoid to prevent/better limit siphoning. Amazing to me that a pump installed for this kind of purpose would be so flawed to allow half of the tank's contents to siphon through. We installed this for towing and extended backcountry travel and right now it's too unreliable to bring into the backcountry other than assuming I have 36.5 gallons of fuel to start.

 

[OldCarSmell]

PSA: I chatted with Aiden at LRA and it is likely that either a filter (Toyota paper filter in fuel line, or LRA filter before charcoal) are clogged and this causing pressure buildup and siphoning; or that the one-way valve in the fuel pump is less than sufficient for the job (the reason LRA upgraded the pump in this kit a year or so ago) and that is causing siphoning. Aiden has experience with the 200 and offered several helpful options to remedy this: he will send me instructions for cleaning out the filters; he will send at cost the upgraded pump (the original pump is not covered under warranty, but is reasonably affordable from a third party or through LRA, and through LRA comes with some additional fittings that may or may not be necessary) with some extra fuel hose and instructions for install. Hopefully I can tidy this up on my own without paying shop fees! I'll follow up and provide details and results for posterity.