Overfilling main tank with LRA transfer pump

[kcjaz]

In theory, if one were to keep pumping fuel from the aux to the main tank after the main tank is full, the overflow would go up the main tank fill neck tube into the upper box and back to the aux tank. Wouldn't doing this risk fuel getting into the Evap canister/charcoal filter? Anyone actually done this?

 

[BadReligion]

I just finished wiring up the pump and switch on my newly installed 12.5 LRA tank literally 10 minutes ago. I was going over filling instructions with my wife (the 200 is her DD) and she asked the same question.

According to the LRA instructions, they state that "If you happen to overfill the main tank, it will simply drain back down to the auxiliary tank, as the transfer line directs fuel into the main tank fill tube downstream from the fuel filler."

Looking at the LRA filler neck, the vent tubes (from aux tank and from evap canister) sit well above the transfer tube, and above the level of the fill holes themselves, so you would think that fuel would overflow from the main tank filler hole into the aux tank filler hole. I'm sure some additional vapor will go back into the evap cansiter which is probably not good on a repeated basis, but an occasional "overfill" situation should be ok.

 

[Fisher23]

No, this has been discussed in detail before.

 

[kcjaz]

I had searched and found this thread where a member had some issues with leaks and there are a couple posts with people flooding the charcoal canister but it was from over filling the tank at a filling station gas pump.

200 Series LRA Aux tank issues

My 2010 200 series has a 12.5. Gallon Long Range American auxiliary gas tank installed by a local truck shop in San Diego. Too many closed gas stations in Baja. First fill up- only took 9 gallons before pump stopped. Tried to fill to 12.5 and flooded my charcoal canister- replaced and...

forum.ih8mud.com

I didn’t do my install so I don’t have a clear picture in my head of the physical position of the evap canister and charcoal filter but I don’t see how they can be higher than the filler neck. The pic below is from the LRA instructions. If it’s like the pic, there would seem to be risk with overfilling from transfer pump or at the filling station.

 

[Fisher23]

The are some other pictures.
Best to make the breather line from the charcol box a little longer, then loop it over where the breather lines go into the box so it hangs down. Hangs down to let any condensation drip out.
I looped mine so it's higher and above the box tank breather lines.
Then put a sock over the breather to keep dust out.

 

[kcjaz]

The are some other pictures.
Best to make the breather line from the charcol box a little longer, then loop it over where the breather lines go into the box so it hangs down. Hangs down to let any condensation drip out.
I looped mine so it's higher and above the box tank breather lines.
Then put a sock over the breather to keep dust out.

thanks. I can see the benefit of that but that doesn't really prevent getting liquid gasoline in the charcoal filter or evap canister if main tank is overfilled. I think that is the main point you were making in your initial reply to this thread, i.e. don't overfill the main tank.

To go further down the rabbit hole, with or w/o an LRA, when the boiling gas thing happens, and there is literally gasoline pouring out of the filler neck, how is that same gas not flooding the evap canister and charcoal filter. The times I've seen this happening, no one was getting evap codes or anything.

 

[CharlieS]

thanks. I can see the benefit of that but that doesn't really prevent getting liquid gasoline in the charcoal filter or evap canister if main tank is overfilled. I think that is the main point you were making in your initial reply to this thread, i.e. don't overfill the main tank.

To go further down the rabbit hole, with or w/o an LRA, when the boiling gas thing happens, and there is literally gasoline pouring out of the filler neck, how is that same gas not flooding the evap canister and charcoal filter. The times I've seen this happening, no one was getting evap codes or anything.

I second this observation - when I had gas boiling out in South Dakota (clogged vent filter on my LRA) I didn't get codes, and haven't had any since returning home.

I did get evap codes as elevation in Colorado, but it wasn't boiling over at the time.

 

[kcjaz]

So as I go deeper yet down the rabbit hole, I realized I don't really now anything about how the evap/emissions control system works. So I googled it and found a youtube video to 'splain things to me:



Not a 200 but at about 5:40 into the video, as he's dissecting a fuel tank, the guys says "so here we have the fuel check valve" and the light bulb goes off in my head. The valve is actuated with a float and is designed to stop liquid gas going into the evap canister/charcoal filter. I was thinking this was just a simple open vent line. Thinking about it, it really probably couldn't be an open vent line as the system is intended to be closed and not leak gas even of the car has rolled and is upside down. I assume our 200's have a float actuated check valve in the main tank preventing liquid from reaching the evap canister. Can anyone confirm this? I looked for the part but can't find anything. I imaging you can't buy that part because there is no way to replace it if its sealed in the tank.

If we have that valve, that doesn't mean you want to purposely over fill the tank, but it would mean the evap system is designed to prevent damage should this happen. This probably also helps with the boiling gas thing not sending gas into the evap canister.

 

[Fisher23]

If you turn on the transfer pump and forget to turn it off then the fuel will fill up the main and then over flow into the filler area and back into the aux fuel tank. It's not going to effect the canister. I've done this a few times on different vehicles.

Fuel boiling at altitude is a different subject which I'm not really familiar with. I would think it the same problem with or without an aux tank, just possibly amplified.

Now on my "to do" list is: The controller has a white and black wire you can hook up so the main will automatically refill from the aux tank if between 1/4 and 3/4 levels. That is it will turn on the transfer at 1/4 and turn off at 3/4. The transfer controller unit is programmable. Someone told me these threads before which wire to tap into, but I'll have to pull the dash apart again to connect it up.

As for the canister it's all one unit. It's a pain to swap out as it is above the aux tank.

 

[kcjaz]

Now on my "to do" list is: The controller has a white and black wire you can hook up so the main will automatically refill from the aux tank if between 1/4 and 3/4 levels. That is it will turn on the transfer at 1/4 and turn off at 3/4. The transfer controller unit is programmable. Someone told me these threads before which wire to tap into, but I'll have to pull the dash apart again to connect it up.

That is interesting. One thing I noticed when transferring fuel to the main tank was the lag in the main fuel gauge reading. It stayed pretty close to the starting level (~1/4 tank) for more than 10 minutes then jumped to 3/4.

 

[Fisher23]

Yes it does that. I usually turn it off when it reads 1/2 then look down a little later and it says 3/4.

 

[Desert Yeti]

I have over filled mine by accident. This is my second 200 with an aux tank and this one is the 24 gal LRA. It smelled like gas for weeks and I got codes for about 2-3 months. No code now in over 6 months and no gas smell anymore.

 

[kcjaz]

I have over filled mine by accident. This is my second 200 with an aux tank and this one is the 24 gal LRA. It smelled like gas for weeks and I got codes for about 2-3 months. No code now in over 6 months and no gas smell anymore.

Did the codes activate “limp mode”? Just cleared them and moved on? How often did the codes keep coming back over the 2-3 months?

 

[Fisher23]

I get codes occasionally. They are never limp mod codes but they will turn on the engine check light. They are EPA codes like purge valve too slow or too fast, or not within parameters. Usually on a cold day when the main is low on fuel and the aux about 1/2.

I have one of those blue tooth OBDii plugs with an app on my phone to clear the codes when they occur.
The OBDii is also good for monitoring Transmission temperature.

 

[CharlieS]

I always stop filling at the pump shut off (sometimes, only rarely, under-filling it, unfortunately) and only turn the gas cap to the first click. I've never had evap codes except that one time in Colorado at elevation that I cleared with the OBDII reader I carry in the cargo boxes.

 

[kcjaz]

I run OBD Fusion on my head unit so seeing’s codes and clearing them is easy. Maybe I’ll look to see what evap system PID points there there are and build an EVAP dashboard for fun.

 

[Fisher23]

What head unit is that?

 

[kcjaz]

What head unit is that?

16” Tesla style from EC Offroad. Same units are made (packaged) by Phoenix Automotive.

Tesla head unit install (pre2016 LC) - first impressions and a couple bugs to figure out

forum.ih8mud.com

 

[Desert Yeti]

Did the codes activate “limp mode”? Just cleared them and moved on? How often did the codes keep coming back over the 2-3 months?

It did not ever go into “limp mode”. But when there are codes you cannot use 4lo. I have a Bluetooth dongle that is always plugged in so I could reset if needed.

 

[bloc]

I’ve never seen the float valve in a 200 but my 80 definitely had one. Correct on it preventing overflow and also stopping flow in the event of a rollover. I suspect the people getting killed charcoal canisters in places like Moab are from hot fuel as well as the sloshing that occurs on bumpy trails. I can imagine this easily moving a float system around depending on the configuration.

I dug up some pictures of the 200 fuel tank and you can see at least where things hook up. Three lines, large tank fill is obvious, medium tank vent as well.. not sure about smallest line since it isn’t at the top. Also note on the bottom picture the deep curved slot molded into the tank with a narrow open area toward one side. Pretty sure this is to let fuel flow rearward on uphill sections, then get caught in that scoop for steep descents.