Sub Tank?

[cvera Lurker Find all posts View Profile Close cvera]

Can someone please explain how the sub tank works on these?

Is it as simple as fill it up and when the main tank is empty hit the switch for the sub tank so that the green light goes on ?

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Re: Sub Tank?

Simple as that. You will notice a small amount of fuel will transfer to the main tank if its empty, very small amount over a period of say weeks. Till you get use to it you will think beauty I have full subtank, then you will check the guage a few days later and think christ this thing is drinking it, then you will notice the main tank guage has gone up a mill, this will explain it. Steve

[cvera Lurker Find all posts View Profile Close cvera]

Re: Sub Tank?

Thanks guys!

That explains it ! I was thinking where fuel went from my sub tank over the weekend? Granted I did not put much in.....

[xlr8_87 Advanced Member Find all posts View Profile Close xlr8_87]

Re: Sub Tank?

I find with my sub and main tank, if I fill up the main tank with the sub tank not full, the main tank will flow into the sub tank a fair bit. it can increase the sub tank by upto 1/4. If you're not already, make sure you use the sub tank, don't just let fuel sit in it for ages. Have heard of people who never used their sub tank (just kept filling the main and running on that), which can bugger up your fuel pump.

[Thistledo Lurker Find all posts View Profile Close Thistledo]

Re: Sub Tank?

I do a lot of kms and get paid fortnightly so the way I run mine is

when the low fuel light turns on I fill up and top the sub up to $90 regardles to the per ltr price. Then when sub tank gets to full I run it down to 1/2 before changing back to the main tank (or if funds are low between pay days I run the sub tank ) that way I am always running fresh fuel and keeping the fuel pumps in good nick

Also I can take advantage of Low price Wednesday fuel

Phil

[Guest Close Guest]

Re: Sub Tank?

The sub and main tanks are not connected and DO NOT draw or spill fuel from one to the other. Each tanks has a sperate filler neck and seperate fuel lines.

They junction at a couple of solenoids which sit under the body around the vicinity of the passenger seat. They are protected by a plastic cover so you don't normally see them. But trust me they are there.

When you switch over tanks on the dash it switches the solenoids which open the fuel line to the respective tanks.

So the urban myth that fuel transfers from one tank to the other is just that.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Re: Sub Tank?

Hi Wizard I will double check when I get home but I'm sure it even says in the log book about fuel transfer. and if what you say is true then why like others When I have a full main tank but say 1/4 in the reserve after about a week my main guage will be showing just under full but the reserve has gone up ?? I believe when I questioned this before I read in my log book that on start up a certain amount is pumped in to the reserve, reason so is to keep the reserve pump lubricated ?? I will double check when I get home. Not saying your wrong BUT would love to know where my fuel goes from my main tank when I have the switch set down to run on the reserve tank ?? Regards Steve

The sub and main tanks are not connected and DO NOT draw or spill fuel from one to the other. Each tanks has a sperate filler neck and seperate fuel lines.

They junction at a couple of solenoids which sit under the body around the vicinity of the passenger seat. They are protected by a plastic cover so you don't normally see them. But trust me they are there.

When you switch over tanks on the dash it switches the solenoids which open the fuel line to the respective tanks.

So the urban myth that fuel transfers from one tank to the other is just that.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Re: Sub Tank?

Simple as that. You will notice a small amount of fuel will transfer to the main tank if its empty, very small amount over a period of say weeks. Till you get use to it you will think beauty I have full subtank, then you will check the guage a few days later and think christ this thing is drinking it, then you will notice the main tank guage has gone up a mill, this will explain it. Steve

..... Sorry I have this around the wrong way, it will transfer from the main to the reserve........

[VL400 Member Find all posts View Profile Close VL400]

Re: Sub Tank?

So the urban myth that fuel transfers from one tank to the other is just that.

I have been testing this 'myth' with a mate for the past month or so. Both of us have 90series V6 (mine is 1998 and his is 1997), mine seems to have no fuel transfer but my mates def does. Both of us have ran the main tank for 4 tanks now without switching to the sub. We both started with the sub smack on a 1/4. His sub tank is now full and mine is on 1/4 still.

The solenoids must switch both supply and return lines to the selected tank. I suspect that the return line may stay switched to the sub tank for a few monents after startup, however I dont know why mine has no transfer and my mates does.

Next test is to see if the main tank fills or empties when running only from the sub.

[Steve M Addicted PP Member Find all posts View Profile Close Steve M]

Re: Sub Tank?

Be interesting to see your outcome !! Keep us updated as to what happens. Regards Steve

So the urban myth that fuel transfers from one tank to the other is just that.

I have been testing this 'myth' with a mate for the past month or so. Both of us have 90series V6 (mine is 1998 and his is 1997), mine seems to have no fuel transfer but my mates def does. Both of us have ran the main tank for 4 tanks now without switching to the sub. We both started with the sub smack on a 1/4. His sub tank is now full and mine is on 1/4 still.

The solenoids must switch both supply and return lines to the selected tank. I suspect that the return line may stay switched to the sub tank for a few monents after startup, however I dont know why mine has no transfer and my mates does.

Next test is to see if the main tank fills or empties when running only from the sub.

[MRW82 Member Find all posts View Profile Close MRW82]

Re: Sub Tank?

it sounds like your mates soleniod valves on the return line are not working correctly. either they are not switching or the sub tank solenoid is not sealing shut, allowing return line fuel into the sub tank instead of/aswell as the main tank.

I get no noticable transfer in my prado.

the owners manual does state "a SMALL amount of fuel gets transfered from main to sub" to encourage use of the sub tank.

[Taresk Member Find all posts View Profile Close Taresk]

Re: Sub Tank?

I've watched this happen in my Prado over the five years I've had it, it consistently transfers a small amount of fuel to whichever tank is holding the least (up to about 1/2 full).

Because of the transfer I've gotten into the habit of exclusively filling the sub tank (unless it's a long trip), over a few sub tank-fulls my main tank will rise to about half full, at which point I switch to the main and run it until it's down to just above warning light level, then switch back to the sub to repeat the process.

It does work the other way, but it seems that flow from a full main into an empty sub is much slower.

[dhula Member Find all posts View Profile Close dhula]

Re: Sub Tank?

it seams to be that petrols do the transfer thing but diesels don't.
i know my deso doesn't do it

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Re: Sub Tank?

I have a 98 model Prado and when I fill up one tank, a bit of fuel definitely flows over to the other one. It's like there's a small overflow hole between both of filling nosles not far below where you put the fuel pump in to fill the car up. A good indicator is when you've filled up both tanks to the brink when heading off on a long trip and you've switched over to the sub-tank. It takes ages for the fuel needle to start to go down because the main tank is flowing over into it when you hit bumpy sections in the road or track, thus keeping it full until the main tank has dropped a little to where the fuel doesn't reach the overflow level anymore.

I've driven my car more than enough to know how much fuel it uses. When one tank is full and you're using it, the fuel needle does start to drop quickly after filling. But if you've got both tanks full, it does take longer for the fule needle to start dropping.

[Bali Prado Lurker Find all posts View Profile Close Bali Prado]

Hi guys..just jumping on an old thread,but as I am first time owner of a Prado 90 series..I am curious as how to switch over to use the sub tank? Can't find anything on the dash..& don't have an owners manual..can anyone let me know? Thanks..Tony