Twin Fuel tank operation ??

[IvaN Idea Lurker Find all posts View Profile Close IvaN Idea]

Hi everyone.

I just bought a 2008 120 series, 4 litre with a 5 Speed Auto with 116k on the clock, 1 week ago.

My question is :

How does the twin tank system operate / Display on the gauge ?

Reason I ask this silly qn is as I picked up the vehicle it had 3/4 tank showing on the gauge (green 90L light ON), I filled 100L worth of fuel when the needle was on EMPTY and when I started it up at the Servo the gauge needle went up to just under 3/4 .... but now with NO green 90 L light illuminated.
Tonight as the needle got down to HALF tank, still with NO green 90 L light illuminated and approx. 10-15 klms later the gauge went back up to FULL but this time the green 90 L light was ON !

Is this correct, or am I correct thinking that the MAIN tank fuel sender is faulty ?

Another thought I had is this :
Does the gauge sweep down to only halfway (indicating half capacity of 180 L which = 90 L), and that's why it bounces back up to full WITH the 90 L light now ON, indicating the start of the remaining tank = 90 L (as the 90 L light kindly reminds you).

Hope that makes sense ?

Basically, I am worried that ive got a newly bought vehicle with a Faulty Main tank level sender, therefore prematurely switching over to the 2nd tank.

Thanks,

Ivan

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

Jj

Another thought I had is this :
Does the gauge sweep down to only halfway (indicating half capacity of 180 L which = 90 L), and that's why it bounces back up to full WITH the 90 L light now ON, indicating the start of the remaining tank = 90 L (as the 90 L light kindly reminds you).

Hope that makes sense ?



Ivan

The car is working correctly. This is exactly how it works.

Just treat it as one big tank. When the green light is on you have 90 litres (give or take) left

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

Yeah as R4ndll said, it's all working as it should. The first tank ( the rear one ) is actually 93 litres, the front tank is 87. So when the green light comes on you are actually more than halway through your fuel, the fuel light will come on with 15 litres left.

The fuel gauge is overly complicated, but you get used to it.

Cheers Andrew

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

I have a pdf copy of Prado 120 fuel tank diagram and a detailed advice on how the system works however, they are too big to post on forum.
If you want a copy send me a pm

[IvaN Idea Lurker Find all posts View Profile Close IvaN Idea]

I have a pdf copy of Prado 120 fuel tank diagram and a detailed advice on how the system works however, they are too big to post on forum.
If you want a copy send me a pm

PM sent Pedro,

Thanks everyone for a ... I was starting to think i already had an expensive diagnostic task ahead ! .... but with all your combined info, its kept my sanity in check !

Cheers,

Ivan

[Razorback81 Advanced Member Find all posts View Profile Close Razorback81]

Hey Pedro

i have sent a PM as well

[Pradonut Lurker Find all posts View Profile Close Pradonut]

It's interesting that this has come up just now as last week coming back from Brisbane to Perth I stopped 20k's from Broken Hill with 3/4 of second tank of fuel still showing. I remembered reading of similar occurances and twigged pretty quick what had happened, I had a jerry can extra and threw that in, basically had to carry second tank as unusable to get home.
As an added inconvenience with the second tank full it seems the system won't vent corectly when you refuel and it takes ages at the pump.
Mines a 1kz so I think mine just uses jet pump to draw from rear tank to front so my first thought is that the venturi in the rear tank is blocked.When I got home I removed the return line from the injector pump and back blew the line and refueling today was normal, problem now is I don't trust the system til I find something wrong.
PM sent to Pedro, I suspect there is a dodgy check valve, just not sure where to look.

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

Pradonut,
Did you get my pm I need your email address so I can make attachments

[Pradonut Lurker Find all posts View Profile Close Pradonut]

Done.
Thanks Pedro.

[Razorback81 Advanced Member Find all posts View Profile Close Razorback81]

It's interesting that this has come up just now as last week coming back from Brisbane to Perth I stopped 20k's from Broken Hill with 3/4 of second tank of fuel still showing. I remembered reading of similar occurances and twigged pretty quick what had happened, I had a jerry can extra and threw that in, basically had to carry second tank as unusable to get home.
As an added inconvenience with the second tank full it seems the system won't vent corectly when you refuel and it takes ages at the pump.
Mines a 1kz so I think mine just uses jet pump to draw from rear tank to front so my first thought is that the venturi in the rear tank is blocked.When I got home I removed the return line from the injector pump and back blew the line and refueling today was normal, problem now is I don't trust the system til I find something wrong.
PM sent to Pedro, I suspect there is a dodgy check valve, just not sure where to look.

HEy Pradonut
i read on here somewhere there is a wire/plug on top of the tank that looses it connection
you can access under the LH middle seat
there is a thread on here just dont know where

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

HEy Pradonut
i read on here somewhere there is a wire/plug on top of the tank that looses it connection
you can access under the LH middle seat
there is a thread on here just dont know where

Did a search and this might be it
http://www.pradopoint.com/showthread...fuel+tank+wire

[rooboy4277 Lurker Find all posts View Profile Close rooboy4277]

Pedro
Could you send a copy of this to me at
[email protected]

regard
rooboy4277

[stanmiko Member Find all posts View Profile Close stanmiko]

...the fuel light will come on with 15 litres left.

The fuel gauge is overly complicated, but you get used to it.

Cheers Andrew

Andrew, is this something that has been verified by Toyota, or are you speaking from experience? The reason I ask is that yesterday, mine was showing fuel light for quite some time and I had travelled approximately an additional 60km after the light came on before I refuelled. Interestingly enough, she took 164 L, so even after all that, I STILL had approx. 16 L left in the tank.
Now... on top of this, I seem to find it switches over to the sub tank after I have covered about 1000 - 1050km. THEN I only get approx. another 600- 650km from the sub tank till the light comes on. I have heard stories of sender units being a bit erratic, so I am considering replacing both.

Any thoughts?

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

That's because by the time the 90L light comes on you usually have burned through more than that sometimes as much as 110 litres. It's not a precise function. Mine regularly goes through 100 before the light comes on. And, in all my travels around and across Oz I have only had the low fuel light come on once.

[Hogey66 Senior Member Find all posts View Profile Close Hogey66]

Mine goes the other way. Light comes on after about 70ltr gone. Usually fill it up around then if we go to mackay as it's about 20c/ltr cheaper than where we are.