90 Series Prado Fuel Passage Sub Tank

[patrick_133 Lurker Find all posts View Profile Close patrick_133]

I have an 1996 Toyota Prado, It is my First Prado.

I have owned other Vehicles with Dual Fuel Tanks and have not had this feature, 70 and 80 series Land cruisers, Pajero

The manual Says (attached) that when you drive on the Main tank it Puts fuel in to the Sub tank to force you to use the sub to keep the pump lubricated. (this makes sense)

1st Question) I had just over half an tank of Main when I decided to swap it to sub, I am down to half a tank on Sub, at the same time the Main has dropped down to a Quarter, with out me running on the Main tank at all.

Is this Normal?? seems like it is using from both tanks!


2nd) Does any one know how much gets pumped in to the tank from the other (EG 5lts for ever 20ltrs used

3rd) Can I Disable this feature with out buying a new solenoid, as I like a Sub tank to be a Sub (Reserve, Emergency etc)

4th) When the Sub is Full, and you are running on Main am I looing fuel on the road or what?? where is it going when its pumping it over?

Manual
https://skydrive.live.com/redir?resi...8BA22776%21281

4x4
https://skydrive.live.com/redir?resi...8BA22776%21280

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

Im not sure exactly how much transfers in the way of litres but I do know when I had both my 90's every time I started the car it would transfer from the main to the reserve. When running on main I use to think wholy shit this thing is thirsty till I realized it transferred across as I noticed the reserve tank getting fuller. If the reserve is already full then Im not sure what it does, wether it still transfer but does a loop and ends up back in the main or what ???...Must say I did like the fuel set up better on the 90 then my 120. I liked having control which tank I was coming from. If I was doing some rougher stuff 4wding I would only fill the reserve full and keep about a 1/4 in the main, firstly to stop the low fuel light being on, the other so it gave me a tad more clearance with not having the weight of the fuel in the rear tank....Cheers Steve

[Ian Reid Advanced Member Find all posts View Profile Close Ian Reid]

Will have to check this out. Had my 95 for 13 years and never knew it did this and never noticed fuel transferring.

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

Correct, it will transfer the un-used ( or return fuel) to the other tank. If the other tank is full, it will still return the fuel to that tank, however that thank will just keep filling and overflow into the tank it originally came from via the filler neck.

[JKAF Junior Member Find all posts View Profile Close JKAF]

I'm with Ian. I've had my 95 since 2000 and have never noticed any fuel transfer.
When I fill up I always use the sub tank first. I run it to empty then switch it to the main tank which shows full. The main tank never goes down unless I'm using it.
This could be something with earlier models.

[patrick_133 Lurker Find all posts View Profile Close patrick_133]

Correct, it will transfer the un-used ( or return fuel) to the other tank. If the other tank is full, it will still return the fuel to that tank, however that thank will just keep filling and overflow into the tank it originally came from via the filler neck.

That makes sense, Apart from both gauges are dropping, not one dropping other rising.

That's a LOT of fuel to be transferring, as nearly 80% of the fuel gets returned.

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

I don't notice a change on the gauge but I will run the main tank dry then transfer over to the sub and after a couple of hundred km's I will then fill both tanks continue using the sub tank until it runs dry then flick over back to the main tank, so I rotate tanks. On many occasions whether it be the main tank or sub that has been ran dry after driving on the tank with fuel in it for a couple of days I will flick back to the "so call" empty tanks and get another 20-30 kms out of it. So I really don't know how it works.

[ratsack Member Find all posts View Profile Close ratsack]

I'm not sure how it really works but I never notice any of my gauges change. I normally fill both, use 90% of the sub tank and then change to the main. Should I be doing it the other way around?

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

yep its normal... i didnt like it on mine.... the feature is controled by the engines ECU... havnt delved into it much but it can be stopped... depends on how good you are at car electrics . you wont need another soloniod either

i always use main first as main is the rear most tank.. ( take the weight off the rear over hang first)

[skulldragger Junior Member Find all posts View Profile Close skulldragger]

Mine's a 1998 VZJ95 3.4L V6. I always fill both tanks , run on the main first then switch to the sub. I have never seen the gauge level increase in either tank.

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

My understanding of the system is that a small percentage of the fuel return is diverted to the sub-tank. Just enough to "wet" & lubricate the in-tank pump.
My petrol system returns less than 10 litres per main tank to sub-tank. I have seen a instance where the switiching solenoid failed and did not change the return back to the main tank. The sub-tank overfilled very quickly and then the overflow dumped through the carbon cannister to ground.
In the petrol system at no time is the system designed to feed the main tanks return completely to the sub-tank.

As has been said you should not be using fuel from both tanks
Lee

[patrick_133 Lurker Find all posts View Profile Close patrick_133]

By what I'm reading I should not be loosing/Using any fuel from the main when I'm on the sub tank.

I think there must be something wrong with the ECU and drawing from both, I'm going to run the main dry (don't like doing this) and run on the sub and see what happens.

Then do the same in reverse, Run sub dry and run on main!

[Steevo Member Find all posts View Profile Close Steevo]

I did know this but never noticed any difference in levels. I alternate between the 2 tanks 50/50, use main then swap, use main then swap which keeps ""Hopefully"" all components functioning as they should

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

My bet will be when using main first with 2 full tanks it will do exactly that and won't see any thing unusual. Then when using reserve last again nothing unusual. When doing the other way round starting with 2 full tanks again and using reserve first I bet you will see the main drop a tad even though your not running from the main. I found the main dropped more when doing shorter runs due to me starting and stopping the engine so much..... I may be wrong and maybe my Prado was doing some thing it shouldn't have been doing but I didn't have any fuel issues in the time I owned it (except with LPG another story). I would also reset your trip meter each tank as well and write it down just for curiosity.... Cheers Steve

[patrick_133 Lurker Find all posts View Profile Close patrick_133]

I do reset the trip meter each fill, I don't drive it much find it easier to ride to work only a few km's so takes a bit of time to use all the fuel especially with 150ltrs