sub fuel tank syphon into main ?

[warren Lurker Find all posts View Profile Close warren]

I am a new member to this site and dont claim to understand half the rules so please bear with me.
I have a 98 Prado v6 auto.
Three weeks ago I ran my main tank to empty in preparation to fit LPG 5 weeks down the track. The "low fuel" light was on full time then. Slowly but surely the main fuel gauge is creeping up off empty mark and "low fuel "light on main tank is now off. Is it possible that small amouts of fuel are running or syphoning from the sub tank to the main tank?
If this is the case then estimating fuel consumption becomes difficult unless filling up sub tank and only using main tank to calculate?
Please advise if anyone has had this problem before?

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

When you run the car with the main tank the excess fuel is returned to the sub tank . When you run the car on the sub tank the excess fuel is returned to the main tank . Toyota did this so neither tank is run dry and the pumps don't run dry or dry out. To work out your fuel usage you would have to fill both tanks then run the car for a while then refill both tanks because you will have no way of knowing how much fuel is going back and forth between tanks.

[warren Lurker Find all posts View Profile Close warren]

Thanks for this very useful information. It makes good sense to keep fuel in the tanks. In removing the main tank for gas fit soon, would it be worth keeping the main tank pump for a spare? could it fit the sub tank setup at a later date?
Regards

[97RV6 Lurker Find all posts View Profile Close 97RV6]

Sub Tank

When you run the car with the main tank the excess fuel is returned to the sub tank . When you run the car on the sub tank the excess fuel is returned to the main tank . Toyota did this so neither tank is run dry and the pumps don't run dry or dry out. To work out your fuel usage you would have to fill both tanks then run the car for a while then refill both tanks because you will have no way of knowing how much fuel is going back and forth between tanks.

Thanks Raydes

I have just brought a Prado and was trying to work out why the sub tank was going up seemed a bit weird.

I know most electronic fuel pumped injection systems have a flow back to the tank to allow cooling of the fuel pump, but usually it is back to the same tank the fuel is being drawn from.

Now I know it is not faulty.

I have mine booked in for injected gas and was trying to get some base data for economy.

Cheers :lol:

[warren Lurker Find all posts View Profile Close warren]

97rv6
I too, had my 98 v6 booked in for injected gas ($5000) in a weeks time, expecting to get within plus 10% of petrol consumption.The fitter has just now told me that new info shows that these earlier models do not have a oxygen senser and therefore we can not get the full potential from an injection system as far as automatic adjust to suit conditions. I have decided to go for standard vapour system ($3500) and expect to get around plus 20% petrol consumption.It will be interesting to see how our results compare.
Regards

[97RV6 Lurker Find all posts View Profile Close 97RV6]

97rv6
I too, had my 98 v6 booked in for injected gas ($5000) in a weeks time, expecting to get within plus 10% of petrol consumption.The fitter has just now told me that new info shows that these earlier models do not have a oxygen senser and therefore we can not get the full potential from an injection system as far as automatic adjust to suit conditions. I have decided to go for standard vapour system ($3500) and expect to get around plus 20% petrol consumption.It will be interesting to see how our results compare.
Regards

I am a bit surprised to hear about the lack of oxygen sensor, I will have to check that out. Even my 1984 Nissan has an oxygen sensor ???

I am going for the sequential injection and believe ( because I have been told) that it would allow for best result, maximum power and efficiency my guy is charging $4,400. Still a few weeks away before fitting. Going foa 75lt useable.


:wink:

[Beast2h Member Find all posts View Profile Close Beast2h]

there is no oxygen sensor or cataletic converter of the early v6's they have a manual adjuster thing(not sure wat or how it works) in place of the sensor that is mounted up of the drivers side guard in the enging bay!

[Guest Close Guest]

What i dont under stand...

why dose my prado have a switch to change to sub thank then i can not see any hoses going from main tank too sub tank only the main fuel lines too the motor??