Toyota Prado Fuel & Fuel Gauge Issues

[AmyHickey]

I have a 2011 Toyota Prado GXL, i have had the car into the mechanic numerous times to fix the problem but unable to resolve it as of yet 

When trying to put fuel in the car the fuel bubbles up and will only let me put small amounts of fuel into the car as seen in the video below, the fuel gauge is empty at half fall as we let it run out and was still saying half full 

We first thought air in the tank and have taken breather out to let air out, mechanics have then made sure all lines are clear and changed the secondary fuel pump which transfers the fuel to the second tank, they have then changed the Fuel Pump Relay unfortunately we are still no further ahead and they have no idea what else it could be

Has anyone had the same issue or may have an idea on what it might be? 

(Edit it wont let me add videos of the issues ? ) 

[beretta]

The problem is in the venturi sucking mechanism that pulls fuel from the sub tank to the main tank.

Diesel 120 prados have a small sub tank (approx 35L)  and a big main or front tank(145L). 150 Prados have similar but smaller tanks, 150L total

To understand everything you have described you need to understand how the system works. This write up is for the 120, but from what i know with the 150s the system is the same

The fuel pump is located in the front tank and pumps fuel out and through a fuel filter that's located underneath the car next to the tank and straight back into the same tank. When it comes back into the fuel tank module there is a venturi or sucking mechanism that "pulls" fuel from the rear tank to the front. If this venturi is blocked or cracked than the fuel isn't transferred. Common cause of this is dirty fuel, not changing the fuel filter underneath the car, If you replace the entire fuel tank module in the front tank then your problem will be fixed. Or get the mechanic to take the fuel module out again and pull the fuel hose's off the venturi on the fuel module and clean it.

Fuel fill vacuum lock issue again here how the system works

Diesel is sucked into the engine by the injector pump, from the front tank to the engine then back into the rear tank.

If the fuel isn't sucked from the rear tank to the front tank (because of the blocked venturi fuel module issue) then the rear tank becomes overfilled and overflows up the fill tube and trickles into the front tank. Providing there's enough fuel in the system (more than 35L) so all good you can keep driving as long as you have at least 35L in the system.

If the car runs out of fuel, what's happening is the front tank runs out while there is still fuel in the rear tank. 

When trying to fill the car the rear tank is already filled to maximum, fuel flows through the fill tube into the front tank, the front tank breather hose goes into the rear tank. but because the rear is full and overflowing the air has nowhere to go and instead bubbles and blows back up the fill pipe, clicking off the bouser, making it difficult to get fuel in. I found that parking the car on a hill nose down a little helps fill alot quicker.

The fuel tank module is quite expensive $500 plus, so a backyard fix is to put a cheap ebay inline fuel pump on the hose between the 2 tanks and attach it to a switch inside the car. You can flick this on 10minutes before fueling up at the servo and the car will fill without air lock issues no worries. Obviously cant leave this fuel pump switched on all the time because when the rear tank emptys the pump will suck air and burn out. (Which is the reason Toyota designed this venturi fuel transfer mechanism in the first place)

And the fuel gauge obviously doesn't function correctly if the fuel isn't transferred from the rear to the front as designed.