Prado diesel 120 series fuel tank puncture

[Billx Lurker Find all posts View Profile Close Billx]

I was in the middle of the Gregory National Park last month when I discovered my Prado was leaking diesel from the forward fuel tank. There was a small .5 cm hole in the protective steel protecting the tank from below. It looked like a steel rod had somehow gone through the steel from the rear and punctured the tank inside, perhaps when I was reversing although the real cause is a mystery as it was too small for a star picket.

I made it to Kununurra where Toyota Broome did a good job and plastic welded up the actual tank( which apparently is plastic).

However I don't understand the actual configuration of the two tanks. I assume I punctured the secondary tank and the fuel gauge would not have registered the loss until the primary tank had been exhausted and the system started to use the secondary tank. If I had punctured the primary tank then I assume all fuel could potentially be lost as it drained out of the primary and then the secondary tanks. However this is a guess on my part which begs the question-

Does anyone know how they are configured-i.e. which one fills up first, whether there is one or two fuel gauges, how the measurement system works, what is the mechanism to switch over to the second tank, which tank sits higher and if you get a leak in one of the tanks how does it affect the other one?

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

Which tank is the primary and which is the secondary is up for debate, fuel is drawn from the front (plastic) tank and as that is used fuel is transferred from the rear (metal) tank, meaning the rear tank empties first. However the rear tank is the larger of the 2. 93 litres compared to 87, so you could call either the "primary" tank depending on your point of view.

I put a hole in my rear tank years ago in my first 120. A stone got lodged between the stone guard and the tank and wore a hole through it crossing the Tanami, I only noticed it when I filled up at Halls Creek and it started leaking out all over the ground.

In my case the rear tank was already empty when the tank was punctured, as there was no evidence of fuel having leaked, so it had no immediate effect on my touring range, was handy given the 1100km drive between fuel stops on that trip.

In your case, with the front tank punctured, if that wasn't stopped it would continue to draw fuel from the rear tank and empty you out completely.

As for the filling, the rear tank has a straight (ish) run to the tank, where as the front tank the fuel needs to take a 90 degree bend, so if you partially filled the tanks the rear would likely fill first, but once on the move the fuel would get transferred to the front tank.

Hope that makes sense and helps.

Cheers Andrew

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

Very good answer Andrew.

I can add that I'm relatively sure the front tank fills first.

[Billx Lurker Find all posts View Profile Close Billx]

Andrew,

Thanks, very helpful. Any suggestions on how the fuel gauge system works?

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

There is a separate sender in each tank. When you use the first (rear) tank the fuel gauge will drop to around half on the gauge, indicating you have used half your fuel. Once that tank is empty the gauge jumps up to full and the 90 liter light comes on, the gauge then drops until the low fuel warning comes on with 15 lts left. It's an overly complicated system but easy enough once you understand it.

Cheers Andrew

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

Great description!

I put a huge dent in my main tank yesterday when I slipped in to a rut and landed on a boulder. Fuel gauge was doing some pretty crazy things!
Just realised the main tank is plastic which is a big win! Should pop back out once I swap out the dented guard! Off to the wreckers!

- Ben

Which tank is the primary and which is the secondary is up for debate, fuel is drawn from the front (plastic) tank and as that is used fuel is transferred from the rear (metal) tank, meaning the rear tank empties first. However the rear tank is the larger of the 2. 93 litres compared to 87, so you could call either the "primary" tank depending on your point of view.

I put a hole in my rear tank years ago in my first 120. A stone got lodged between the stone guard and the tank and wore a hole through it crossing the Tanami, I only noticed it when I filled up at Halls Creek and it started leaking out all over the ground.

In my case the rear tank was already empty when the tank was punctured, as there was no evidence of fuel having leaked, so it had no immediate effect on my touring range, was handy given the 1100km drive between fuel stops on that trip.

In your case, with the front tank punctured, if that wasn't stopped it would continue to draw fuel from the rear tank and empty you out completely.

As for the filling, the rear tank has a straight (ish) run to the tank, where as the front tank the fuel needs to take a 90 degree bend, so if you partially filled the tanks the rear would likely fill first, but once on the move the fuel would get transferred to the front tank.

Hope that makes sense and helps.

Cheers Andrew