How is the diesel tank vented in a 150 diesel?

[Doug32 Member Find all posts View Profile Close Doug32]

The fuel tank in my 2014 Prado has developed a problem with excessive blow-back when filling up. I had issues before which led to the in-tank fuel pump being replaced along with the external fuel filter that connects the main and reserve tanks. I am aware that the 120 series has a vent valve up near the rear diff. Is there any similar vent valve fitted to the 150 series - if so I cannot find it hence this post. Any advice is welcome.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Same place as 120. Above the diff where it is easily seen from the front. The one breather is for BOTH tanks. Easy to get to and to clean. Read the thread on fuel pickup problem in the 150 diesel section. Your earlier problem may well have been related to this issue. It is one of the known causes.. There is mention in the thread of the breather.

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

After mapping out all the lines going to the Main and Sub tanks I don't believe the valve under the body is a breather, but rather a high [air] pressure relief valve (in and out) to protect the fuel tank system. The fuel cap is the major air inlet mechanism as fuel is consumed (it has an easy to open one way valve built into it - try breathing through it :-) Oh, they can block up, too). When filling with fuel the main tank has ~10mm breather across to the sub, then the sub breathes up to the inside of the fuel filler via different hose. Foamy (and hiflow) fuel appears to overwhelm the breather setup as I experience an easy fill up to the brim when I can get low foam fuel.

If you're able to get the tanks to breathe more easily, let us know.

Ian B

[Doug32 Member Find all posts View Profile Close Doug32]

Same place as 120. Above the diff where it is easily seen from the front. The one breather is for BOTH tanks. Easy to get to and to clean. Read the thread on fuel pickup problem in the 150 diesel section. Your earlier problem may well have been related to this issue. It is one of the known causes.. There is mention in the thread of the breather.

Are you sure 404PUG, as I cannot find any such breather on my 150 diesel. It would be great if you posted a picture of the location of the valve.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

No picture but it is there. There are about 3 or 4 hoses clustered together and one of them has a flat plastic bit pushed into a holder up against the floor

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Have a look at the video in post 23 of the fuel pickup thread in Prado 150 diesel. It clearly shows it. The thread is the next one down from this one.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

This is my understanding of this (so hopefully is close enough to help explain what is happening).

I don't think its the tank breather check valve under the vehicle that causes the issue when filling up..

The filling issue is the common vent path that comes up to the top of the filler neck, it has a junction further down where the two tank filler vents join.

If your sub-tank is full/over full due to a transfer failure it can block or restrict the main tank filler vent path and cause the blow back.

Normally the sub tank would empty first and fill last, so under normal conditions when the main is filling its vent can expel the air displaced by the in-coming fuel via the filler neck and also into the sub-tank which is still open via the filler hose so plenty of capacity.

Problems begin If the sub tank is already full, the main is restricted to venting via the small pipe in the filler neck so creates back pressure reducing the speed you can fill at.

If the sub tank overfills and the filler vent path fills with fuel and partially blocks the main tank vent path even more back pressure is created and the air must come back up the filler neck against the fuel flow contributing to excessive foaming ,dropping the fill speed and triggering most pump shut off valves.

I have seen mention that the filler vent hoses can be kinked if installed incorrectly so will give same symptoms but not change when the sub tank is empty.

The tank breather check valve under the rear of the vehicle works in conjunction with the fuel cap one way valve (which only lets air in) to allow the tank to vent out or breath in as the temperature changes and fuel is consumed. If one or both are blocked this can restrict sub to main tank fuel transfer plus fuel delivery to the engine and can normally be picked up when you open the tank cap as there will either be a hiss as pressure is released or air sucked in due to the blockage.

Yellows are the tank breathers that feed to the under vehicle breather/check valve via a T piece.
Reds are the filler vents that feed to the vent point at the top of the filler neck vent pipe via T piece.
Blues are the fuel filler inlets that join at a T piece and connect to the filler neck pipe.

[Doug32 Member Find all posts View Profile Close Doug32]

Thanks ptommo59 for posting your informative and detailed explanation. I now have a better understanding of the issues plaguing me at the moment. (I live too far from a Toyota dealer or competent mechanic to get advice and/or service - hence my post)

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

Thanks PTOMMO59 for your very detailed explanation & photos of how the fuel system works. Fortunately I don't have an issue at present but knowing how it works could help if something goes wrong in future. An invaluable reference.
Thanks again.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Indeed. Helped me solve my problem but knowing how to get going again out in the bush is also critical.You need the various solutions to fix it once you get home under your own steam and not on a tow truck.

[Doug32 Member Find all posts View Profile Close Doug32]

Well I hope I am coming to the end of my problem but have one question relating to where the rubber ring sits on the transfer pump spigot. I don't want to risk getting this wrong as it will mean having to remove the tank again. Can someone confirm I have it correct. See image below.

https://www.pradopoint.com.au/core/i...EAAAICRAEAOw==

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Hi Doug32,

Your image link is not working for some reason so can't see your issue.

Have a look at this parts catalogue info and see if that has enough details FUEL TANK & TUBE | Toyota LAND CRUISER PRADO KDJ150R-GKAEYQ 08.2009 - 06.2015 | Parts Catalogs | PartSouq

[Doug32 Member Find all posts View Profile Close Doug32]

Thanks ptommo59 for your help. Here is a new post which makes more sense - hopefully.

I notice from the above link that there are two O Rings on the spigot at the end of the pump and not just one. The thick one is ...08019 and the thinner is 2328K.
I am unsure whether ....08019 should be at "A" and 2328K at either "B" or "C" position. When we removed the pump there was only the one O Ring ...08019, hence the confusion. Perhaps there is only the one (...08019) on the diesel model and 2328K is for the petrol model. If not then then the 2328Kit was lost in the removal of the pump. I hope this all makes sense.

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

I don't think its the tank breather check valve under the vehicle that causes the issue when filling up..
..Yellows are the tank breathers that feed to the under vehicle breather/check valve via a T piece.
..Reds are the filler vents that feed to the vent point at the top of the filler neck vent pipe via T piece.
..Blues are the fuel filler inlets that join at a T piece and connect to the filler neck pipe.

Ptommo59,
I agree about the under body check valve.
However, (and I might be wrong) I believe the larger pipe in the yellow circle on the Sub is where the breather from the Main tank joins the Sub. The Sub check valve connection (evaporation hose) is the smaller pipe to the rear right in the photo.
Compare with


















Ian B

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Doug32,

Sorry don't have the actual answer on where the missing 2328K O-ring goes (or if its even needed) but the petrol version setup is different as they have an additional pressure regulator and two of the 2328K O rings for this as per this cat illustration

FUEL TANK & TUBE | Toyota LAND CRUISER PRADO GRJ150R-GKAEKQ 08.2009 - 06.2015 | Parts Catalogs | PartSouq

May be the original O ring is stuck inside the hose/fitting that slides over the 08019 O ring and Spacer or is the one you found in the base of the assembly?