Fuel Pickup Problem

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

Hi RPP,

I have been watching both tank levels and the pump turn on/off parameter a bit more intensely over several weeks and it seems that when the rear filter is new the main tank stays topped up to full level (83L on my SG2) until the sub empties.

But mine did same as yours towards the end of the 20,000 km rear filter service interval and dropped the level on the main down to about 78L with about 20L remaining in the sub-tanks (It still steadily emptied the sub before starting further on the main).

So my assumption is as the rear filter gets restricted it takes longer for the venturi pump to transfer fuel across and may be sufficiently less that the engine fuel usage under some conditions to start draw down on the main tank, but as you say it will continue to try to catchup until the sub is emptied.

Definitely given your remote adventures I reckon changing the pump out as insurance at the 150,000 Km recommended interval or as soon as practical after is a good idea.

Have wondered if when there is a transfer issue you could disconnect the line from the sub-tank pickup and insert a small 12V electric fuel transfer pump with hose inline to the main rather than a siphon as a backup and this could also be used to empty jerry cans if your don't like holding them up to the filler :-)

Good analysis ptommo59,
next time I see the fuel xfer anomaly I'll correlate it with the age of the filter. I had assumed that the fuel breather valve was clogged (who cleans that anyway) and that created a partial vacuum in the subtank hindering fuel flow under the right conditions
I'm not worried when remote tho'.
I've experienced the anomaly in the middle of the Simpson Desert and the Carson River Track. I carry enough spare fuel (ie 20l) to top up the main-tank and get back to civilization, plus a siphoning hose as another fallback. I can defer the rigmarole and cost of replacing the pump/venturi assembly at 150K to after 200k.

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

OK in a Diesel version:

The in-tank pumps only role is to act as a circulation pump drawing fuel from the main tank, circulating through the rear filter back through the venturi pump in the main tank and repeat. The pump is cycled on and off by I think the body ECU as needed. Even when the sub has been emptied there is return fuel from the engine fuel rail put back into the sub-tank so it still needs to be turned on periodically to empty this.

The venturi pump syphons the fuel from the sub-tank via a direct line so the only reasons it will not transfer is insufficient flow through the venturi pump (pump not working or blocked filter), the fuel line between tanks or pickup is blocked so can't draw fuel, or the breather is blocked so can't draw replacement air into the sub-tank.

The same thing happened to our 2004 V6 where it ran out of fuel back in 2017 just outside Port headland with just under half of second tank left. Funny you mention the breather, once we got going by filling up both tanks, we stopped in Newman to refuel and when the fuel cap was removed there was a rush of air out or into of the filler, Didnt take notice of it at the time as put it it down to the 40 degree day we had. We got back to Perth ( lucky it was a return trip from Fitzroy crossing) just by ensuring we only ran on main tank.
Once we got home I took it around to our mechanic who suspected it to be a cracked venturi pump assembly ( same diagnosis from PH Toyota but they couldn't look at it for 3 weeks). He dropped the tank and removed pump and cleaned out insides. As a precaution he also dropped second tank and cleaned that as well. He couldnt find any fault with pump or tank and actually ran it on the hoist with the return line going into a drum to simulate the point in fuel level where it stopped and actually on last test ran until second tank was empty. He could not fault the system and it hasnt occurred again since.
The though of it possibly being a blocked breather has me thinking that may have been the cause in our case.
Had our mechanic stumped and he was the guy who told us to top up tank to get going and fill both tanks as he had seen a similar problem as ours but as I mentioned in our case the pump wasnt the issue. We had done the previous day before it stopped, the return trip to cape leveque which was in its normal state back then of worst corregations i had ever driven, and I had done that road many times before when I used to service the old lighthouse up there.

https://www.pradopoint.com.au/forum/...ters-and-stops

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

Hmm. More correlation with corrugations and problems.

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

Sparksy,

Just for info as some on here may not be aware the Petrol fuel tank and delivery system is different in the way it works to the diesel version.

The in-tank pump in the petrol vehicles is the primary fuel pump to the engine via the engine bay fuel filter to the fuel rail and circulates fuel not actively being consumed by the engine back into the main tank via the venturi pump (partly this keeps the fuel cooled as it doesn't spend much time sitting in the fuel lines and rail).

The returned fuel going through the venturi is used to draw fuel from the sub-tank into the main and there is no rear filter involved.

Same issues as the diesel version occurs in relation to stopping or restricting transfer across if the fuel tank vent system gets blocked.

The petrol in-tank pump unlike the diesel version is working the entire time the engine is running so is more susceptible to wear out (not certain if that is taken into account in the recommended service/replacement intervals or the petrol version pump has a different design that caters for the 100% duty cycle with equivalent reliability to the diesel version).

When it does fail or path to/from engine get restricted the engine stops or can suffer in performance due to fuel starvation and/or excessive fuel temps.

Hope this is useful info :-)

Edit: The same issue also exists in relation the inlet to the bottom of plastic housing on the in-tank pump assembly getting blocked off causing the engine to run out of fuel when there is almost half a tank left in the main. So topping up so level is over the upper edge of the housing will get things going again until it reaches the same point and you have to repeat.

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

And an update. The post trip service was done today by my Prado owning mechanics .As part of this all 3 fuel filters were changed and ALL, including the rear one were CLEAN. BUT....... the common breather for the 2 tanks on the 150 diesel was totally blocked with mud dust and general crap. Removed, cleaned and checked. On the 5 km drive home I could see on the Scangauge that fuel was flowing MUCH faster from the sub to the main tank. Fingers crossed that the issue is resolved. I will know in about 400-500 km when the tanks are down to about 1/3-1/4 full. What is the lesson here? Replace the rear filter before any extended trip especially if it has done more than 10 K km or will by trip's end. After market much cheaper than genuine. Clean and check that easy to get to breather. Carry extra fuel if going remote. Fill up when the opportunity arises in remote areas so this doesn't. happen to you especially if you are likely to get into that 1/4 - 1/3 tank range. Paying a bit more for fuel is worth it in the scheme of things and helps to keep the remote fuel stations open as well.
As to starting the dead car, 20 litres from a jerry will nearly all go into the main tank [have a look underneath- main is filled first and then overflows into the sub tank.]. Turn on ignition [not to start- just to get the dash lights on] . leave it on and then use the hand pump on the main filter until it is hard. Car will start and you have up to 200 km range.. Read this whole thread and have a look at the links to Fourby4 Diesel that you see there.

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

And an update. The post trip service was done today by my Prado owning mechanics .As part of this all 3 fuel filters were changed and ALL, including the rear one were CLEAN. BUT....... the common breather for the 2 tanks on the 150 diesel was totally blocked with mud dust and general crap. Removed, cleaned and checked. On the 5 km drive home I could see on the Scangauge that fuel was flowing MUCH faster from the sub to the main tank. Fingers crossed that the issue is resolved. I will know in about 400-500 km when the tanks are down to about 1/3-1/4 full. What is the lesson here? Replace the rear filter before any extended trip especially if it has done more than 10 K km or will by trip's end. After market much cheaper than genuine. Clean and check that easy to get to breather. Carry extra fuel if going remote. Fill up when the opportunity arises in remote areas so this doesn't. happen to you especially if you are likely to get into that 1/4 - 1/3 tank range. Paying a bit more for fuel is worth it in the scheme of things and helps to keep the remote fuel stations open as well.
As to starting the dead car, 20 litres from a jerry will nearly all go into the main tank [have a look underneath- main is filled first and then overflows into the sub tank.]. Turn on ignition [not to start- just to get the dash lights on] . leave it on and then use the hand pump on the main filter until it is hard. Car will start and you have up to 200 km range.. Read this whole thread and have a look at the links to Fourby4 Diesel that you see there.

One proviso regarding that hidden fuel tank breather valve.
I've cut one open. Its a bidirectional valve that exhales through a larger opening than it inhales through. The pinhole inhale circuit would clog up easily when driving dusty tracks.
However, this is handy when driving through wheel deep creeks, as the tanks won't inhale water when they instantly cool down.
These days I don't clean/replace it anymore.

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

Well bugger! I thought that I had it solved with all filters replaced AND that little [blocked] breather cleaned and cleared. Today I finally had done enough kms to get the gauge just below the 1/4 mark and the Scangauge showing zero in the rear tank and 35-45 l in the front tank [the reading bounces around a bit]. It stopped! Same fix: added about 10-15 litres, ignition to on position, pump the primer until hard- about 8-10 pumps. It took 2 goes of this but away it went. This clearly means that it is a fuel pickup problem in the main tank when it gets down to about 40 litres left because: all filters brand new, breather clear and clean, no trouble filling the 2 tanks, the venturi is working because all fuel empties from the rear tank to the front main tank quickly at about the current consumption of 11 l/100km. This means it is a tank out job. At 7 years and 84000 km I am not stuffing around trying to find out what is wrong with the pickup and O rings etc. The whole unit will be replaced. Fortunately the part for the 150 diesel is about $650 vs about $1300 for the 120 plus the labour of pulling the tank in and out which I gather is a several hour job. In the meantime I will keep a 20 l jerry in the car until it gets fixed next week. The problem with this fuel issue is that there are about 4 or 5 potential causes you have to work through before you know your specific cause. It would be a simpler problem if Toyota had left a big enough hole in the floor to get the fuel pickup out without dropping the main tank as you could in the 80 series. Dumb. Further report to come when it is fixed and fuel run down to yellow light [which is about 20 litres to go.]

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

Sounds very much like the inlet at the bottom of the plastic shroud around the base of your in-tank transfer pump has become blocked off, so fuel in the pickup area has to come from over the top which would equate to when above approx 1/4 tank remaining mark.

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

Still not done. My local guy decided he was not up to doing the tank out job due to having failed to cure the problem on another customer's car and was unwilling to risk it again. Fair enough. I am certainly not in a position to pull the tank out myself so I will have to hunt around a couple of the local 4wd places to see if anyone has done one. I am still planning to get the whole unit replaced as it has to be the source of the problem and the big cost is the labour. Does anyone who has had the front/main tank on a 150 diesel out have a handle on how many hours it is to r and r the tank and how long to r and r the whole sender pump unit so I can get an idea of the labour cost. I understand the whole sender pump unit is about $650 ish for the 150.

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

This video is of a guy doing his on ramps in his driveway so a bit harder than in a workshop but should give you a bit of an idea of what is involved How to remove fuel tank on a 2012 Prado - YouTube

EDIT: A couple of other videos that may be of interest on the pump function and access (a couple are 120 related but similar enough to 150 to give you an idea)

2010 Toyota Prado 3.0Ltr diesel with a fuel transfer system issue - YouTube
THE PROBLEM - THE SOLUTION? - YouTube
Prado 120 dual fuel transfer failure - YouTube

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

Thanks Ptommo. I may have had a crack at that years ago but the body and age says no! now. So I am guessing that 3-4 hours labour is probably reasonable given the fiddly nature of the job. Interestingly he didn't appear to open the hatch/hole in the floor under the seat.

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

I assume you would only need to open the hatch hole if you want to access the connector to check it is connected, check power/wiring continuity to it, do pump or sender resistance checks, or remotely power the pump during faultfinding/testing.
If you know you need to pull the pump assembly its no help as the tank needs to be dropped and everything can be accessed once you have done that.

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

Further update. Whole unit replaced by Toyota today Whole job about $1500 and 4 hours plus. I have the old unit and it looks as clean as a whistle as far as I can see without dismantling it. The mesh at the bottom looks new. When I get a chance I will pull it apart BUT at first glance I suspect Detjan in post 14 is on the money! That little diaphragm at the bottom as in post 38 was OUTSIDE of the big swirl pot and thus likely blocking the only entry into the swirl pot other than over the top. I suspect low fuel level [about 40 litres left] and fuel sloshing around on 900 km of corrugations and maybe 7 1/2 years dunked in diesel has caused it to pop out and block fuel entry to the swirl pot.
Currently 54-55 litres in the main tank. i need to use another 20-30 litres up to see if it is fixed. I will carry my jerrycan and filter filler until then!

[Doug32 Member Find all posts View Profile Close Doug32]

Thanks to Stevesonly for posting his issue in this forum as there is a lot of good info in this thread to keep for future reference about the diesel fuel system. I also have a simililar problem with my 150_2014 and am replacing the pump and external filter. However, when I pulled apart the plastic swirl pot a rubber 15mm diameter O Ring fell out (see pic). I'm buggered as to where it belongs. Can someone give me a clue? Regards.

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

Summary of this issue with what I have found chasing this around.
Just a quick update on the Prado fuel starvation issue. After lots of searching Pradopoint and elsewhere it was finally sorted 2 weeks ago by replacing the whole fuel swirl pot, sender unit and transfer pump in the main tank. Because of bad design the unit is too big to go through the hole in the floor so 4-5 hours labour to replace the $660 unit..A $1450 job in total at a dealer.
The most common causes are: 1] blocked fuel filter between the 2 tanks. .
2] blocked common breather for the 2 tanks above the diff
3] dud in- tank transfer pump [ now a replace at 7.5 years or 15000km item on post 2018 models]
4] crap in the swirl pot so fuel can only get into it over the top. This happens down to about 45-46 litres ie. 1/4 to 1/3 of a tank with about 250 km remaining
5] there is a 1 cent sized diaphragm at the bottom of the swirl pot. Below the 45-46 litre mark this is what allows fuel into the swirl pot. It is supposed to be inside the pot but mine had popped to the outside so when the engine pump sucks fuel it closes the inlet instead of opening it. Fuel starvation! Google prado 150 fuel sender unit for a picture. There are a few clues that a low fuel level, lots of corrugations at that point and maybe age [mine was 7.5 years old but only 80000 km when it happened]. could be a cause of 5.
A clue to 1 and 2 is difficulty in filling the tanks.
None of the above are an easy roadside fix BUT 10 or 20 litres added WILL mainly go into the main tank. Ignition ON and hand pump until hard. Away you go. Stay above 1/3 of a tank and no issues .I don't know if any of this applies to 200s as well. Hopefully they have a big enough hole in the floor to get the sender unit out! 120 is similar but fuel system slightly different. Ditto petrol cars.
Oh. Number 6 : a random O ring.
Certainly replacing the between tank filter before a trip is a no brainer as is maybe 1 jerry of fuel if going so remote that you may get below 1/4-1/3 of a tank while on rough roads. A scangauge is useful. After 2 fills mine shows 86 l in the main tank and 61 litres in the back tank. I have run it down to about 20 l in the main tank and zero in the back tank so I know the issue is resolved. It shows that the back tank drains into the main tank at about the indicated consumption rate, currently about 11 litres /100km on mine. At about 550 km the back tank is shown as empty. I hope this information is useful for when the oh shit moment happens though realistically with 150000 odd 150s around it really only affects a tiny percentage and the roadside treatment above will get you going.