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Generation 4-1 Pajero NS Model 2006 - 2009

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Old 12-09-18
erad erad is offline
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Join Date: Mar 2015
Location: Cooma NSW
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If your pre-filter in the tank is choked with gunk, this could cause you problems. The fuel level in the tank is always lower that the main filter, and therefore the main filter is always under slight negative pressure. Negative pressures equals air leaks, equals soft hand primer pump. Since someone obviously has had your Pajero fuel system apart, this is a good place to start looking.

I fitted a pre-filter to my NW Pajero, and the filter mount leaked air. I tried double clamps on the rubber to steel fittings, but no difference - it still leaked air. Eventually I took it to a mechanic and he removed the pre-filter and tested it with a vacuum pump. Bingo - it leaked. He put a new gasket/washer in the top if the filter body (where a hand pump would normally go, it was blanked off with a plug and that plug was leaking. Eventually he reduced the air leaks, but could not eliminate them. He got to about 20 inches of mercury. but could not make it tight beyond that level of vacuum. I reasoned that at most the difference between the bottom of the fuel tank and the pre-filter was about 500 mm, which would equate to about 1.5 inches of mercury. so that was well within normal operating range. I never had any problems after that event.

So if your pre-filter in the tank is choked, it could cause losses such that air will get sucked in. The possible symptoms of this problem could be that the engine will run but not go very fast. At slow engine speeds (eg idle) the main fuel pump will suck fuel into the common rail as fast as it can, but because you have low engine speed, it won't be pulling that much fuel from the tank. What fuel is not needed for the engine is returned to the tank. As you increase engine speed, the main fuel pump will pull more fuel from the tank, causing more losses at the in-tank filter, and if you have an air leak, it will not like it and the engine will stop Since someone has been paddling around with your fuel system, it is possible that they may have induced an air leak somewhere in the system. And as your fuel level goes down, you get more negative pressures (more air leaks).
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Old 14-09-18
Piet Potjie Piet Potjie is offline
Join Date: May 2016
Location: Pretoria SA
Posts: 64

I opened my fuel pick up up as a preventative measure. Found a post where some one found the valve contraption in the white plastic housing had fallen apart. Mine had also fallen apart. Not a very well made item / cheap. Some contention as to what exactly this valve is supposed to be for. My thoughts are it directs the draw of fuel from a higher level / away from the bottom of the tank and only once the level drops, allows fuel to be drawn from the lowest level. Either way this could cause a problem as it is not well made. I like the other poster decided to opt for reliability rather and disconnected it and my tank draws from the bottom.
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Old 14-09-18
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kiwi1973 kiwi1973 is offline
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Join Date: Sep 2012
Location: New Zealand
Posts: 1,067
Default Update

Thanks for all the assistance and ideas. I could so easily have wasted a whole day following my initially intended hierarchy of diagnosis, which I set out in the first post, and none of it would have worked given there was no fault and the car had simply run out of diesel (I went for a good drive today and all is well).

Today I filled up with diesel to the very brim to see how much it would take. It took 81 litres and there would have been about 5 litres in there from the jerry can. There is something not quite right with this. I should have been able to add about 84 litres (i.e. 83 litres would get to the 88 litre limit of the tank + say 1 litre to fill to the 'brim').

I phoned the fuel injection firm to discuss and they asked if I'd hit anything on the bottom and dented the fuel tank..... this reminded me that indeed we did in July. A non serious rock impact to the fuel tank, but nonetheless enough to put a small dent in it. I didn't think too much of it at the time.

So the issues with the car now able to run out of fuel despite the fuel level not all out and fuel light not 'on' could be due to the dent in the tank as opposed to something done by the fuel injection specialists in March. It doesn't look like a 3 litre dent, so I'm not fully subscribed to this conclusion just yet. I guess I need to remove the plastic protector and get a better look at the dent.

How to remove a dent from a fuel tank? To any of you who have opened the top of your tanks would it be possible to access from there - bit of wood and hammer perhaps? Alternatively I have a spot welder specifically for use in repairing dents in automotive sheet metal. You just instantly spot weld to the metal and then are able to pull dents out. I'm not sure what the thickness of the fuel tank is and whether this would likely work.

An important point of note though is that this wasn't actually a breakdown - just out of fuel.
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Old 14-09-18
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KiwiNTPajero KiwiNTPajero is offline
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paintless dent removal outfit?
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Old 14-09-18
NJV6 NJV6 is offline
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What sort of dent is it do you know? If it doesn’t have a crease in it then compressed air works well.
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Old 14-09-18
Seigried Seigried is offline
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You could try it this way. Pics in link

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Old 15-09-18
Garc Garc is offline
Join Date: May 2015
Location: Perth
Posts: 121

I have the OEM fuel tank from when I replaced it with the ARB bigger one.
There are a lot of internal horizontal baffles inside the tank, big flat plates. I think it would be difficult to bash out from the inside unless you are very lucky to have the dent in a hole in the baffle.

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