Improved sub tank transfer rate.

[Cuppa]

Another little win hard on the heels of my improved fuel consumption.

As long as I’ve had the car the transfer from sub tank to main tank has been quite slow, but I just accepted that this is how it was designed to be. Also whenever I have removed the sub tank filler cap it has always hissed a little, sucking in air.

Yesterday I finally investigated. I tried blowing compressed air through the breather tube into the tank & wasn’t too surprised when it became obvious there was a blockage. Having discovered this I started pulling secions of pipe off one by one, expecting to find a mud wasp nest or similar. The blockage turned out to be right at the end of the pipe right against the spigot on the top of the tank. Unable to push it out I had to cut off the end of the pipe. Finally exposing the cause, it turned out to be one of those little plastic protectors which come on the end of ockie strap hooks! it had a tiny hole in it, which is probably why the tank hadn’t collapsed from a vacuum. How on earth it got there is anyone’s guess! I know when I first looked at the car the sub tank had a leak, & the tank was replaced by the car yard before I bought it.

Now when transferring fuel from sub tank to main tank, the fuel gauge rises probably twice as quickly. :)

[BigRAWesty]

Nice one.
I too have noticed hissing when taking the cap off. I may have a did too see what I can find

[mudski]

Something i have to investigate too. Both my tanks hiss when I open them up. I checked the breather that sits up in the rear guard and it was good. I didn't really go any further with it TBH. So there another small pipe I need to look for....

[threedogs]

Mine does as well I think its normal as my other 4x4 did it as well,
surely not all have a blockage lol
Mine also transfer fuel very quickly.IMO

[clubbyr8]

Both my tanks hiss as well and it seems it takes forever to transfer the fuel, well over 30 minutes....

[jff45]

I was pretty sure mine always hissed when unscrewing the caps so I went out to the shed just now to try it.
My car hasn't been running for 3 days but they both still hissed anyway so I have no idea what it is..

[Robo]

Has someone forgot to remove the protective caps off the tanks before install ??.
Not you cuppa,
But you have given me another thing to look at.
Pat also seems to take 30 mins to take a leak!

[Cuppa]

Has someone forgot to remove the protective caps off the tanks before install ??.


Don’t think so, the replacement tank was removed from another ex Telstra Patrol, besides which the open end of the little cap thingy causing the blockage was faced away from the tank.

[the evil twin]

snip...
it turned out to be one of those little plastic protectors which come on the end of ockie strap hooks! it had a tiny hole in it,


Perhaps some numpty decided that he only wanted a pin hole breather and deliberately put the "bung" in the breather.
They can get a fair bit of pressure differential so maybe the tank breather sucked in the bung till it jammed.
Maybe he was having condensate issues or whatever
It's a longshot but I have seen people do really stupid shit over the years... especially a really ugly bloke I often spot in the mirror

P.S. the factory pump should transfer at 1 & 1/2 LPM.
To work out if the pump etc is OK empty then fill the sub, note the Litres and do the following
Litres added times 1
Divide that by 2 and remember for later
Litres added divided by 10
Multiply by 5 and remember for later
If it is a Diesel set your watch forward 7 minutes unless you disconnect the battery
If it is Petrol leave watch as is but deduct 172 seconds if it is a 4.8
Turn ignition on then off 3 times quickly then once slowly (do not start engine)
Forget what you remembered and if the tank transfers 30 litres in 20 minutes give or take or 70 litres in 45 minutes give or take it is probably OK

[Cuppa]

Do you have a pommy or Scots hetitage ET? Numpty?

[Potsy]

Sorry for the hijack cuppa, but I have a main and sub tank and find that the sub tank leaks into the main even when the switch is not on, not at a great rate but overnight I can see a change on the gauges. Is this by any chance a common issue with the setup.
Mines a 2000 TD42T and I dont get any faults or alarms but am interested to know if this may be due to a faulty pump or maybe a rogue ockie strap protector to!

[jack]

Perhaps some numpty decided that he only wanted a pin hole breather and deliberately put the "bung" in the breather.
They can get a fair bit of pressure differential so maybe the tank breather sucked in the bung till it jammed.
Maybe he was having condensate issues or whatever
It's a longshot but I have seen people do really stupid shit over the years... especially a really ugly bloke I often spot in the mirror

P.S. the factory pump should transfer at 1 & 1/2 LPM.
To work out if the pump etc is OK empty then fill the sub, note the Litres and do the following
Litres added times 1
Divide that by 2 and remember for later
Litres added divided by 10
Multiply by 5 and remember for later
If it is a Diesel set your watch forward 7 minutes unless you disconnect the battery
If it is Petrol leave watch as is but deduct 172 seconds if it is a 4.8
Turn ignition on then off 3 times quickly then once slowly (do not start engine)
Forget what you remembered and if the tank transfers 30 litres in 20 minutes give or take or 70 litres in 45 minutes give or take it is probably OK

Thanks ET, good to see there is at least one other intelligent person on the forum.

[mudski]

Sorry for the hijack cuppa, but I have a main and sub tank and find that the sub tank leaks into the main even when the switch is not on, not at a great rate but overnight I can see a change on the gauges. Is this by any chance a common issue with the setup.
Mines a 2000 TD42T and I dont get any faults or alarms but am interested to know if this may be due to a faulty pump or maybe a rogue ockie strap protector to!
I cant see how thats possible as the outlet for the sub tank transfer is high up in the filler neck. When the transrer pump is on you can see the fuel flow out from the main tanks spout. Unless im missinig something.

Sent from my SM-P600 using Tapatalk

[the evil twin]

What Mudski said... ^^^^
Your sub cannot physically leak or siphon into the main

The sub will, however, transfer fuel into the main as part of the self test every time you start the engine.
This means over time and depending how often you start the engine your sub will decrease in contents but is totally normal for a Patrol

[MudRunnerTD]

Sorry for the hijack cuppa, but I have a main and sub tank and find that the sub tank leaks into the main even when the switch is not on, not at a great rate but overnight I can see a change on the gauges. Is this by any chance a common issue with the setup.
Mines a 2000 TD42T and I dont get any faults or alarms but am interested to know if this may be due to a faulty pump or maybe a rogue ockie strap protector to!

If you have an empty main tank and you go to the bowser to fill up and you take the cap off is there a rush of air? I would check your breathers as mine has suffered from this and was caused suction from the main tank drawing the fuel out of the sub..... Surprising. It should not do this at all though.

[the evil twin]

Do you have a pommy or Scots hetitage ET? Numpty.

Anglo-German... with several documented mental disorders...
Be afraid, be very afraid

[Cuppa]

Thanks ET, good to see there is at least one other intelligent person on the forum.


Who’s the other one?

[threedogs]

so everyone has blocked breather tubes ,, well the majority anyway
I thought it was normal to have a sucking sound when you release the filler cap
especially if near empty

[MudRunnerTD]

so everyone has blocked breather tubes ,, well the majority anyway
I thought it was normal to have a sucking sound when you release the filler cap
especially if near empty

Not sure 3D, i have certainly suffered from this same issue. When i did the Madigan Line i had issues and watched my Sub empty as much as 1/4 of its gauge while driving. at the time i put it down to very rough track and sloshing about as i was crawling in L1. it turned out that when i fitted my Long Range tank i had fitted the one way valve in the breather the wrong way round creating extra vacuum. add to this the split fuel line that happened in the second half of the crossing and my Fuel issues did my head in and i just put both symptoms together but they were not.

[Winnie]

My Patrol does not suck in air when I release the filler cap, my work Hilux with single petrol tank does though.

[Potsy]

I don't think it's the self test as the gauges have changed before I actually start the car. If my main tank is almost empty and the sub half full I can see a drop of around 1/8 of the sub tank in a couple of days (have a work vehicle so Patrice may sit dormant for a couple)
Now you mention it mud runner both tanks make a hiss when the caps are removed but I've never really taken note of whether it's positive pressure or a vacuum, usually to busy staring at my nissanpatrol.com.au sticker.
Please excuse my silly questions but where might I find the breather tubes? Do they come straight off the top of the tanks as I may extend them somewhere a little higher to prevent s#*t getting in.
Will definitely take not of what happens when I remove the caps next time....

[TimE]

Digging up a really old thread but ..............Hiss good, no hiss bad !

My New LRA main tank fitted by TJM Darwin developed a nice leak from the top after I got back home to Canberra. The problem was the way the fuel hoses were fitted, they kinked and rubbed a hole through one line, thus leak. Now the last fill before I noticed the leak I distinctly remember hearing no hiss when I removed the filler cap, thought it strange at the time, I assume that air was entering back into the tank via the holed hose (fuel return hose I assume).

TJM Canberra fixed the problem, no charge, and confirmed that he fuel line had been routed the wrong way, rooted is what I thought.

So, my take away from this is if no hiss maybe an issue with the lines into the tank :(

[4bye4]

TJM Canberra fixed the problem, no charge, and confirmed that he fuel line had been routed the wrong way, rooted is what I thought.
A good bit of PR for them. I often judge companies by how they react when it all goue wrong rather than by their advertised quicker, better, cheaper touts.
Glad they fixed it and you are 100% go again.

[Bigcol]

hiss is good

you have a sealed tank
you have a mechanical pump sucking fuel into engine

open fuel cap - air rushes in

good sign

[Hodge]

Dumb Hodge question time ... But... If there is a hiss when undoing caps , doesn't that mean breather is blocked somewhat ?
If the tank only takes a breath when undoing caps , what purpose does the breather have ?

Both my tanks hiss . When Cuppa originally wrote this thread I was always meaning to check my breather. Forgot about it.

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[mudski]

Dumb Hodge question time ... But... If there is a hiss when undoing caps , doesn't that mean breather is blocked somewhat ?
If the tank only takes a breath when undoing caps , what purpose does the breather have ?

Both my tanks hiss . When Cuppa originally wrote this thread I was always meaning to check my breather. Forgot about it.

Sent from my SM-G900I using Tapatalk

Yeah both mine do too. Both breathers on my tanks are clear though. Im wondering if this is normal as our Commodore does the exact same thing.