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Sub fuel tank not working

Rambodian

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Joined
May 30, 2017
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23
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australia
Hey guys,
Well today I took my 2002 HZJ79r LC for a good 4wd day trip, and before we left I filled both my diesel tanks.
Mine has factory fitted individual 90ltr tanks, both have their own filler necks. One under the rear tray, the main in the regular spot.
I can't find much on the internet about it, so I thought I'd post it on here and see if you guys can steer me on what to do.
My rig has 2 seperate fuel guages in the instrument cluster, and to activate the SUB fuel tank you just press a button which is located kinda down near the low range shifter but on the console. A light on the dash board turns on and it simply says "SUB" to indicate your using the SUB fuel tank.
Everything works, (or worked until today) the SUB light turns on when I press the SUB button etc. I soon realised that my SUB tank was indicating that it was "on" but the fuel guages were indicating that the main tank was the one being used.
What could stop it working?
I did just have the clutch replaced, but when I climb under the vehicle nothing is unplugged or looks out of place.
I read somewhere on the net that undoing the battery for 30min can fix it so I tried that. It didn't work for me, my SUB is still indicating that I have it on but fuel is being used from the main tank instead.
 
Darn no replies
Oh well I give up lol
I've booked it into a diesel specialist for Wednesday morning. I'll check back in with the fix so that there is at least something out there about it.
 
There is a 4-ways valve, solenoid activated. You'll see it under the car, if you follow the fuel lines from the engine to the tank. That's the culprit, 99%. Either it's frozen, or the wiring is cut/broken/disconnected.
 
There is a 4-ways valve, solenoid activated. You'll see it under the car, if you follow the fuel lines from the engine to the tank. That's the culprit, 99%. Either it's frozen, or the wiring is cut/broken/disconnected.
Thanks heaps for the reply mate, I work 12 to 14 hour shifts so I haven't been on in a few days. I've got tomorrow off work so I'll jump under and check it out.
 
Well I found the culprit, a wire that was broken inside the protective conduit just before the solenoid. Explains why I couldn't get the darn SUB tank to work.
Trouble is, there was no marks on the conduit to see damage. The only thing I can think of is the conduit got caught when the mechanics pulled the gearbox out for the heavy duty clutch I guess. Maybe it stretched the wire inside to breaking point.
In any case, I soldered it up, sealed it and put it all up as high as I can get it.
All fixed
 
Rambodian, hi. I am having the same problem.
There is a 4-ways valve, solenoid activated. You'll see it under the car, if you follow the fuel lines from the engine to the tank. That's the culprit, 99%. Either it's frozen, or the wiring is cut/broken/disconnected.
Thank you. I have the same problem. Will try what you said.

Well I found the culprit, a wire that was broken inside the protective conduit just before the solenoid. Explains why I couldn't get the darn SUB tank to work.
Trouble is, there was no marks on the conduit to see damage. The only thing I can think of is the conduit got caught when the mechanics pulled the gearbox out for the heavy duty clutch I guess. Maybe it stretched the wire inside to breaking point.
In any case, I soldered it up, sealed it and put it all up as high as I can get it.
All fixed
 
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Hi, I drive a Landcruiser Prado VX 2001. Anyone have any idea why recently when clicking my sub tank the fuel seems to be then transferring into the main tank? Whereas before the fuel gauge on the sub tank would go down as fuel was used.
 
Quite informative, thanks to all! Do have the tanks, don't have the poblem, but I'm sure someday this will come in handy.
 
Hi, I drive a Landcruiser Prado VX 2001. Anyone have any idea why recently when clicking my sub tank the fuel seems to be then transferring into the main tank? Whereas before the fuel gauge on the sub tank would go down as fuel was used.
This is a common issue on the 70 Series so guess the 90 may be the same.
Basically the changeover solenoid for the fuel involves two Valves a Supply and Return - when one of them fails you end up with a fuel transfer situation such as you are having. problem often is you end up overfilling one tank if already full.

So the fix is to isolate the issue either wiring or mechanical - either replace the valve or fix.
No idea if they are the same valves but I do know they are both available and expensive!
I replaced mine with an aftermarket 3 way valve but buy the time I purchased all of the correct size hose fittings I doubt it was much cheaper.
 
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