07 patrol ute zd30crd fuel gauge problem

[robewott]

Going into town yesterday my 3/4's of a tank went down to zero. Low fuel light came on and the sub tank light came on(which it normally does not). I checked underneath for a massive diesel leak but thankfully there was not one.
I can't turn on the sub tank & only the main tank gauge is affected.
Will the problem be around the solenoids or in the cabin?
For some reason the psi on my turbo seems to have got higher(10-13.5 @ 100k/h) I haven't noticed it to be that high before. Would the two be connected in anyway?

[4bye4]

Is the turbo pressure gauge mechanical or electric?

[robewott]

everything is standard

[4bye4]

Can only think if these things all happened at the same time, it could be a loose wire or earth problem. I would guess behind the dash, but thats only a wild guess, may be way off the mark. Check for fuses and loose wires. sorry mate, best I can offer from here. Maybe some others with may have seen this before and will join in. Good luck and have a good Christmas.

[robewott]

I have to remove the tray anyway and weld up the inside of the chassis so i'll start there and work forward.

[Yendor]

Possibly a damaged/cut wire......I would start by checking the main harness for damage, especially where it runs from the rear of the main fuel tank to the chassis.

[the evil twin]

I would be suprised if the boost pressure is related in any way.

The Sub Tank Warning Light will illuminate if there is a problem with the Main Tank Sender Unit "Not Full" test.

You will not be able to transfer fuel from the Sub whilstever that warning lamp is set

The symptoms sound like you have lost power to the Sender Unit.

Check the fuses (not sure which ones as I don't have a manual handy), if they are OK you could try an extra earth but the main tank earthing is normally pretty good.

There is a wiring loom connection on top of the tank that is worth checking as well

[robewott]

after crawling around in the dirt this morning, the problem is in the sender unit itself. There is no continuity through the unit. Both tanks have power to them & the sub tank has 5.4 ohms resistance(it is full). I cant find a unit on Feebay. Does anyone know where i can get a new one online?

[the evil twin]

When I was working on mine about 9 months ago it was 3 choices, New, Wreckers or fix the original.

Try Patrolapart or similar for a price and the wreckers if you don't stumble on one on the 'net

[robewott]

how difficult are they to repair?

[robewott]

patrolapart is closed untill the 5th of January.

[the evil twin]

how difficult are they to repair?

Depends what is wrong.

Mine had two broken wires, one on the outside at the point where they enter the encapsulation and the other on the thermistor on the sender itself .

If it is something like that then a dremel and a soldering iron will fix it but if it is the sender unit windings or whatever then you are better off getting a replacement sender (new, secondhand or wrecker).

[robewott]

The whole float arm had fallen off. I've put it back in & burred it over but i still have no continuity on one wire. So the sub tank light is still on. The gauge works though. I will have to get another one.
It is crap construction. Very light.
I dented the underneath of the rear tank a while back so this was probably an inevitable result..
Thanks for your help. cheers.

[the evil twin]

Which wire and what works now... and did you disconnect the battery?

The only way to reset the Sub Tank Warning is to remove power to the Sub Tank Computer even if you fixed the fault.

On the main tank plug
Pin 1 to Pin 2 - small resistance (sender unit winding for main tank fuel gauge)
Pin 3 to Pin 2 - Open unless Tank is 3/4 full or more (full switch for sub tank computer)
Pin 5 to Pin 2 - Open unless Tank is almost empty (empty switch for low fuel level warning)

[robewott]

black and yellow have continuity, red does not. Both fuel gauges work. The sub tank does not.
I had the battery disconnected for about 5 minutes. The rear tank is about 1/4 . I'll ground those wires. sub full.

[the evil twin]

black and yellow have continuity, red does not. Both fuel gauges work. The sub tank does not.
I had the battery disconnected for about 5 minutes. The rear tank is about 1/4 . I'll ground those wires. sub full.

Bummer...

If you run the Sub Tank self test procedure what fault code does it give you?

[robewott]

The "evil twin"- i don't think so.
It's all sweet. Everything works again, untill the float arm falls off again!!!!
The difference was draining the wires down to a zero value on the volt meter. It was a real "bullshit-no way!!!!" moment.
so sweet to get a win on these complicated cars. cheers:bigthumbup: