Alright so recently my mate and i attempted to fix this common issue of our fuel gauge showing the incorrect fuel level. Usually when you'd fill the tank to the top the needle will only go 3/4 of the way and you will find the needle also showing empty within a few hundred km's..
I'm briefly going to explain how to fix this issue - we did this yesterday morning and unfortunately did not take any pictures so i'm going to use a few pics that i found on the internet that are all still very relevant. Let's get started then -

What you'll need:
1. Pliers (these are used to turn the 4 black clips that hold down the cap)
2. A few rags or a towel to clean up some spillage
3. Screw driver to remove the 6 screws that hold down the lid to the tank
4. 10 or so Q-tips (we call them ear buds)

Estimated Completion time - 1 HR to 1.5 HR. Took us almost 2 hours only because it took AGES to work out how to lift the seats up haha!

Again i just want to say sorry for not getting any pictures.. i will try to explain it as easy as i can without them.

Lets' get started then.

Now, the trick to lifting the back seats is simple. All you need to do is pull hard in the middle of each seat at the front. Don't worry you won't break it, there is a latch on each seat. Once you've got them up the seat should sit up by itself - if not use a bit of wood or something to keep it from dropping.

Next, your going to want to do the drivers side unit. In my case, the drivers side one has the fuel pump in it so it should be opposite for you (assuming it's a LHD V35) since my car is RHD. We opened the side with the fuel pump and couldn't actually find the unit since it's all hidden by a pink capsule sort of thing because of the fuel pump so we went and did the other side instead.

Next, you will see where the tank is accessed on both sides. There is a plug leading into it with 4 black tabs. It's easier to use pliers here than a screw driver - we found ourselves stripping the tabs with the screwdriver since it's plastic so pliers was the next best thing to use.

Once the tabs line up lift up the unit - You then should see the lid that leads directly into the fuel tank. There will be 6 bolts holding it down, and 2 plugs leading into it. Disconnect the white plug on the left of this picture first and let the first lid hang down.



This is the part where you need to get your towel/rags ready. The black plug that connects in the middle is directly linked to the fuel tank. Because the line is pressurized (if you have been driving recently) when you disconnect it, it will spit some fuel out. I will also recommend that you run the tank as low as you can before doing this - If the tank is full it will spit A LOT of fuel out..

As per the above picture the yellow arrows indicate you need to hold the blue tabs away from each other while pulling the black plug (the tabs are actually white but doesn't matter). Then remove the 6 bolts that hold the lid down, be sure not to loose these as they are quite small. Once you have pulled up the lid you will see the fuel sending unit, it has a floatation device at the end of it so you need to maneuver it a bit to get it out..

Next, time to clean the unit. In the below picture, you will see a sort of circuit board looking print on the unit. (There is actually a bit of plastic in front of it, but if you turn it on the side you can see the black board, you can remove the plastic in front but it doesn't matter you can still clean the unit very well with it on).



What you need to do here is grab a Q tip and start rubbing it on the surface. I did it in a circular motion. Once you've been rubbing for a minute pull it out and see how much crap is on it (mine wasn't too bad, but it was noticeable..) continue doing this until you've gone through about 5 q tips or no more dirt rubs off..

That's it! You're done. Now what you need to do is put everything back together and go fill up, should also mention that your car is going to smell like fuel for a bit lol.. but it will go away.

One last thing - If you fill up and your gauge DOESN'T look like this..

It can be either 1 of 2 things.
1. The sending unit on the passenger side is dirty (this one has the fuel pump connected to it)
2. Your sending unit is ****ed.

I think that's it.. sorry that it's not perfect, this is the first time i've written one of these i've had lots of requests to do it so here it is.. It worked for me, it should work for you too!

 

yea buddy!

 

could a moderator please move this to the DIY section? i couldn't post there. cheers

 

Glad I came across this. I have this problem. From my right understanding, our cars have 2 sending units?

 

Hey guys i am a new face to the group but i have been told the hardest part of fixing the fuel gauge on my GT 350 V35 coupe is getting the bloody back seat out can anyone confirm for me please as i am going to attempt to clean the fuel pump and sensors in the next few days cheers guys

 

No that's definitely the EASIEST part, reach under the seat and feel around for the two rings that hold the seat in place, pull on them and the seat pops right out. Take me all of about 5 seconds to do it.

You should definitely check resistance on the harnesses first before you go opening up the pump/sub. You can verify it's either working or NOT working by reading the resistance of the sending units from the harness without taking them out. Just be sure to get the vehicle to a point where you know the gauge is not displaying the correct fuel level then check the pump/sender.