VN Wagon running out of petrol on 1/4 tank after fuel pump swap.

[Nzguzzi]

So... I had a small fuel leak from the metal pipe on the fuel pump/sender unit.
Purchased a second hand unit from wreckers.
Side by side, both units are the same length ( wagon units are longer than sedans )
Now the wagon runs out of fuel but the tank still has about 15-20 L of petrol and the fuel gauge reads 1/4 tank.

We have reinstalled the unit again to check everything.
Fuel sender is not bent and seems to be doing its job.
Fuel tank still has enough fuel in it.

Some how, it is like the fuel pump is not getting down into the tank enough for the last 1/4 tank of fuel.
The fuel pump is slotting into its groove in the tank and everything seems to bolt up correctly.
We filled the fuel tank with fuel and the wagon runs sweet.

Totally stumped as to what could be causing this, any ideas?

 

[Nzguzzi]

I figured it may be the fuel gauge itself.
So I swapped back to my old white faced cluster and sure enough, the old dash fuel gauge was reading 1 tick lower than my " second hand restored " dash cluster....

I have taken the black faced " restored" dash apart, but the fuel needle is in the correct position with no way to move the needle any lower to compensate for the difference....

 

[Nzguzzi]

Also, the mechanic removed the fuel pulsator from the fuel pump line. Could this be causing issues when the fuel level gets low?
The pulsator is like a plastic cylinder with 2 rubber grommets that slide over the fuel pipe where it joins onto the fuel pump. The mechanic replaced this with a fuel hose.

 

[Pollushon]

It's tricky but you might need to have a look inside the tank and check the swirl pot is still where it belongs. If it's moved you won't have fuel where it needs to be when the float hits 1/4.

I buggered my pulsator off when I put the Walbro in, I doubt it's that.

 

[IBLOWN]

Assembly is probably bent.

 

[Nzguzzi]

Ok, yes I guess it would only take half an inch to miss the last bit of fuel... ( prob not a bad thing..but annoying )
I think if I have to install it again, I will just bite the bullet and buy a new unit and be careful on next install.
Will check the swirl pot, cheers.

 

[Nzguzzi]

http://forums.justcommodores.com.au...9-fuel-tank-fuel-pump-assembly-swirl-pot.html


Sorted, cheers.

 

[Pollushon]

So, what was the issue?

 

[Nzguzzi]

The wreckers had given me a sender unit from a VR wagon. Side by side, the VN and VR look exactly the same, but when you put them on a bench top, the height is about 20mm different from where the fuel pump pickup sits.
So the VR unit we installed was not reaching down far enough to draw the last 1/4 tank of fuel. Also the fuel sender arm, once the tank was filled, was getting stuck.

Scored another correct sender unit and everything is fine.
Just a pain the first one given to us was incorrect, and very hard to notice the difference between the two units.