Don't blame the sender - Part II

Southernboy

Zorg Guru (II)
3rd Party Trader
Joined
Apr 27, 2012
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Some while ago I posted a thread " Don't blame the sender" in which I described the fixing of the problem of a sticking or non operational fuel gauge.
In that article I described how to operate the float arm with the pump / sender assembly in position in the tank. This was a fairly complicated process and was only 50% accurate, since the float arm could not be manipulated all the way through it's possible arc.
Since then, I have had a broken ceramic card and replaced it with a new one. In doing so, I had time whilst waiting for delivery from Europe, to re-think the problem. Firstly why the original card had been cracked and secondly the issue of free float arm movement.
Starting with the second issue - The absolute simple and best way to operate the arm with the pump assembly in position is to use some fishing line which is passed through a short ( 300mm) piece of 10mm plastic tube. This plastic tube will hold the filler tunnel spring cap open whilst allowing the fishing line uninterrupted movement. On the inner side of the pipe, tie a long ( + 200mm) cable tie. this will drop down into the filler tube until it hits a 2nd little trap door which can be accessed through the opening in the tank with the pump assembly removed. Once pulled through you can detach the cable tie and tie the line to the float arm just above the float and onto the wire arm.
This will allow full lift and drop of the float arm with the pump fitted into position. Obviously it must seat into the tank fully and correctly aligned with the marks on pump and tank.
Now to the reason for the broken ceramic card - The float arm has a slightly conical shaped pivot which over time wears thinner as does the tube into which it fits. - these are all plastic parts.
I happened to open a new can of Milo and the aluminium seal under the plastic cap got my attention. It is quite thick and sturdy material. I kept it anticipating the task coming up. I used it to make a 360 "bush" around the pivot shaft - carefully so there was no overlap at the ends.
The consequence of the worn shaft and hole, is that the arm can move extensively back and forth with the splashing about of the fuel under braking and acceleration. The ceramic card can thus bump into the main body of the pump against the 2 wired contacts and force them inwards to the extent of their springs. When that point is reached, the card is under pressure and can / will be broken.
So, with the bush in place, using the aluminium seal, the amount of movement is almost zero from front to back.
This means the card cannot be forced into a pressured position and possibly crack / break,
Finally, where does the float arm stick - This can only be on the forward side of the tank - closest to the steering wheel, or on the opposite face furthest away from the S/Wheel.
I my instance, I discovered it was catching on the rearward face, and with a slight amount of bend to the float arm and then testing using the fishing line procedure above, I managed to get a full lift and free falling drop without any contact with the inside of the tank. Obviously, it's a bit of a trial and error thing - too much bend and you have the opposite wall catching etc etc... little by little will get you there.
Once you have found this sweet spot, simply cut the fishing line away and fit everything together.
If you're going to do this job yourself - it may seem convenient to use a hammer and a screw driver to loosen and tighten the pump assembly securing ring - my advice is don't. In both instances, there is no fuel to cushion the blows and possible subsequent movement of the float arm - this may result in breaking the ceramic card. I made a simple tool which you can see and refer to in the Z3 roadster and Coupe forum under the title "A new Tool" It is easily fabricated and will provide proper and careful removal and replacement of the securing ring.
It goes without saying, before you can do anything in the above task, you have to drain the tank or face fuel pouring into the car when you remove the pump assembly...
 
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