968 Fuel pump starvation

I am rapidly learning about the fuel pump in a 968, mine has failed twice due to a fault in the tank that causes fuel surge.

Now, having dismantled the last failed pump some useful observations emerge:

1. All the motor, wound armature, brushes etc are immersed in fuel -- that surprised me -- put it down to over exposure to older style SU pumps.
2. The pumping action comes from a very small metal vane type armature that runs in an off centre chamber -- the vanes are in fact small metal rollers that are forced out to the chamber walls by the high speed rotation of the pump.
3. I conclude that the pump must be full of fuel if it is to operate correctly, so you cannot bench test it unless it is full of fuel.
4. I advise all 968 owners to never allow their car to run out of fuel -- the risk of fuel pump failure is very real, even though the DME controller would shut the power to the pump if the engine stopped turning. It may be too late to prevent damage -- I suspect that if you run the pump dry say 5 or more times, even for only a second or two each time, then the risk of seizure becomes very high.
5. I am puzzled that the replaceable fuel filter on our cars is after this pump, the chambers in the fuel pump are so small that the risk of some foreign object jamming the pump seems significant.
6. I am told that there is also a fixed filter in the bottom of the tank before the fuel pump -- I will try and confirm this soon.
7. The pump is made by Bosch, it cost me £79 + VAT, I got it from Euro-Car Parts, it does only take about 20 minutes to fit.
8. If you do have the 'known' 968 swell pot problem in your tank and fuel surge occurs during sharp right handers when driven hard -- then you would be advised to buy a spare pump and keep it in the car!

if this info actually helps someone else -- it will be a blooming miracle!!

Paul Follett,

968UK veteran.

 
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