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.