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TOPIC: Fuel pump 1989 S4

Fuel pump 1989 S4 03 Nov 2018 22:42 #20652


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  • Jjburns15
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My 1989 S4 external fuel pump sounds as if it is running and fuel goes in on the left side but none comes out on the right exit to the filter side.
The car was sitting in the garage for 10 years without being run and I am trying to get it back on the road.
I was told that if I hear the pump running that it is pumping fuel ! Is that true or can a pump run but not pump fuel ?
Thank you all for your assistance !
Great idea for a 928 club!
Best,
John
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Fuel pump 1989 S4 07 Nov 2018 10:53 #20655


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If there is fuel coming in from the tank side and no fuel going out of the pump side then clearly there is a blockage within the fuel line or pump. It could be that the pump motor is running but the pump section isn't turning. I suggest removing the fuel pump and inspecting it.

Please be aware that there is an in-tank screen to filter fuel before entry to the fuel pump. Particles can block the pump, some say that briefly applying reverse polarity to the pump electric connectors will reverse the motor rotation and possible clear out obstructions. I've never tried this process.

FuelStrainer.jpg


As the photo illustrates, as the screen ages it may detach from the housing and large foreign particles from the tank can then be sucked into the fuel line. So I suggest replacing this in-tank filter. It is part number 928-201081--04.

If you Porsche 928 has an in-tank pump, that pump also has a screen that can detach. So inspection of the in-tank pump is also recommended. Replacement in-tank pumps are quite expensive, I hope the prices decrease in the future.

Care must be taken when removing the in-tank screen or fuel pump as the metal threaded portion in the tank is set into plastic. If the metal to plastic seal is broken a replacement tank may be necessary, and AFAIK, there are no new fuel tanks available (except one at my mechanic's shop - Exotic Motorwerks in Arizona).
Rich
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