Cayenne 2005 fuel pumps operation

[makoco]

Among my cars I own a Porsche cayenne base (955 2005 v-6). I left this vehicle parked for 5 years with no use it has 6000 miles

I tried staring it and cranked on the first try, run for apron 5 seconds ( while run only by the fuel in the rack ). Both pumps fuses where shorted ( apparently as the raise in amp by the pumps being locked)

Replace the fuses and check the relays and the engine never started.

Replaced both pumps, the fuel filter, pressure regulator and fuel level sending units. The Cayenne worked fine until it reached approximately half tank. It turn off as it did not had any fuel. Fill up the tank and work perfectly again. Same situation happened again when it reach half level.

The sending units and gauge are giving correct readings. Leading to the understanding that one of the pumps is not transferring the fuel to the pressurized side.

The mechanic is insisting that the issue is from a damaged DME. I contacted several electronic shops that service (repair) damaged electronics and all mentioned that its strange and that never have found this condition from a bad DME board. When feeding (electrically) the pump that does not turn on from the other electric feeder it turns on ( meaning that the pump is in working order)

Whats your opinion related to this issue. I don’t fully understand how the logic of the pump operation in this vehicle

Any advise will be appreciated

Marcos Rodriguez

[fintstone]

I would suspect that your float is catching on one of the cables at about the half full mark and your tank is actually empty. I have seen this before...after the pump replacement was done by an Indy Porsche mechanic. They were certain that there was a pr0blem with my gauges...so I opened it up and fixed it myself. I just moved the cable and tied it up. Fill it up (when half full) and see how many gallons it takes. Compare that to your tank capacity (if you have not already done this).

[Tonod]

Definitely not a dme,something is wrong in the tank.one side is empty,just have to go back in there and figure out why.there should be plenty of diagrams available on google of hoe it is supposed to be set up.hose not secured properly,pickup jet not sitting properly,who knows when humans have been there.has the mechanic gone back in there and re-examine the layout,he should
https://cimg9.ibsrv.net/gimg/rennlist.com-vbulletin/1300x632/porsche_cayenne_touareg_fuel_pump_hoses_diagram_8a eea8c6e97563e86793961ff44452f5f22709d7.jpg

This is a set up I found on google,might help

[Tonod]

One more thing,if he says a bad dme that would suggest a pump not operating but if on full tank car operates properly what is dme doing wrong to cause this.one pump not workin would cause a fuel starvation problem that would show up at any fuel level.this is just common sense and sounds like he is overwhelmed by the intricacies of the fuel system which is relatively simple by today’s standards

[island911]

Know that there are 2 level sensors (one for each side) and the system is designed to move fuel from one side to the other.

I was replacing a driver's side pump today. Fuel level was very low Left and High on the Right. This was after I was running on only the right pump for a while (primary/Left pump fuse pulled)