el jefe

Here's where I decided to start, at the back end of things. The fact that she could not hold idle and die with the blip of the throttle led me to believe that A; we had a fuel delivery problem, B; we had a vacuum problem or C; a bit of both. My aim was to drop the tank and start the diagnosis from there. 
Beginning with the fuel pump, I loosened the two 10mm nuts hold the carrier up against the tank. When I dropped it, the fuel pump was just floating in there not anchored to anything. No wonder that the two additional nuts under the carrier were mysteriously loose. The studs on the fuel pump cradle (bottom of image) had separated themselves from the rubber bushings meant to suspend the fuel pump itself and minimize noise as well as protecting it from external vibrations. Then I noticed to additional wires that you can see off the fuel pump wires taped up...not good. At this point I decided to empty the remaining fuel fuel from the tank so that I could investigate further.
It has been relayed to me that the fuel pump was new...clearly this doesn't look new but it new could also be "new" in the secondhand sense, I dunno. It works so it stays. The extra wires have me puzzled though, was it to power a second fuel pump?

Below is the fuel pump cradle with the rubber mounts clearly detached from the studs under it.
While draining the gas from the tank, I figured out where those two mystery wires belonged...to the second in-tank fuel pump which was disconnected. I was under the impression that the second fuel pump lived up by the fuel expansion tank/filler neck. Clearly the work of an amateur here.
Moving up to the fuel level sending unit it looks like the plug was either spliced in or the wires chafed. It should have been done using shrink-tubing though. Notice the return line above, frayed and most definitely the original, it must be replaced. The trick with this guy is that he is attached to a hard line under the body using the factory rubber-to-hard line crimped connection. I'll have to cut this connection off and clamp a new section of fuel line in. Most of these fuel lines are no longer available so they must be rebuilt using this method.
Now I was ready to remove the fuel tank. First I fished out the fuel filler neck grommet (totally deteriorated) to expose the hex head bolt holding the neck. You can see in this image the two fuel tank vent lines, the one on the right goes to the expansion tank while the left goes to the top of the fuel tank. I would strongly recommend cutting the left hose at this end since it goes through the frame to the top of the tank making removal impossible. You don't want to pull it off the T-fitting because you can snap it off, cut and replace is the way to go. The right side hose was pulled off the expansion tank side, if anything I'd rather risk breaking off that nipple fitting than the one on the tank, a used tank from Parts Heaven hovers around $400 plus shipping.
What was left of the fuel filler neck grommet, well it is 34 years old after all. Mike Liptak, my Porsche parts expert at Ray Catena Porsche in NJ tells me this guy is still available (part # 928 201 333 02) for around $60, be sure to also order the drain bush (928 201 255 02) and the outer ring that holds the grommet in place (900 906 046 00). If you are close to this dealer in Edison NJ, be sure to ask for Mike...he's a pleasant guy and knows his Porsche parts.
There she is, the old "ostrich" so called because it looks like a headless, legless ostrich. All it took was the removal of four bolts on the frame to release the tank cradle and then the tank is free. You'll need to wiggle it out a bit as the fit is slightly awkward. I found that lowering the left side first and then massaging out the neck worked. You'll figure out how once you get into it.
The mystery of the two dangling wires off the fuel pump solved, here is the elusive in-tank fuel pump that they connect to...why it was disconnected is still a mystery though. 
Here's a close up of the fuel hose connected to it. Could be the original and despite the cracks, it surprisingly didn't leak. Still available from Porsche part # 928 356 550 04 but at a price of around $45. Have yet to find it from anywhere else and since the hose is moulded, you kinda have to use an OE part.
The view from where the tank came from looking aft...yep, she was never hit from back here. A testament to Porsche's high build quality and craftsmanship, no corrosion. Unbelievable for a 34 year old car.
Another view looking towards the driver's side. You can just see the gearbox on the lower right of this image and one of the screws that holds the tank in place.
And the view from the passenger side looking out of the fuel filler hole. No evidence of body work here. Lookin' good so far.



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