Fuel System Overhaul

Bert87 · Bert87's Garage

Typically I like to figure this kinda thing out on my own as I know it is a bit of guesswork without being able to look at the actual car, but the car is 6 hours away and I have limited time to work on it. I am looking to overhaul the fuel system from the tank to filter. The car is a '71 911T with a '88 3.2. It runs great with no leaks however I have a replacement tank, would like to replace the old noisy pump, and relocate the pump from the rear to the front near the tank.

Current routing is as follows:

'71 tank -> 10mm hose -> 10mm metal tunnel line -> 10mm hose -> old bosch pump -> ~5/16in hose -> ~5/16in hard line -> 5/16in hose -> fuel filter

Proposed routing:

SC tank -> ??in hose -> in line fuel pump (Bosch BOSCH 69458) -> AN-6 hose -> ?? metal tunnel line -> AN-6 hose -> 3/8? hard line-> AN-6 hose -> fuel filter

So the questions are:

SC tank outlet size (looks like the pump inlet is 1/2in) and inlet threads?

Best to use a metric banjo to AN from the pump outlet or is there a better option?

Should I replace the hard line that runs from the drivers side wheel area into the engine bay with 3/8in to keep it consistent (currently roughly 5/16in)?

Fuel filter ('88 3.2 filter PN 928-110-253-06-M67) inlet threads so I can replace the current adapter with one to fit the AN fitting.

Applying fittings to the body lines. Is it possible to replace the hard lines from the front with the tank, steering rack, etc removed? Would be much easier for me to use 3/8in tube and would know exactly what I have. My preferred option is replacing both supply/return with 3/8in tube with AN flared fittings.

SalParadise · 05-17-2018, 12:37 PM

Bert -

This is going to be a big job.

Is the engine in the car? If it is, don't attempt to do this tunnel lines. You will lose your mind. The lines have to go from front to rear. You will have to do the tunnel lines no matter what. Porsche sells the 10mm polymid line that goes through the tunnel and has the flexible end and connects directly to the SC tank in front. You can buy that official Porsche part here. In using this line you will have to drill so a larger grommet will fit the tunnel on both ends.

Your best bet here is contacting Len Cummings (aka BoxsterGT). Len is the go-to man and has decades of knowledge on how to connect the SC tank to the 3.2 motor through the 1971 tunnel.

Trust me - you will need Len Cummings to do this correctly and he will be the man to go to. You will lose your mind without specialized knowledge in this area. It was hard enough for me to convert the newer lines from a SC tank to the original engine in my car -'75 S. Not all these lines are available from Porsche to do your conversion correctly.

Mark Salvetti · 05-17-2018, 04:03 PM

So it sounds like you are currently using the metal tunnel lines that came with the 1971 body, but you want to switch to new flexible lines?

I agree that BoxsterGT is the way to go. The Porsche SC tunnel lines are one-piece to the fuel pump and for the return to the tank. Len makes replacement lines that are multiple segments, which I think will be an advantage for you since you are sort of cobbling together a hybrid system.

One challenge you may have is threading the new lines through the tunnel. If you were replacing existing lines you would use the old ones to pull the new lines through. You can’t do that, but I’m sure there must be a trick to it.

Mark

SalParadise · 05-18-2018, 04:22 AM

Quote:

Originally Posted by Mark Salvetti

One challenge you may have is threading the new lines through the tunnel. If you were replacing existing lines you would use the old ones to pull the new lines through. You can’t do that, but I’m sure there must be a trick to it.

Mark

The trick is putting weed eater line or cable through the existing lines - remove the existing lines and leave the weed eater lines in there and then you at least have a guide to bring the new ones through.