Fuel return lines 71T?

[zithlord]

I noticed while removing the US emission system on my 71T that there is no return fuel line from the engine back to the fuel tank. Is this correct for a original Zenith carbutated 71T fuel setup?

I found this on Pelican:

An originally carbureted car doesn't have the return lines, it's really pretty basic.

Anyone have a good drawing/diagram showing the fuel lines/setup?


John

[TargaFlorio]

Yes, Zeniths do not have a return fuel line.

Some 911Ts that were delivered to hot climate areas were fitted with an additional circuit to help fuel vapors to escape.

Both Weber and Zenith carbs don't need the return fuel line since the fuel pump is generally a low pressure affair (compaired to the fuel pump for a MFI car)

Cheers,
n.

__
http://nicolashunziker.com

[project 911]

That's correct. Just a return (or bypass) line from the pump back to the tank. So, two lines between the pump and tank, and just one to the engine.

[Scooter]

My 70T with Zeniths came with the return lines, but I just removed them, because they are unncecessary.

[Todd Simpson]

My '71T has return lines as well. When I did a 2.2S MFI swap everything went right in.

[Grady Clay]

John,

Here is a good thread on this subject with lots of links: ”Weber fuel recirculation- Questions“

Your T should have the return line in the chassis and used to return the relief from the rear mounted pump back to the tank. All it takes is to plumb the best circuit. It is very desirable to locate the pump in front (as with ‘70T) and insulate the hoses in the transmission and engine area.

You will notice in the above thread that we (Pelicans collectively) came up with the best circuit that passes cool fuel past the carb inlets and has a pressure regulating return to the tank.

Your ’71T should already have the phenolic insulating spacers between the heads and intake manifold.

Best,
Grady

[zithlord]

Hi Grady

My model year 71 has the fuel pump in the front(just behind the fueltank), like the 70. Its produced late 1970. I guess it then should not have the fuel return line from the engine through the chassis to the tank. Its seems the transition from front pump to rear pump must have been in the middle of the modell yar 1971?

John

[Grady Clay]

John,

I’m pretty sure you have the return fuel pipe in your chassis. It should have a rubber cap on each end. Go look.

For my records, what is the last four digits of your VIN? Porsche claimed the change was with the MY ’71 but I too have seen early ’71 MY with the pump in the front.

I’m pretty sure all 911Ts MY ’69-’70 have the MFI return pipe in the tunnel. Porsche didn’t distinguish it was going to be a T, E or S until later in the manufacturing process. (The Sportomatics even have the clutch cable tube in the tunnel because of this.)

Karmann produced some 911Es in ’69-’70 (not ’71 and no 911S) and they too have the return pipe in the chassis as Porsche could assemble them as either an E or T.

My SWB didn’t come with a return pipe (none did as far as I can tell). I installed one alongside the tunnel on the passenger side.

Best,
Grady

[zithlord]

Grady; my car has VIN number 9111120638. I have checked in the rear and there is no bracket for the fuelpump like the one in the rear of my 73(MFI). I might have overlooked the capped pipe, but I am preatty sure there is just on fuel hose coming from the centretunnel pipe, its going op to a new pipe that runs under the backseat and along the inner quarter and then into the engine compartment, where a hose is attached to the pipe and runs to the carbs, I can see no hose or pipe going the other way.

John

[zithlord]

BTW I had read the link you referred to when I searched for the answer to this thread. I could not find a good answer to my spesific question when I searched this forums old treads..

But with your help everything is possible, I have seen from old treads and later posts that you help out a lot of people, and you should have been given a medal for it.

Thanks
John

[Grady Clay]

John,

Your ’73 will have two different size pipes in the tunnel. The larger one is the supply to the rear pump and the smaller is the return to the drain fitting in the tank. The ’71 should have two the same size for the standard 7 mm hose (999.180.030.50) and the 12 mm Norma Schellen (N-S) clamps (999.512.174.02).

I’m in favor of having the hoses continuous from the pipes at the tunnel to the first connection in the engine compartment. Most leaks are at connections and fittings. If you minimize the number of connections, you reduce the leak potential. The reason for the insulation on the hoses is they pass close to the heater waste hot air at the heater control valves. I prefer to route the two insulated hoses between the rear shock cross member and the firewall. There is a foam insulator there so it is easy to push aside for the hoses.

Flattery goes a long way but even without this it is worthwhile to keep my brain functioning.

Best,
Grady