Fuel return line??

Allenk · 07-13-2002, 03:14 AM

I have a 71' 911t That by looking a a fuel diagram, seems to have the fuel return line blocked off at the engine compartment. Do I need this. I can't find where it goes and I'll stop trying if I don't need it.

Roland Kunz · 07-14-2002, 02:17 PM

Hello

71 2,2 T should have a front mountet fuel pump and no need for the returnline.

You only have one fuelline coming up into the enginebay and thats it.

Grüsse

Paul Thomas · 07-14-2002, 02:48 PM

It is there for the MFI cars

Paul

Allenk · 07-14-2002, 06:08 PM

Is this true for all carb set ups? I have the Zenith TIN40 carbs and the rebuild guide mention these as a continous feed system.

Fishcop · Fishcop's Garage

I think the continuous feed is internal within the Zenith carbs, there is only one line supplying the fuel. Once it gets to the Zeniths, it is recirculated within the carb unit.

Roland???!!!

T Bird · 07:41 AM

Allen
Isn't your fuel pump mounted at the rear of the car, near the driver's side control arm?

No matter. The OEM Bosch fuel pump for your car has a return line fitting. In fact it has 3 fittings: D= delivery to carbs; S= suction from gas tank; and R= return to fuel tank. The return feature is critical. As I explained in my earlier post to you, when presure in the delivery line to the carbs reaches a prescribed cutoff (2.8-4.2 lbs.), the return line is activated and the excess fuel pressure is bled off by redirecting the fuel back to the tank. This is how the pump maintains relatively constant fuel pressure, and this is what keeps your needle valves from being overwhelmed.

Check your pump. It should be 911.608.107.00-- a Bosch roller cell fuel pump.

Good luck.

Allenk · 07-15-2002, 04:53 AM

Well I know I don't have that set up. One line in, one line out, seems like a problem. My fuel pump is located under the car in a little metal saddle by the drivers side torsion tube. Was it relocated to this position from the engine compartment thus explaining the return feed line that goes thru the fire wall?

T Bird · 07-15-2002, 06:12 AM

The location is correct for your car. The question is, what kind of fuel pump is located in the "saddle?" Is it OEM with 3 nipples, or something else?

Allenk · 07-15-2002, 08:12 AM

It's not a 3 nipple pump. It looks like when the pump was replaced, one specified for Webers was used. Seems a waste-their not cheap.

T Bird · 07-16-2002, 03:54 AM

Allen
You have some options. You can replace the existing pump with the Bosch pump mentioned above. The advantages are that it is the correct pump for your car, fits in the prescribed place, and provides correct fuel pressure. The disadvantages are that it is expensive and getting harder to find. Another option is to use what you have, but to add a pressure regulator in line to keep pressure from overwhelming the needle valves. If you have doubts about your current pump, you can also replace it with another aftermarket pump that is specifically recommended for your application. If you do that, I would still use a pressure regulator and keep pressure in the 3.5-4.0 lb. range. The return line will remain plugged with the use of the aftermarket pump, as the aftermarket pump has no fitting for it, and the regulator will serve to keep pressure constant.

Also, make sure that you have a good fuel filter installed. Do a search. There have been many posts on the subject of fuel pumps and fuel filters for cars equipped with carbs.

Good luck.

Allenk · 07-16-2002, 04:38 AM

T-bird, Thanks a real lot for all your help. It's tough get into this type of project to find things "modified" especially when it's done for the wrong reasons. I like the in-line regulator option but may look to see if I can find a price on an OEM pump,not sure. I have a lot of the documentation for parts put into the car so I think I'll try and track down what the current pump is and whether it's worth keeping. Again thank you.

How about a good parts supplier? I'm assuming support of Pelican for new, how about used stuff ie. rims, moldings, lens' etc.

Roland Kunz · 07-16-2002, 03:35 PM

Hello

The Zeniths have only a feedline. However on 911 T delivered to hot areas they used a looped circuit to help bleeding vapour out from the system. This system was also retrofitet if needed.

Up to 69 the fuelpumps where locatet in the engine bay or seldom in the trunk area. With the 2,2 the fuelpump wandered under the car beside the MBC.
In MY 71 the pump wandered back to the rear torsion bar tube where it stayed untill 1977 when it wandered back to the front now fixed to the steering rack in the middle. Only the Turbo used the rearposition as it had two pumps inline.

A good pump, but to mount in the rear is the Facet/Hardi blue top. This was also original equipment from 1966 to 1969

Grüsse