Short Bosch Fuel Pump questions

[IXLR8]

Hi--

I have a few questions about the short Bosch fuel pump and its fuel connections. I have a 65 230SL, VIN 10467

I see some some cars with a "T" fitting in the fuel supply line with one side feeding the injection pump and the other side returning to the fuel pump.  Other cars have only a single fuel line feeding the injection pump.

1) What is the purpose of the return line?

2) Where does the return line attach to the fuel pump?

3) Why do some cars have the "T" fitting and others do not?

How can I know if my car should have a "T" fitting or a straight feed line to the injector pump?


Thanks in advance for your help.

Joe

[ja17]

Your injection pump has a return fitting on the IP. It is where the fuel returns to the fuel tank.

These fittings act as regulators creating pressure in the fuel system before the fuel returns to the tank.  Some refer to them as regulators.  There are two types of return fittings. One has a small hole (orifice) to restrict fuel return. The other type has a spring loaded check valve.  If your pump has the fitting with the orifice do not use the "T" by-pass  fitting. If your has the check valve fitting, you can use the bypass. 

[George Des]

Joe's right. You should not need the T fitting on your car if you have the R11 FI Pump that was original to the car.

George

[IXLR8]

Thanks, Joe and Des--

I have an R11 IP and a single line fuel feed.

So, I'm done below the car and now onto the top side.  18 months into what I anticipate being a 36 month restoration journey.

Thanks to all Pagoda members for their encouragement and vast reservoir of knowledge.


Joe