Fuel system question

[dhopkins]

Can anybody tell me the purpose of having a return line running back to the fuel tank? Is it to help cool the fuel? I don't notice any difference in performance when it not hooked up.

[ThomasTe]

The manual for the ´73 T/E/S states that it provides cooling to the injection pump as well as prevents the build up of vapors.

[HarryD]

From an engineering standpoint, a recirculating system allows you to maintain a constant fuel supply pressure regardless of the amount of fuel consumed. This is because you return the vast majority of the fuel back to the tank and only draw off what you need.

For fuel injection systems, the supply pressure has a strong impact on the amount of fuel actually delivered to each cylinder. By keeping the fuel pressure variation low, you can more precisely control the amount of fuel fed.

[dhopkins]

Two of my three P-cars have carbs(69S and 81SC). And whether the return line is connected or not seems to have absolutely no impact on performance. But thanks for the info.

[HarryD]

Two of my three P-cars have carbs(69S and 81SC). And whether the return line is connected or not seems to have absolutely no impact on performance. But thanks for the info.

Ah-ha... Carbs are a different animal...

The recirculating system is only needed for fuel injection. Carbs depend on a consistent fuel level in the bowl to ensure the correct amount of fuel is drawn into the throat by the venuri.

The only risk you run by disconnecting the return line is overheating the pump (if you have a fuel injection pump) because many of them use the flow of fuel to cool the pump.