Running fuel return line

[lkadams]

My 69 912 does not have a fuel return line like the injected 911s. I'd like to run one to be able to use the PMO fuel pressure regulator now that it has a 911 motor with Webers. I have done this in the past on VW Bugs, but has anyone done this that can comment on whether it is easy enough to manage, or if I should run screaming for the hills. Obviously the PMO FPR is not a necessity, just a nice to have. The car is up in the air with the engine and trans out of it right now, so now's the time.

Thanks,
Keith

[classic]

Keith,

It's pretty easy, there should be a plastic plug on the rear fire wall, near the heater and parking brake cable.

Feed a new line through. You'll need to form the one that runs around the seat bottom, and you should see the metal tang in the far back left corner of the longitudinal on the engine side.

Hope that helps

[lkadams]

Thanks Tony - I'll have a look. I need to spend some quality Zen time laying on my back staring at the underside of my car. Which inevitably leads to thoughts of "Oh jeeze - that's rusted TOO?". HA!

[PMNorris]

Hi,
Did you fit the return line? I think i need to do this too.

Thanks
Paul

[37yrold911]

Is it safe to let the return fuel line hang loose in the tunnel? You may need to remove the handbrake, a seat and open all the ports to fasten it in there securely.

[911pcars]

You realize a fuel return system isn't required when using Webers. You could use a dead-head system. Use a low-pressure (4-5 psi), front mount fuel pump, inline filters and delete the FPR. Add a PMO manifold and FP gauge assy. in the engine compartment. KISS. Works fine unless you want to add a return line and make provisions in your fuel tank for the return line connection.

MHO,
Sherwood

[PMNorris]

Hi Sherwood,

I exchanged emails with Richard at PMO regarding this. He confirmed that the return line and regulator are only required for conversions from fuel injected cars, which mine is not. However, i like the regulator, so i will fit it and dead head it as per your setup. He did point out that as i am fitting an SC engine, i might need a bigger pump.... Time will tell.

[lkadams]

Sherwood - after discussions with my local expert, that's exactly what I decided to do - went to a low pressure pump and deadhead it. Running the return line - while not a horrible job - is just asking for one more thing to rattle in the tunnel, so I thought nah, forget it.

[dummkopf]

I find this interesting. As my car is dead-headed to the carbs like yours Sherwood. I do like a return style regulator. I think it is easier on the pump, plus it keeps fresh, cooler fuel in the lines. All of my high performance boats have return style systems. Just curious, what is the max GPH... on a say a 300hp engine?

Thanks,

Paul

[911pcars]

You can do the math here:
http://www.onallcylinders.com/2013/0...ions-answered/

I calculated about 25 GPH or about 100 LPH.

911s don't have a history of vapor-lock in the lines or fuel pump. However, fuel expansion in the carb float bowls of a sitting engine is something else, but that's more of a function of the carb and how its mounted.