Fuel pressure questions

Lyndon302 · 01-20-2022, 04:24 PM

On quest to sort my carbs
I've fitted a pressure regulator. I have no return line which is the issue I think.
On running I can set to 3psi. With the car off and IGN on it just keeps building up. I have seen 6 PSI. Also I'm guessing at a high speed it will drop below the 3 PSI.
Car seems to run fine as is. I haven't beat on yet but I'm sure it be fine.as it's not a race car.
I have viton needles on order. This is all to sort a flooding problem I had on cold s start up.
Of interest if I let it pump and get high PSI on a start up it will put black spots on my garage floor. So it's definitely getting excess fuel leaking into my engine.
My practice is now 4 pumps. IGN on and crank asap. Seems to work fine.
Am I all good with this pressure regulator or ??
Thanks lyndon

snbush67 · snbush67's Garage

No, not good. You need to flow the excess pressure back to the tank.

What model car and what fuel pump?

Lyndon302 · 01-20-2022, 04:59 PM

Quote:

Originally Posted by snbush67

No, not good. You need to flow the excess pressure back to the tank.

That's not much work. I have no provision in my tank or lines running thru the car
Lyndon

icarp · icarp's Garage

Hey Lyndon
Shane is right , you need to have a regulated return.
PMO sells the one I choose to use , but you can make on by putting a Tee in the pressure line run the free line to the regulator and carbs and the other side of the Tee back to the tank .
The trick is to put a small plug in the return line with a 1.5 mm hole in it , this allows the pressure to bleed off to the tank,
Ian

Lyndon302 · 01-20-2022, 05:30 PM

Ok it's a 68 911
My Pump is a pierburg efp085pie.000
3 to 5 psi.100lph.
Lyndon

icarp · icarp's Garage

I remember Lyndon,
If you don't have a return line to the tank you can install a 60 degree y pointing back to the fuel pump suction side , with the regulated return line .
ian

Lyndon302 · 01-20-2022, 07:40 PM

As per my diagram. I can do all this in the engine bay with a few tees and make a restrictor.
Lyndon

icarp · icarp's Garage

Lyndon , yes those are the basics .

Lyndon302 · 01-25-2022, 01:48 AM

I've put a bridge in. Also a 8mm bolt X 10mm. Drilled to 1/8th. Then Solderd and drilled to 1.5 mm. Put halfway in the bridge.
I can adjust to 3psi perfectly. No build up on engine shut down and nil variation on revs in neutral.
A road test tomorrow to confirm.
Thanks lyndon

Tremelune · 01-26-2022, 06:48 PM

Why, ah...why all the plumbing? My car has Webers and a single line and low-pressure fuel pump in the front...

With regard to the return loop (neat trick), how did you figure out 1.5mm restriction? I'm thinking of going EFI, and I'm not sure what to do about a return line...

Lyndon302 · 01-26-2022, 08:30 PM

My car has one line from the tank . The pump is in the engine bay. That's front the factory.
After 52 years I guess all the pumps are a little high that you buy now. After about 18 mths off trying to this correct I think I've got it. It's starts idles and runs better than ever. I should have fitted the pressure regulator long ago.
Lyndon

Lyndon302 · 01-26-2022, 08:31 PM

Quote:

Originally Posted by Tremelune

Why, ah...why all the plumbing? My car has Webers and a single line and low-pressure fuel pump in the front...

With regard to the return loop (neat trick), how did you figure out 1.5mm restriction? I'm thinking of going EFI, and I'm not sure what to do about a return line...

Another member suggested 1.5 mm