TT Oversteer

My '77 3.2 conversion came to me with a 911.608.102.02 fuel pump installed. It looks like this is a pump intended for CIS cars.

The 3.2 Carrera pump is listed as 944.608.102.04.

I know CIS runs higher system pressure than Motronic. Does anyone know if my installed pump would cause running issues with the Motronic system or will the fuel pressure regulators be able to correct and provide the correct 2.5 bar system pressure?

What is the fundamental difference between these two pumps? How different is their respective output? Can I use the earlier pump or do I need to buy the later one?

I intend to check fuel pressure once I get a guage but I don't have one at the moment!

rusnak

Hey are you near Fresno? I can let you use my fuel gauge, but HF is having a parking lot sale today through Sunday. You might get a cheap one there.

I'd not use the CIS pump. You have to run the 944/911 3.2 fuel pump. I think the difference might be around 20-30 psi, which is a lot.

TT Oversteer

Thanks rusnak! I would take you up on the fuel gauge if I was closer to you but I'm up in Auburn. I'll look into HF; good tip. Yes, I have a feeling the CIS pump is not right but I'm hoping someone on here has some fuel pressure values for the two pumps or knows what the range of correction is for the fuel pressure regulators on the 3.2. This car is still not as fast as it should be and I'm still sorting things out. My fuel injectors are on their way back from Witch Hunter and I'll find out next week if any of them were bad.

rusnak

I finally remembered to grab the info from my reference materials:

911SC fuel pump pressure (engine off, pump running): 65-75 psi
911SC fuel delivery volume 1.06 qt, 30 seconds @ 12v

3.2 911
Engine off: 36 psi
Engine running: 29 psi
Engine running w vac hose removed fr pres regulator: 33-39 psi.

Source: Bentley Publishers, Cambridge Mass