MFI Overflow Valve

[Boulder Bob]

On the upper part of the fuel filter console there are three fuel line connections. The one that goes back to the fuel tank is called the overflow valve in my parts book. I have also heard it called a check valve. Is this valve supposed to stay closed until the the filter is full and then allow fuel to flow (only one way) back to the tank? How much pressure are we talking to open it? Are the other two top connections simply 90 degree fittings?

What would happen if the overflow valve got stuck (open or closed)? Has anyone had any issues with this valve? Can it be tested? If it got gummed up, could it be soaked in a solvent to un gum it? What solvent?

Thanks.

[gled49]

The cheek valve sets the pressure in the fuel loop to the Injection Pump. I run a fuel gauge in my race car from the cold start socket and my fuel pressure runs from 13 psi to 8 psi depending on air density: hot - cold - morning - afternoon. The unit can be cleaned with brake clean, or just about anything. Any simple blowing / sucking test can check the valve but a pressure gauge will be necessary to check pressure. I got some water in my fuel a few years ago, and sure enough when the engine started missing, the fuel pressure was '0'. The paper in the fuel filter console swelled with the water and stopped fuel flow. The 2 hollow bolts and banjo fittings are straight thru. the fitting on the bottom of the fuel filter is straight thru. The return fittings has a spring and check ball inside. By the way, all fittings must be installed in proper location, with the check valve opposite mounting flange of the console. Gled

[Elferhelfer]

Hello together,
I have some problems with a 911 E engine and the MFI and so I was looking for some information and found this post. A little bit older, but it may help….

Does anybody of you know the opening pressure of the overflow valve (901.110.915.00)?

In the picture it’s called pressure regulator fitting….

[Boulder Bob]

Hello together,
I have some problems with a 911 E engine and the MFI and so I was looking for some information and found this post. A little bit older, but it may help….

Does anybody of you know the opening pressure of the overflow valve (901.110.915.00)?

In the picture it’s called pressure regulator fitting….

doesn't exactly answer your question, but see my post #15

http://www.early911sregistry.org/for...260#post871260

[edmayo]

Hello together,
I have some problems with a 911 E engine and the MFI and so I was looking for some information and found this post. A little bit older, but it may help….

Does anybody of you know the opening pressure of the overflow valve (901.110.915.00)?



In the picture it’s called pressure regulator fitting….

It is mentioned in the post right above yours.

[Elferhelfer]

Thanks a lot for your help.

I was looking for the overflow valve, return line to fuel tank... Meanwhile I found some additional information. The part number of the overflow valve is 901.110.915.00, Bosch part number 1 417 413 009. The electric fuel pump should deliver around 1 bar, 14 PSI…

Opening pressure is 0,6 bar, around 8-9 PSI.

[edmayo]

The MFI pump is rated to deliver about 30 PSI.