'71 911E MFI starts cold but won't start when warm

[71Targa]

So it turns out the brand new fuel pump from Porsche in Germany is pushing 3 pounds of pressure instead of 10. 3 pounds is for the carbereted engine and 10 for MFI. Replacement on order.

[edmayo]

Is it a 009 or a 001. 001 is the FI pump. (Those are the last three digits) And where are you measuring this pressure?)

[Boulder Bob]

Definitely a fuel starvation issue. The check valve in the fuel filter was not working. Replaced that and we were able to get it to start hot, but after running awhile it started to lose fuel. We are going to replace the fuel filter, the mechanic said he is seeing some debris in the fuel. We replaced all the fuel lines recently (for a second time), perhaps deteriorating fuel lines have fouled things up. I think we need to have the MFI pump rebuilt. It has a brand new fuel pump at the front.

is the check valve you are referring to the same thing as the overflow valve?

[71Targa]

In the end it was two issues. The check valve at the fuel filter was not functioning, it was wide open, and the fuel pump was going bad. First replacement pump was the wrong one, for a carbureted car, the correct one for an MFI solved the problem. Starting and running great. Thanks to all who responded!