Old and faulty Porsche 944 fuel pump valve can cause a typical hot start problem – after sitting for a few minutes starting takes ages.
This is usually caused by at least one of 2 things: faulty fuel pamp valve or faulty fuel pressure regulators.
Because fuel pressure regulators are quite expensive, I would suggest to start with replacing the fuel pump valve, which costs only 15-25 USD.
As you can see in this picture, there is a problem with the inner spring.
However the spare part costs just about 15 – 25$ it takes 1h to change it.
Spare part number: 94460895101
Locate the fuel pump and use se hose clamp pliers
Use a 6mm and a 7mm spanners and disconnect power supply
Use a spanner and loose the nut.
Use a spanner and remove the valve.
Comparison between the old and the new valve.
Put a copper waher on the new valve, tighten it.
Use another washer on the other side of the valve, put the fuel connecter on, use the third washer and tighten the fuel hose nut.
Put the cable connectors back, tighten them and put the covers on them.
I recommend cleaning the metal parts before or after the replacement with a small brass brush.
Otherwise you would have to plug the hoses before cleaning.