Porsche Enthusiasts Club Forum

My car fails the fuel pressure leak-down test. ie https://www.clarks-garage.com/shop-manual/fuel-01.htm. The pressure drops to almost zero after 20 minutes. As a result it takes more cranking to start than it should.

I bench tested the fuel rail and injectors. They don't leak. I've replaced the check valve on the pump twice and I've replaced the fuel pressure regulator. The problem persists.

I have found that if I remove the return-to-tank hose from the fuel pressure regulator and replace it with a stop end, the pressure is retained. This stops the fuel exiting the fuel rail via the regulator. So I suspect that both the old and new regulators I have are faulty. But this seems unlikely.

Here's a video of the rate at which fuel is seeping past the regulator when the fuel rail has about 1 bar of pressure:
https://youtube.com/shorts/sCE6dLCpJjo

It seems like it couldn't possibly hold pressure with the regulator leaking like this, but I'm worried this isn't a valid test for some reason.

Both the in tank and post-pump filters are all new too, and I cleaned the tank out. There's no sign of any leaks in the fuel lines.