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| 944 Failing fuel pressure leak down test https://forums.tipec.net/viewtopic.php?f=25&t=25397 |
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| Author: | abainbridge [ Thu May 29, 2025 7:49 pm ] |
| Post subject: | 944 Failing fuel pressure leak down test |
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. |
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