Low fuel pressure and fast pressure leak after shutown
 

98 GT, 113K miles.


Today I was pressure testing my fuel system and data logging my fuel trims.


With a cold start I got 0 PSI with KOEF and 29 PSI at ide. At 1.5, 2K, 2.5K, 3K RPM loads my fuel pressure stays around 28-29 PSI and does not go down or below. Once I shutdown the car, the pressure drops by about 10 PSI within 20 min.


During the second test on an already hot engine, with KOEF, I first got 3 PSI, then I turned the key the second time, and I got 11 PSI, turned the key the 3rd time, and got around 37 PSI. After I took out the key, the pressure started falling by about 2 PSI per 1.5 min. I didn't wait on it to get to zero. In my opinion it was obvious that it was falling to quickly.


I can't find any definite fuel pressure specs with KOEO, at idle, under load and how quickly it should fall after the car has been shutdown.


I have already replaced the fuel pump, fuel filter and the fuel pressure regulator. My guess would be the faulty injectors.


Can anyone advice whether my fuel pressure is within specs or not?

Sounds like a fuel pressure regulator issue.

When I had my 97 I had what I thought was the exact same issue; I never actually tested it, but the way it acted seemed to point to a loss of fuel pressure when the car was off. From everything that I had read on the subject I felt I had a leaky injector, bu I never got them replaced so I can't be sure. So if I was you I would go for the injectors next.