asu11

iTrader: (7)

How long should it take for fuel pressure to bleed off after shut down or at what rate should it bleed down?

BiFfMaN

iTrader: (3)

Should hold *Close* to normal for over a Minute on a Stock system, But typically you see a drop from the Pressure regulator once pumps are off.

You should not see a Sharp drop, full pressure drop after 3 seconds.

I use the term Close loosely because this will be very dependent on your fuel system setup.

barneyb

Ideally, a pump with a check valve, when the pump shuts off, the pressure should be there when the car is started later. But check valves leak. How much a check valve leaks determines the leak down rate. I suggest its normal to find some fuel pressure maintained for the better part of an hour.

Cars with bad check valves seem to start as easily as cars that maintain pressure so don't understand the importance of this.

BiFfMaN

iTrader: (3)

It is so the pumps can prime before the starter is used...and good fuel pressure for the cranking cycle. Once its started the starter is disengaged and pumps will now run.

But you are correct, there is a check valve in most fuel pumps. as it gets older it will have a harder time holding pressure.

barneyb

The pump is always immersed unless the tank is empty. Most cars with 50K on them will leak down the fuel pressure and they still start and run. Now, most cars start operating the pump as soon as the key is turned to run before turned to start. This is know as a prime but it is to start getting the fuel pressure up. Not sure the Evo does this, I'd need to check the literature. Anyway, the one purpose I can see the check valve serves is to splash you in the face when working on the fuel system, lol. Seriously, maybe it is to maintain some pressure if the fuel pickup is uncovered as we zoom around a corner.