I have a 1996 corvette with the LT1 engine and it has a little over 168,000 miles on it. I replaced the fuel pressure regulator, fuel pump, and fuel filter I also replaced 3/8 fuel injectors but the car still looses fuel pressure and stalls out. While the car is running the fuel pressure shoot’s up to 40-42 psi then holds at 32psi then when it stalls out it shoots back up to 40-42 psi then it drop to about 10 psi in 36 seconds. When I turn the key without started it the psi is around 41 psi then drops to about 10 psi around the same time. There are no visible leaks by the injectors, fuel lines, fuel filter, or fuel pump. There are also no fuel fumes either.

 

The bleed down your describing is usually associated with hard to start not car dies out at idle, I would be looking at cleaning throttle plates and minimum Idle and IAC operation and other things that could drag idle to drop-off

 

So that can be a reason I’m loosing fuel pressure?

 

3/8 fuel injectors...

Youre saying you replaced 3 out of 8 injectors?

 

No I see lots of people loosing their minds chasing the leak down. My 93 dump's pressure 3 seconds and runs great little hard starting but runs.
In your case if you choose to look at bleed down you can get some hose pinch off clamps have someone pressurize the system and you trap the pressure then you will know if it's in the rail or the tank.

 

yea I replaced 3 out of 8 injectors

 

Which line do I pinch off?

 

I assume you did some diagnostic to show only those three needed to be replaced?

 

Only could afford 3 at the moment lol

 

Understood. That means that one or more of the remaining injectors could be leaking.

 

There should be 2 rubber lines down on the right front of the motor for pressure and return. if not found you can pull gas door and pinch the re return line and see if if pressure stays and do same with the pressure side trapping the pressure side.

 

The way the fuel system works, is the when the ignition is turned to RUN there is a fuel pump prime momentarily, and fuel pressure should hit ~40 to 45 depending on where the regulator is set. There’s a check valve by the fuel pump that holds the pressure. If the check valve functions, the system will bleed down pressure, but the check valve isn’t even required. For example, if the valve is removed: Still primes and still t starts. Once the car starts, fuel pump/pressure runs continuously, and even if it bleeds down between RUN and START it will still start right up, especially if you time it at START about a half second after RUN position, and takes perhaps a second longer if it bleeds down between prime and start. Then once it idles, the fuel pressure is metered to manifold vacuum reference pressure, so it’s usually in the 30’s. As you jump on the gas, vacuum reduces and fuel pressure also rises.

The injectors can be removed and tested, I have one of the cheap Chinese injector flow benches. One test is the pressure check, and you can observe if the injector is leaking.

im assuming you don’t have access to a fuel flow bench, so I will say that when the injector is installed in the car… If it’s leaking enough to bleed pressure down to zero within a handful of seconds, that particular cylinder will not run well, and will also hydrolock/destroy the engine in short order. In other words, it’s probably not an injector leaking issue, fairly rare for that to happen.