Mike,
Sorry for not jumping in this sooner. Eric has my number.
First, fuel pressure should be 33-39 psi during a static pressure test. Running, I believe it is suppose to be 28-42 psi minus 1/2 the manifold vacuum pressure. Thus with increasing rpm and/or load, there should be a drop in fuel pressure at the rail.
Second, the Fuel Pressure Regulator controls pressure at the fuel rail by controling return fuel flow to the fuel tank. It regulates rail pressure by adjusting return flow based on the manifold pressure.
Third, if I remember correctly, pressure at the fuel rail after the engine is shut-off should be a minimum of 20 psi after 5 minutes [key off].
So, it appears that the problem may be the pressure regulator. If it were a weak fuel pump, while pressure at the fuel rail would be low and cause the symptoms you're experiencing, pressure at the fuel rail would not immediately drop to 0 psi after the pump is deenergized. With a bad pressure regulator, pressure at the rail while the engine is running would reflect the free-flowing system pressure with no restrictions to build pressure at the fuel rail. But, . . . .
Eric stated that only the pump was replaced. It is possible, that if the pump was not properly mounted within the sending unit, that fuel is leaking at the point where the pump is [trying to] feeding the fuel feed line. Additionally, if there is a "leak" there, it would allow for rapid pressure bleed-off as there is nothing to prevent the fuel from free-flowing back into the tank, once the fuel pump is deenergized.
Between when the car was running fine and now, you've had both the fuel rail out to change injector seals, and the fuel sending unit to replace the fuel pump. If the problem began immediately after you replaced the injector seals, it would suggest the fuel rail/pressure regulator as the problem.
You might want to post some links to your prior threads on the injector seals change and the fuel pump change for reference.
So there's two ways to approach this. One, try a known good pressure regulator from another running SHO, where you can test the fuel pressure
prior to removing it and installing it in your SHO. Two, drop the tank and try a known good fuel pump/sending unit from another running SHO, where you can test the fuel pressure
prior to removing it and installing it in your SHO.
In my opinion, the latter would be the easier of the two in terms of the amount of wrenching required - *and* you can leave the fuel tank on the ground while you're swapping/running the tests until you know you have fixed the problem. Swapping the regulator will require at least two removal/installs of the intake and aft fuel rail.
Then recheck the fuel rail pressure.
Fuel filter didn't fix the problem either.... It is holding no pressure in the lines after the car is off. While running, (when it does), it holds just enough to run and not very well either. Sometimes dies. Stumbles at 3500 rpm. SOMEBODY PLEASE HELP ME!!!
I caved in and bought a fuel pressure gauge. When I prime the motor, the gauge reads "0". When the car is running, it reads: around 15-17psi. I repeated this process twice... same results both times.
I have done a little research on the forum in the advanced search, "hold fuel pressure", but without the quotes. From what I have read in what others have posted it is pretty much exactly how my car is running right now, especially compared to the 3rd and 4th threads in that search, where it talks about hesitating and bogging down while accelerating. Taking 3-5 trys to get the car to start when it is cold. Then when it is hot runs, irregular and rough and boggs really bad.
From what I read, what I see on the gauge, and what I have experienced, I think I need to get a new fuel pump (again). I purchased a Cardone, from RCM, I want a return and refund. I am thinking of going with this one as the replacement:
http://shosource.com/catalog/product_info.php?products_id=41{2}116
Am I thinking along the right lines??
I've seen several pumps bad out of the box.....
