I may of had this in a different post before but I need to get this figured out and appreciate all the help.

I have replaced my fuel pump twice, tried two different regulators, and checked for leaking injectors. I had the rail off, hooked up with the injectors on and I can hear a hissing noise by the regulator maybe the O ring going into the rail is bad? It is brand new though. Could the inside of the rail be bad? The pressure bleeds of instantly and it's only ever at 33psi. If I remove the vacuum it goes up to 43. No gas our gas smell in the vacuum line.

How can I test things to see what's going on


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You know about the gray jumper that turns on the pump when you put it to 12 volts? It's in the wire bundle just ahead of the PCM towards the front of the car (pass side). If you've tried that and the injectors are not leaking, then you probably have some leak back in the sending unit with your hoses or pump check valve.

 

Yes I know that wire....lol

if a hose is bad in the back, why can I hear a hissing at the regulator?


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Car also surges while cruising and it always smells like it's running rich.

usually on my way to work i'm cruising at 1500rpm but it will drop go back up drop go up. And keep doing it til it like catches where it's suppose to be then it will be fine for a while but it always does it.


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43psi without the vacuum connected is the GM spec (actually 43.5psi, but anything within 41-47psi is acceptable).

Attaching the vacuum line drops the pressure proportional to intake manifold vacuum. A 10psi drop is on the high side, but not unreasonable.

Have you checked the vacuum line to see if that is the source of the hissing?

When your RPM is dropping and going back up (I'm assuming that's what "it" refers to) does the fuel pressure vary in the same sequence?

 

I had the fuel rails laying with the fuel lines hooked up, no vacuum line hooked up at that time. I was putting the new valve in the shrader and seeing if I could tell what the hissing sound was. it is coming from the area where you push the fpr into the rail. the fpr and oring are new, and I tried a different reg. Car takes forever to start, im assuming from the low pressure. I could never see fuel pressure when the car was surging. I am going to purchase an electronic fuel pressure gauge then I will see it when im driving. say a line at the pump is the cause of the pressure issue, what could the noise at the regulator be?

 

Have you had any wetness or visual fuel loss in area you hear the hiss? May want to try and put paper towel in area to see if you are leaking any fuel. Also smell it for gas smell(the paper towel). As Fred said be certain you vacuum line isnt the problem. I would think if it is on the fuel side you would have fuel leaking somewere and I dont know what if anything would have the ability to have a contained fuel leak other than the regulator but I dont know near enough (or sticky injector).


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I had the rails in my hand and it didn't leak at all, just the noise I could hear. Thought I saw something before about crimping the lines to rule stuff out or pinpoint something?


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I never had a pressure problem before my pump quit and I had to get a new one. Then I had this problem and got a new pump and it was the same. So I am kinda leaning towards a line at the pump. How do I check them?


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Can you change the rear fuel lines without dropping the tank?


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Just got my electronic fuel pressure gauge so I'm going to hook it up and read while driving and also check the rear fuel lines.can the O rings in the fuel lines be replaced and if so what do I look for?


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Checking or working on the fuel lines at the rear requires dropping the tank, unless you opt for cutting a "hatch".

 

I have a hatch cut already as I changed the pump once then I had this pressure problem so I replaced the pump again and it's still there. I don't know if the lines at the pump got messed up but I will check them this weekend. If an o ring is damaged how do I go about replacing?


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Just got done hooking up electronic fuel pressure gauge. Reads 38psi. The mechanical gauge read 33. I have 43 all through out the rpm's. Bleeds off immediately.


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So it appears your only problem is the rapid bleed off after the pump primes. Check valve in pump, leaking line, leaking injector(s), fuel pressure regulator. Appears you have already checked these out. This problem typically only affects startup time, and not the way the engine runs. Do you have an extended cranking time?

Is the "hissing" you hear simply the fuel pressure regulator doing its normal operation, which is closing down on the opening to the fuel return line, to control the pressure?