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fuel pressure drops with key on and motor not run

This is a discussion on fuel pressure drops with key on and motor not run within the LT1 forums, part of the Vehicle Specific category; I have a 95 Z28 that is sometimes slow to start. I checked the fuel pressure with the key on ...

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    fuel pressure drops with key on and motor not run

    I have a 95 Z28 that is sometimes slow to start. I checked the fuel pressure with the key on and the motor not running. It runs up to 49 pounds while the pump is running. As soon as the pump stops it drops to about 10 pounds. Is there a check valve or something that keeps the pressure up while the pump is not running? I am using a Haynes maunual that says the pressure should hold steady.

    Thanks,
    Bruce

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    Senior Member bigrondownhiller's Avatar
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    How is the pressure when it is running? Are you checking it with the vacuum line disconnected from the regulator? Sounds like it is leaking down though. Could be an injector or the regulator.

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    The pressure is 41-43 with the motor running. I did not disconnect the vacumn line from the regulator.

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    Quote Originally Posted by retriever View Post
    I have a 95 Z28 that is sometimes slow to start. I checked the fuel pressure with the key on and the motor not running. It runs up to 49 pounds while the pump is running. As soon as the pump stops it drops to about 10 pounds. Is there a check valve or something that keeps the pressure up while the pump is not running? I am using a Haynes maunual that says the pressure should hold steady.

    Thanks,
    Bruce
    Yes there is a check valve and the pressure should hold for a very long time. It is fairly common for them to go bad and hey can be a pain in the ass to change, i know several people who have just cut a door in the rear deck, because dropping the tank is fairly time consuming. if its dropping really fast, (<10 sec) and has no drivebility problems its most likely the pump.

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    Thank you, I will get back to working on it in the next few days.

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