weird noise when i shut car off [Archive] - Forum


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04-15-2005, 02:10 PM
i have a breather on the back valve cover. it is making a sucking noise. the problem arises because of my car losing fuel pressure. i have a gauge on it and the car runs 34 at idle and 40 at wot. when i shut the car off it loses pressure at quick rates, going to 0 psi within 2-3 min. would this be a problem?

04-15-2005, 05:28 PM
There are a few things that can cause fuel pressure leak down after the car is turned off. First is a fuel pressure regulator. To test that start the car and check the pressure. You should have about 40 at idle. Then shut the car off and unhook the vaccum line to the regulator. Look to see if gas comes out of the regulator. Another thing is that the injectors could be leaking down. To check that, youd have to get the rail off the engine and prime the fuel pump and see if one of the injectors are releasing pressure. The last is that the leak down valve in the pump is letting gas go back into the tank. Basicly no way to test for that but if it isnt the injectors and if it isnt the regulator, then it is probably the pump.

04-15-2005, 10:28 PM
Fuel pressure dropping to 0 in 2 - 3 minutes would suggest a FPR problem to me. I haven't really seen alot of FPRs on the 3400 leaking into the vacuum line. Its usually external and drips onto the lower intake. Either that or it just bleeds down internally.

Usually when a fuel pump check valve isn't holding pressure it'll drop like a rock and in a few seconds you're at 0.

To test the fuel pump you clamp off the rubber part of the return line going to the fuel rail. Have someone cycle the key to run for the pump to prime and then clamp off the rubber part of the feed line. If no pressure drops then your fuel pump check valve is bad. Time for a new fuel pump. However if the pressure still drops you need to look at the injectors or fuel pressure regulator.

04-15-2005, 11:16 PM
another problem is that it is running 34 psi at idle and 40 at wot. it is not running enough pressure when it is running. i will check the fpr tomorrow though. thanks