I need a little help to understand this.Here is the question.I put a fuel pressure gauge at the port and turn the key on engine off several times so i got the pressure going up to 40psi but when i shut off the key the pressure went down as fast it went up.So i realized that something was wrong with that.Took the fuel rail out to check a injectors leak and found nothing, then i disconected the return line and got fuel pooring from the port.Any idea what's wrong......

 

Define return line? You mean the vacumn line to regulator or the rail return line (adjacent to the main feed line...the two lines coming into the rail). Mine does the same thing, it has to do with a check valve in the line somewhere. Won't hurt performance as far as I know.

 

I'm not aware of any check valve in the fuel lines. If your fuel system isn't holding pressure when the pump stops, and you don't have a leaky injector or o-ring or other major leak, the fuel pressure regulator is leaking. Could be trash holding it open or, like mine was, the rubber diaphram is old and stiff.

 

Hmmm but doesn't this go along the line of change a fuel filter. Before I did it and everyone else here we ask about pressure being in the system. The book say to watch out. But when you do crack the line lose. There is nothing but a trickle.

 

It doesn't take long for the pressure to bleed off. You aren't dealing with a large volume of fuel. I've never bled the pressure when changing the fuel filter. All I ever got was a very, (VERY) brief squirt of fuel and a little trickle after. The books warn you like that because of the LAWYERS. I work on hydraulics at Caterpillar, and you do need to be careful when breaking loose high pressure hoses and lines. If part of your body is in the way of a high pressure squirt of fluid you could be injected with fluid and get sick even die if it hits an artery or vein. This isn't really a problem with 40psi and the small volume of fuel in the lines, just keep your head out of the way, fuel in the eye ! But the LAWYERS like to be careful, hence the warning.

 

Is not a check valve(sorry about that),is the shradder port where u put the fuel gauge anyway the pressure doesn't hold for even a second and is happening since i changed the fuel filter.Anyway i am going to check the diafragma since i see a lot of fuel returning to the tank.

 

You should see lots of fuel returing to the tank. The stock pump probably flow 4 times as much as you need.