hiss noise when key turned on, same time fuel pump is on

[ScottJackson]

So I bought Nicholas Chopp's '93 Q and had enough time for about 5 minutes of checking it out. What I've noticed is that the fuel pump makes noise when the key is first turned on and it keeps the same volume and pitch until it shuts off several seconds later. That's not so terribly strange, except that there is a light hiss noise coming from the top of the motor... like a steam noise. It will almost start, but won't. It hits a little every now and then but that's all. The hiss noise sounds like it's coming from under the intake plenum. I wonder if maybe it could be a failed fuel pressure regulator and the sound is the fuel in the fuel lines. Anyone have any experience with this? EDIT: maybe this should be in the Infiniti Online mechanic section?

[qship96]

vacuum leak?

[ScottJackson]

nope, this noise comes on with the key... no cranking the engine over.

[maxnix]

Check vavle in the evaporative cannister system?

I think it is up front under the MAF.

[Jesda]

SNAKES!

[ScottJackson]

on a mother f'n plane! The noise isn't from under the MAF area. Definately plenum area. I'll have to test it out next weekend by pinching the return fuel line with pliers whilst my dad turns the motor to see if that's the issue. Keep the suggestions coming though! Thanks!

[texasoil]

sounds like fuel pressure regulator is leaking past (trash in it? ) Can't imagine the spring breaking. Would be interesting to do a post mortem

[ScottJackson]

Any suggestions for de-leaking it? Maybe feed the regulator lots of vacuum and at the same time sending compressed air into the opposite end of the fuel rail? I just really don't want to pull the plenum if I don't need to do so.

[Q45tech]

Before you go DESTROYING components use your technican stethoscope to ACTUALLY pinpoint the noise.

[ScottJackson]

Yes, I'll check it out more before I do something as incredibly stupid as only rednecks like myself are capable of doing. I just like to think ahead while I'm up at school so I can have several plans of attack when I actually get home on the weekend to look at the car a bit. If it does sound like it's a pressure regulator at fault, maybe I'll disconnect the rubber fuel hose just in front of the plenum, attach two longer hoses that go into a bucket, and jumper the fuel pump so it goes "balls out" and maybe with some vacuum to the regulator it'll spit out whatever may be clogging it. Maybe it won't, but I think it'd be worth a try because if it doesn't work, I'm taking off the plenum anyway to replace it. Of course, maybe it isn't the fuel pressure regulator. Have to check it out a bit more before messing with it too much.