Fuel Pressure Question

[clacey]

I have a 91LS400 with 213000mi. I am wondering how the fuel systems works. My fuel system seems to be loosing pressure as it sits with the engine off.

Is this normal or should the system stay pressurized after the ignition is off?

The car takes about 4 secs to start for the first time, if it has set overnight. Otherwise, it starts immediately.

If it is supposed to stay pressurized, What could be allowing it to disipate? The fuel pressure regulator or the fuel pump?

If it isn't supposed to stay pressurized, could the fuel pump be getting weak or could the fuel pressure regulator be out of spec?

Other than this there are no visible leaks and the car runs great.

Can anyone help? Class? Anyone?

Thanks,

CL

[99lsguy]

Here's some service specs :

serdat.pdf

[99lsguy]

Fuel pump regulator check:

comp.pdf

[99lsguy]

And lastly, fuel pump relay check:

insp.pdf

[clacey]

Thanks a ton for taking the time to post these.

Am I correct in assuming that the system should stay pressurized when turned off?

Thanks,

CL

[99lsguy]

I would think so.....

I counted out 4 secs after reading your post...that's a long time cranking!

Especially just overnight... maybe after a month or two....I could see it.

Those pdf's are all from my 99 LS service manual, so let me know if you need more. If the fuel pump is faulty, it's behind the rear seat! I'll send some more diag/relay possilbities....

99

[99lsguy]

Fuel pressure regulator componets....

I've got the inspect, remove, and install if you want....

comp.pdf

[VMF]

nice job 99ll:) where did you get your manual in pdf?

[99lsguy]

nice job 99ll:) where did you get your manual in pdf?

Thank you...

It's perfect for LOC applications. Pro grade quality.

ShardAuto was the seller.. off ebay

I've got the paper manual (vol 2) too - so I picked this up mainly for the :

Service specs

Maintenance

Intro

Diagnostics

which are in vol 1 - didn't want to spend the $ for regular manual