when i turn my car to the run position, i build fuel pressure to like 48psi, then after the fuel pump stops priming the pressure clicks off to like 30psi and then it like falls to zero very quickly it used to just build pressure to 48psi and then only click off to about 40psi and would stay there... now the pressure seems to be falling off completly, why

 

Do you have a delayed start? I think its the check valve in your fuel pump. I have the same issue, how many miles on your car?

 

You have a fuel leak somewhere, plain and simple. Here are all possible causes:

-broken fuel lines
-faulty check valve in the tank pump
-leaky injector or injector o-ring seat
-stuck open injector (can be very dangerous)
-faulty fuel pressure regulator (pull off the vacuum line on the regulator, and see if it is full of fuel...if so, you're also running rich, as fuel is leaking from the regulator back to the intake manifold).

Go down the list and see what you can rule out.

 

I think it's either a leaky injector or a faulty check valve. I have some 30lb Accel injector's in there, also my fuel pump is the granatelli 250lph.

I will pull the fuel rail off and see if they are leaking. I just barely noticed this, but the car has been getting low BLM'S lately so it kinda all add's up now

 

Well scratch the leaky injector's. I pulled the fuel rail and they all hold pressure while the car is in run so that's not it.

If it is my fuel pump check valve or what not, how bad is that? I mean the car hold's pressure when it's running. Where is the check valve anyway's?

 

To check for leaky injectors, you need to jump the fuel pump prime connector so that the pump stays on. If you leave it in RUN, the pump shuts off after 2 seconds.

 

i just noticed mine does this also. i have the same pump and 30# fms injectors. does the same in "run" and when reving it will dip from about 35 down to 30 then back up. when i went to the dyno last week the fuel pressure was 50lbs and i was running rich off the scale. lt1 edit wasnt working so we adjusted the regulator (aeromotive) down to 35 and i dynoed 380rwhp 330 with 50lbs. im going back to the dyno next week to have it tuned. any comments on what could be going on?

thanks

 

Yea but I watched the injector's while my buddy sat in the car and turned the key to run and he watched the fuel pressure guage as is went from 48PSI to ZERO with the key at run and i didn't see anything leaking out of the injector's. So that would lead me to believe that it has to be leaking somewhere else right?

 

OK I was just reading trough some post's and i noticed that people that are having the same problem as me with the fuwl pressure dropping are also having a hard time starting their car. I also have had a hard time starting my car lately, I crank the motor over and over and I have to depress the gas pedal to get it to crank over

So what's the deal then? I know it's not the injector's, already checked those. My fuel regulator isn't hooked up to the intake manifold via the vacum tube, so i would see fuel squirting out of there if it was leaking from there. So it's gotta be something in the fuel tank, cause i know my lines aren't leaking anywhere.

So if the problem is in the fuel tank then what would it be? I have a granatelli 250lph pump so what do I need to check for when I pull it out? I was reading something about a "check valve" where is that?

 

The check ball is internal to the pump. I don't believe it is anything you can "check" (or at least repair). However, you can prove where the probelm is by this procedure.

 

yeah mine hasnt wanted to start a few times in the past couple weeks also.. well atleast if its the pump i already have an access panel to change it

 

going along with that, heres a bit more detailed prcedure, but don't clamp any plastic/metal lines...

http://www.gnttype.org/techarea/fuel...sys_check.html

 

aright i did the test at http://www.gnttype.org/techarea/fue...psys_check.html i now beleive it is my check valve so ill change the fuel pump soon(brand new 255l from summit). is this hurting me on the track i just traped 112mph with a **** poor launch (spinning thru 1st) i also pulled the injectors out of the manifold and turned the key on/off/on/off etc and they didnt leak but when i turned the key off a couple of them spit alittle fuel. is it safe to leave the vac line off the regulator? constant 40psi, feels stronger when reving with it off. 35psi when on drops to 30-31 when reving.

 

I don't know what you mean. It is basically the same procedure and does say to clamp the lines. It is also not f-body specific and mentions rubber lines of which there are none on the f-body.

 

I'll have to try that procedure today.

How bad is this to leave the pump like that? Does this affect performance? I'm going to fix it I just wanna know how bad this is affecting me.