i installed a fuel pressure guage on to the fuel filter and notice that the guage is reading 34psi at idle ( which is normal) but the funny thing is when i turn off the car the guage drops down to 28psi?? shouldn't the pressure be at 0 with the car off?

 

No. Most OEM pumps have a check valve on the outlet so you keep fuel in the rail after the pump is turned off. It helps a little when you re-start it. Install a Weldon, then you'll have 0 psi when you turn it off. lol

 

after you shut off the car there should be "holding press." thats how u tell if u have a leaky injector