GT500 Fuel pressure when not running

[Skarkull]

I'm having erratic fuel pressure showing on my gauge, so I'm trying to trouble shoot the issue. I have the GT500 fuel pump setup on my 05, and I'm showing 28.75 psi after letting the system prime, but not turning the car on. I'm pretty sure it's the gauge, it is only showing around 18 in the cabin. What should it be not running? I did search, and all I found was where it should be at idle, 30 is what I hear / saw posted on here alot, any input?

-James

 

[hamish]

I see mine hit about 50psi
about 30psi at idle.

 

[86GT351]

According to Mitchell on Demand for an 07 GT 500 KOEO (Key on Engine Off) pressure should be between 35-70. KOER (Key on Engine Running) should be between 27-37!

 

[BruceH]

A GT500 should measure 36 koeo and 44 fuel rail pressure while running according to the manual.

http://iihs.net/fsm/?dir=39&viewfile=5.4L 4V Mustang.pdf

An interesting side note is the fuel injector minimum pulse width is listed at 3.5ms!

 

[Skarkull]

Anyone else have issues with AEM gauges? I have 3 and 2 of them are giving me issues. Only one that seems to be working legit is my AFR.

 

[BLKS197]

Mine primes to about 50 when I turn the key to on, at idle I see just under 27-30.

 

[AutoXRacer]

Yep, mine idles at 40 PSI.

Priming goes up to 50; typically 47-ish.