08 GMC Sierra Fuel pressure testing at fuel Rail

[Frank earthrowl]

What is the pressure at the rail with key on and the what's the PSI after starting engine??  Thank You

[davester]

It's my understanding it's the same as the earlier port injected trucks, 60 psi +- a couple psi.  It should go to that pressure with key on, and remain at that pressure once the engine is started, and when the engine is accelerated.  It should also stay at that pressure for some time after the engine is turned off, but I don't recall at this moment how long it should take to drop X psi.  The pressure can drop briefly as the engine is changing speeds, but should quickly return to full pressure.

[swathdiver]

4 hours ago, Frank earthrowl said:

What is the pressure at the rail with key on and the what's the PSI after starting engine??  Thank You

Mine has a FlexFuel 5.3 and runs at 43 psi which is commanded state.  Key on, the pump goes to 55-60 psi.  Supposed to not lose more than 5 psi after key is off.