FourG63 97GST

iTrader: (1)

did a return setup, (primary and secondary fuel pump) I've always read turn the engine on to adjust the pressure. But what's the reason for that, can't I just turn the pump on via hptuners? the needle stays steady that way and the reading is accurate vs engine on and the needle flutters about 2-3psi. What logic am I missing here?

07kyeringt

Like just priming pump?.. If you are just turning on ignition but not starting fuel pressure will happen. but will slowly dicipate. If car is running you have constant fuel being pumped therefore more accurate adjustment. You have a Fuel pressure gauge right?

FourG63 97GST

iTrader: (1)

no not priming with the key, turning the pump on via hptuners. constant pressure

joecar

The idea is:

1. to have the pump running (does not really matter how)

AND

2. the FPR reference must see barometric pressure during rail pressure measurement.

joecar

So:

a. if pump is running with engine off, FPR reference is seeing BARO.

b. if pump is running due to engine running, you have to disconnect the reference hose during measurement.