Adjusting fuel pressure, engine on or pump on?

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Sep 4, 2013 | 11:16 AM

FourG63 97GST

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Launching!

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From: South Florida

Adjusting fuel pressure, engine on or pump on?

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?

Sep 13, 2013 | 04:44 PM

07kyeringt

Staging Lane

Joined: May 2013

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From: Cedar Rapids, IA

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?

Sep 13, 2013 | 08:22 PM

FourG63 97GST

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Launching!

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From: South Florida

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

Oct 2, 2013 | 06:48 PM

joecar

TECH Senior Member

Joined: Apr 2002

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From: So.Cal.

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.

Oct 2, 2013 | 06:49 PM