The fuel pressure is modulated by engine vacuum. That is the purpose of
the vacuum hose at the back of the regulator. The idea of this is to
help compensate for the actual pressure difference of the intake
manifold versus the fuel pressure supplied to the injectors. As the
vacuum increases (real pressure drops) less pressure at the injectors is
required for a specific volume of fuel to be delivered when the
injectors open. Stmbling problems are usually caused by intake vacuum
leaks, uneven fuel delivery (bad injectors), bad intake valves or guides
or excessive deposits on the back of the valves.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of jesse johnson
Sent: Monday, September 06, 2004 3:18 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Fuel Pressure Question...

Hey All,
In trying to find out my van's stumbling issues.. i rechecked the fuel
pressure. Seems that i run at right around 30 psi during idle but if i
rev the engine.. or hold the engine at say 3000 rpm or so.. the
pressure will drop down to like 25 psi or so. Is this normal? Seems to
me that it should remain at 29 no matter what the load. This might be
why i am having stumbling on take off.. and is worse on hot days. Any
thoughts on this? The fuel pump is original and has 170,000 miles on
it.
thanks all,
jesse
89 carat
86 scirocco 310,000 miles and going