Date:         Tue, 3 Apr 2018 02:07:27 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Fuel tank problem solving (Almost)
Comments: To: OlRivrRat <OlRivrRat@comcast.net>
In-Reply-To:  <4C29DA9A-2420-40D1-A431-3C7E1B3898F6@comcast.net>
Content-Type: text/plain; charset="UTF-8"

>
> But another issue was a failing vacuum
> hose to the fuel pressure regulator; mine was probably original and no
> longer stiff enough to hold a vacuum.  I think this was part of the problem
> in my case of having insufficient fuel flow at the engine (and a loud,
> whining fuel pump).


Leaky vacuum hose at the regulator would cause the fuel ring pressure to
rise compared to what it should be with running engine, thus giving you a
richer mixture (which might be compensated for by the oxygen sensor in
steady state operation but would cause a problem with varying throttle).

Noisy pump is usually cavitation (bubbles forming in the fuel between tank
and pump) caused by a restriction in the inlet from the tank or clogged
pre-pump filter.

Also, does the fuel pump cycle on and off depending on fuel pressure or
> does it run continuously once the engine is running?


The fuel pump runs continuously whenever the ECU is getting timing pulses
from the distributor.  It pumps a minimum of sixty liters (one tank full)
through the system every hour.   It is the job of the pressure regulator to
maintain pressure in the fuel ring at 2.5 bar (36 psi) over the pressure in
the intake manifold at any given moment.  However this has little effect on
the total volume of fuel pumped through the system and back to the tank.

Yrs,
d