Date:         Sun, 27 Apr 2014 19:03:25 -0700
Reply-To:     Don Hanson <dhanson928@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Don Hanson <dhanson928@GMAIL.COM>
Subject:      Digifant question...fuel pump effect?
Content-Type: text/plain; charset=UTF-8

  Ok, dumb question here...

   My fuel pump has been really noisy for about 1500 miles now and I just
replaced it with a new one...A quiet one...

   Now,  with the noisy one, the van ran OK....no glaring issues with it's
digifant inline four motor....I did 'sense' a slight hesitation as I
accelerated from coasting...I think....and sometimes as I went from no
throttle to throttle, like at the bottom of a gully, there was a big
hesitation, like the motor was OFF for a second or two, then pretty normal
again...
   I think this slightly "off" behavior has all gone away with the new pump
installed..I could be imagining it but the motor seems to run better now.

   So I was under the impression that the fuel pumps in our digifant VWs
supply way more than enough fuel to the injectors and some of it is always
run back into the tank as extra......I assume the noisy old pump was
supplying enough fuel...I drove back from California to Wa.  with a 5000lb
loaded van up highway 395, through the High Sierras without any
issues....pump whining away! (spare one under the rear bench seat)   But is
it possible the noisy pump was making the engine run less perfect?
 I should know, but how does the digifant fueling system actually work?
Could the old noisy pump be supplying inadequate fuel pressure and volume,
just by a little?   It seemed to not matter how much throttle I was
using...the van ran fine, but just whining and noisy...

  Anybody want to give the short version of how this stuff actually works?
I'm sort of familiar with Motronic, but I never bothered to do anything but
drive my Digifant inline...I guess I should learn HOW it does it's thing....

  Thanks, Don Hanson