Date:         Wed, 30 Mar 2016 20:38:07 -0400
Reply-To:     Ed McLean <email99@BELLSOUTH.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Ed McLean <email99@BELLSOUTH.NET>
Subject:      Re: Engine Cranks but No Start

Scott's diagnostic method will certainly determine if the ECU is
functioning well enough to trigger the fuel injectors but it won't
identify the reason.


I wrote a note to the list on December 12, 1995 at 1:19am (title RE:no
start, email address mcleane@nando.net) describing my experience with a
weak battery.  On reading it again I see that the ignition system and
starter worked but the fuel injection didn't when the voltage at the
battery was slightly below 10.5 vdc.  I remember doing the following
diagnostic experiment to determine the actual voltage threshold for my
'86 ECU.

The starter would spin the engine but it wouldn't start.  After
attaching my small gauge jumper cables and allowing the vanagon battery
to be charged by the helper car the engine would start with the jumper
cables removed.  The voltage at the battery during starting was about 11
vdc. I turned off the engine and was able to restart with a voltage of
about 10.8 vdc.  I then turned off the engine and turned the ignition
and headlights on for about a minute to drain the battery and then
turned off the headlights.  I then tried to start the engine with no
success.  The battery voltage was 10.2 vdc while the starter was turning
over the engine.  I finally hooked the jumper cables back up and tried
to start the engine several times with short charging periods between
trys.  I monitored voltage at the battery while the starter was turning.
The engine would not start until the battery voltage climbed to above
10.5 vdc.

I remember this very clearly because I thought it was interesting to be
able to determine the fuel injector system voltage threshold precisely
with a very simple experiment.

All always, your mileage may vary, or in this case, your voltage may
vary.

Of course, all this may have nothing to do with Wrenold's starting
problem but trying some jumper cables even if the starter works is worth
trying.  Poor electrical connections and grounds may also cause a no
start conditions.

Ed