Date: Fri, 6 Apr 2001 18:32:50 -0400
Reply-To: 72510.1173@COMPUSERVE.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Helen Fahy <72510.1173@COMPUSERVE.COM>
Subject: Wet weather power loss
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I know old problem, RTFA. I did that already. Kind of a pain as
www.vanagon.com. is down. I used the listserv search technique. Thanks
Jennifer!
Executive Summary: Is there a reference that describes how the digifant
system really works and not just test this and replace that?
Long Winded discussion:
I am trying to understand the relationship between the tachometer display
and the loss of power and the physical devices in the ignition system.
During the power loss on my '87 Westy the following events/observations are
common to all occurrences:
wet weather, though it does not have to be actually raining, it can occur in
heavy fog.
tachometer is being driven, of course the engine is slowing down, but there
is nothing erratic about the motion of the tach needle.
engine and oil temp are needle blade below led and ~185+ respectively
turning ignition switch off an on brings back normal engine performance for
a short time <<<Why does this work and is this the key to the analysis of
the problem???>>>
flooring throttle pedal will give a brief "burst" :() of power, at least
relatively
Some component details: the O2 sensor and AFM are new Bus Depot components
with less than 5K miles, new fuel pump output filter, plugs, cap and wires
<1K miles and capacitor wired across AFM in boot of connector for a few
years now.
I have disconnected the O2 sensor shielded wire, but I have not rung it out
with an ohmmeter. I disconnected this lead today prior to driving in the
rain, electrical taped the blade connector and tie wrapped it out of the
way. The van ran great for ~ 1 hour, then the 4 to 5 minute cycle of power
loss and restore via toggling the ignition switch off then on while rolling.
But if the shield is "close" electrically to the signal wire, the extra
moisture( rain or fog) could complete the circuit.
I also tried jiggling the ignition switch key, I have no other keys on this
lightweight keyring. I could not cause the power loss.
From the archives, I am aware that the throttle switch has on occasion
shorted out while the actual throttle position was in a cruise position.
This was suggested to imitate the closed throttle fuel shutoff
condition<Posting number 82352, dated 18 Mar 1999 08:39:45>
I have also aware that the Hall sensor can also cause problems. I believe
that when this sensor fails the van is not down on power, but dead.
Then there is the VWoA "Replace the ECU" when that happens.
Sorry for being long winded, part of this is me thinking out loud. Is there
a reference that describes how the digifant system really works and not just
test this and replace that? With the age of these systems and some of the
weird failures I wonder if we are not seeing not one problem but two or
three, clouding the water.
Current plan of attack in order of most likely guilty:
1. Ring out the O2 lead<Bentley 24.62 ECU connector pins 2+13 >,
2. check the throttle sensor<Bentley 24.62 ECU connector pins 6+11>,
3. check Hall sensor Bentley 24.62 ECU connector 6+8 & 6+18>
4. Others?