Date:         Fri, 15 Sep 1995 06:39:26 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         mtooley@indirect.com (Matt Tooley)
Subject:      It Pings...It Pings...finally

My Vanagon finally pings.  After struggling with the fuel injection system 
on my '80 Vanagon for the past two weeks I think I finally got it fixed.  It 
had been running rich (very rich).  Rich enough that it would die when 
starting from a dead start after it gotted warmed up.  It was behaving like 
it was flooded.

The first go around with this I had determined my temperature sensor from 
the cylinder head was giving erratic readings to the computer.  So I 
replaced it ($44) and things seem to work pretty good.  So I proceeded to 
drive it to Sante Fe (600 miles from Phoenix AZ) for the labor day weekend.  
When we got there it started doing this again along with missing while going 
down the highway.  So I thought something else in the FI system must have 
gone out.  So I checked everything the best I could with the limited tools 
that I had.  No luck finding anything...

When I got it home I again started checking out the FI system as described 
in the Bentley book and the Bosch FI book.  I checked the air flow meter, 
cold start valve, fuel pressure, fuel injectors, thermo time switch, and aux 
air regulator.  The air flow meter looked worn and was giving some high 
resistance readings at the idle end of the scale so I replaced it with a 
rebuilt unit.  Still no change.

So when I was messing with it after I put the new air flow meter on I 
wondered what would happen if I just grounded the lead to the computer that 
goes to the temp sensor.  It should make the motor think it is running hot 
(ie lean it out).  I did this and things seem to get better.  When I take it 
off ground it would die just like it did when attached to the temp sensor.  
Well it was getting dark, but at least I was on to something.

I figured it had to be the sensor, the ground strap to the motor, or the 
conductivity between the sensor and the head.  So when I got home last nite 
I got my ohm meter out and rang out the FI harness.  Everything looked good 
until I got to the temp sensor.  It read 8K ohms.  It is only suppose to be 
2k-3k at 68' F.  Well I live in AZ and its never 68'.  The resistance was 
suppose to be 800-900 ohms.  So I proceeded to find the cause of this.  It 
turned out to be bad conductivity between the sensor and the cylinder head.  
It must of built up some corrision on the drive to Sante Fe.  How and why I 
don't know?

Anyway,  after fixing the problem it now doesn't run rich.  Now all I have 
to do is get the fuel/air mixture and timing right to get it to stop pinging.  

Hopefully it will pass the emissions test this month.  I have enough 
receipts now for a few waivers.

Does anybody have any ideas as to why the resistance between the cylinder 
head and the head temp sensor would go up?  Could this happen if it wasn't 
screwed in tight enough?  The Haynes book talks about a rubber gasket or 
seal for the sensor, does anybody know anything about this?

Matt