Date:         Tue, 25 Feb 1997 08:56:59 -0500
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Jeff Diebolt <jdiebolt@up.net>
Subject:      Re: Diaganosing Fuel Injection Systems

Fuel injection is actually a very simple system. Although troubleshooting
it can sometimes get difficult. The ECU relieves information from the
temperature sensor, oxygen sensor, air flow sensor, coil and throttle
switches. I am not familiar with all the components on the Vanagon any
more. With this information it adjusts the duration of the injector firing
for proper mixture. The coil wire is only to tell where the distributor is
firing at and nothing else. The fuel injection does not use the coil signal
for anything else but that. It need to know when the plugs are firing so it
can know when to deliver the fuel. The other stuff is for the rest of the
mixture adjustments. There is a tap somewhere in the engine compartment for
checking fuel pressure, get yourself a gauge and check it, this is a guess
but I think it's somewhere around 30PSI. Also I believe your engine has a
cold start valve, that's probably where you're getting the smell from. But
by the same token it should fire on that bit of fuel and quit. So you
should also check the spark to the plugs. Either pull out a plug or use an
old one and check the spark right at the plug. Make sure it's getting where
it needs too. Just a few quick suggestions. Good Luck
>At 11:51 AM 2/24/97 -0600, vince_pappalardo@om.cv.hp.com wrote:
>       Here are some basic questions I am trying to find out:
>     1) What systems control the fuel mixture (airflow meter?, does the ECU 
>     control only the spark and timing or is it also tied into the 
>     injection system)?
>     2) How do you determine if the injectors are working properly (I did 
>     not want to explore this on the side of the road with a hot engine!)
>     3) What methods, tools, and tricks are known to help when diagnosing 
>     VW FI systems.
>       Any help finding faqs info on these subjects or direct responses to 
>     the problem would be appreciated.
>     
>     TIA,
>     
>     Vince


 Greetings from Michigan's Upper Peninsula
 Jeff & Jean-Marie Diebolt
 mailto:jdiebolt@up.net