Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (September 1999, week 4)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Fri, 24 Sep 1999 19:48:53 -0400
Reply-To:     John <johnpatt@WARWICK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John <johnpatt@WARWICK.NET>
Subject:      Digijet troubleshooting - (very long & technical)
Comments: To: "Osterwald, Ray" <t4504@PSCO.COM>
Content-Type: text/plain; charset=iso-8859-1

Osterwald, Ray wrote: > > Hello to everyone, > I’ve been fighting a problem with my ’84 water-cooled 1.9 (156,000 miles) for about 6 months now.

Hi Ray,

I'm not an expert on Vanagon Digijet systems but I think the source of your problem is likely the source of many Digifant complaints as well.

While your VW technician has surely tried and you have paid $$$, there is a serious absence of TEST results. It's one thing to install parts & try fixes for other engine management systems but it is simplier to look at the information that the Digijet control module (DCM) uses to decide how much fuel to inject into the engine under the prevailing conditions.

In the case of the Digijet system, its important to recognize what the DCM really is. Its a glorified, goddamn voltmeter that decides ONE thing - how long to power the injectors open by grounding the injectors negative terminal ! If the DCM can look at specific voltages values and decide rich or lean, we with the help of a DVOM, can look at those same values and find the information that is causing your new DCM to inject too much fuel. Selling this Vanagon for this complaint after all the money you have invested would be a real tragedy ! The fact that the vehicle is operated at high altitude means that this is probably not a large problem. At high altitudes a small injector opening error can cause your complaint. However the fact that the primary symptom completely vanishes after a hot restart certainly "thickens the stew" !

Please look at these questions and ask yourself if these test values have been checked and recorded somewhere. If not, why were the associated components replaced ? Each one of these input values when wrong can lead to the DCM injecting the incorrect amount of fuel.

1) What is the normal DCM power supply voltage and what is the voltage when the symptom is present ?

2) What is the normal fuel line pressure and what is the pressure when the symptom is present ?

2) What is the air flow meter normal load signal (say at idle) to the DCM and what is it when the symptom is present ?

3) What is the inlet air/coolant temp sensor full hot signal to the DCM and what is it when the symptom is present ?

4) What is the cranking enrichment(KL50) signal to the DCM when running normally and what is it when the symptom is present ?

5) What is the VOLTAGE DROP VALUE (VDV) of all DCM ground circuits (B-) normally and what is the B- VDV when the symptom is present ?

6)What is the O2 sensor signal voltage normally and what is it when the symptom is present ?

If these tests seem really basic & repetitive, they are. These questions simply look at the same voltage values that drive the DCM to open the injectors. Be a detective and look for the same information (while troubleshooting) that the DCM uses to compute injector opening time and you'll find the reason for the extra fuel injection enrichment.

I could have included a lot additional basics, test values and pin numbers but this message is too busy & too long already. See the Bentley manual, that's where I get my information !

Good luck, JP


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.