Date:         Tue, 26 Mar 2002 12:11:02 -0800
Reply-To:     Jack Pronovost <jackpron@AWESOMENET.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jack Pronovost <jackpron@AWESOMENET.NET>
Subject:      highway Dyno
Content-Type: text/plain; charset="iso-8859-1"

Hi
    Forgot to mention on previous post how I made my diagnostic, and since this might usefull to others, here it is. I needed to see what the ECU was doing when it would temporarily fail on the highway. I spliced two wires onto the two injector supply wires at the outlet of the ECU, The heavy white and heavy red and white. The signal is a series of square wave pulses with varying pulse width (duty cycle) to match engine fuel requirement. I hooked an analog DC meter with a scale of 0-10 volts. The meter averages the pulses to read an average DC value. At full duty cycle the meter reading is 10 volts and half duty cycle is 5 volts and so on. This becomes a fuel delivery meter expressed in % of full delivery such as 5 volts is %50, 2.5 volts %25 etc. At 50 to 60 Mph, the meter reads %30 to %40. However When the problem would occur I would get spikes of %70 or %80 on the meter with the usual bucking sputtering, and then the meter would return to normal for a while. Replacing the AFM  had no effect and left me with no other choice then to replace the ECU. Problem solved.   Jack