Peak-n-hold failure!

[Mike Pitts]

BobR. wrote:
>Ain't that a great feeling! Sometimes things go right...

then Doc wrote:
>I'm jealous.........

Now for the let down.  I went to go test drive the modified 
ECM and as soon as I revved it once in the driveway, billows 
of raw fuel smoke started emanating from the exhaust.

A post mortem shows that two drivers failed with their outputs 
going nearly to ground (147 ohms on one, 13.4k ohms on the 
other).  All other drivers are > 3 megohms.  These two drivers 
were holding their respective injectors open 100%.

Soooo, I wonder if it's because of the way the ECM shares 
one zener between all drivers, isolated by diodes facing the 
opposite way?  Is there more flyback current when using peak 
and holds?  I wouldn't think so.  The input signal is a nice 5v 
square wave just like it's supposed to be, so I can't imagine 
that did the damage.

I guess the next step is replace the two failed drivers and 
modify the circuit with separate zeners on each driver.

At least the only smoke this time was all out of the exhaust. 8-)

-Mike