On Sun, 17 Oct 2004 18:51:10 -0500, Mark Leininger
wrote:

I have a 92 dodge dakota with the symptom that when the engine gets warm
it loses spark. I have the manual and have followed the diagnostic
procedure to the point where I need to test the output from the ECM. On
this model, pin 19 of the ECM controls the ground to the ignition coil
to fire the plugs at the proper time. The manual says something to
diagnose this that I can't understand. They say to make a little jumper
with a 33uf capacitor that is used to ground pin 19 and ground the coil.
When the ground is removed, if a spark is seen at the coil cable (I
assume they mean secondary), they say the ECM is bad.

Can someone explain the logic of what I'm trying to do. I understand
what the ECM is supposed to do, but I don't understand how to know if
it's doing it, even with this little jumper gizmo they describe. I'm
fairly electronics literate, but not a wiz.

There are no stored error codes at any point in the failure that I have
been able to observe. All help appreciated
thanks


You're just manually triggering the coil to verify the wiring to the
coil and the coil itself aren't bad. Not a great test, really. An
oscope on on the ecm output would be your best way to look at this. A
multimeter could be useful if it showed duty cycle, but even ac
voltage would be an indicator that something is pulsing.

Personally, for intermittent problems when it's warm I would suspect a
bad coil. Next culprit would be the pickup sensor. Either a crank or
distributor. Not sure what your Dodge has. If the rpm guage is
dropping to zero when the engine is still turning, I would lean toward
a sensor problem.

The Jeep engines are notorious for bad crank position sensors causing
intermittent no spark problems when warm. No codes are usually set
when this happens.


-Chris