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Analyzing Primary Ignition
A
Reality Check
Sorry, this paper is no longer available here. However, it is included as part of the much
more comprehensive Nerd III CD.
The focus of this
50+ page paper is on how to analyze and pinpoint the cause of one of the most
common failures that result in serious drivability problems. A weak spark can cause a host of complaints,
from a no-start to a minor hesitation.
It can set any combination of misfire codes on OBD II as well as other
spin off effects and management issues.
Identifying the issue is not that difficult, but the causes can be
varied and a reliable method of diagnosis that is not vehicle or system
specific is needed.
We will answer
the following questions:
·
How can we use the lab scope to verify and analyze
primary?
·
What tests and observations are the most efficient
use of time?
·
How can we interpret what we see, and draw valid
conclusions?
There
has been much frustration and misdiagnosis related to attempts to draw
diagnostic conclusions from the primary current 'ramp'. This article will
illustrate the pitfalls of current 'ramp' diagnosis as we go back to the basic
physics and gain an understanding of some of the complex dynamics of coil
behavior.
There are
several ways to approach coil primary analysis. Some are more likely to lead to misdiagnosis than others. There has been much focus on the primary
current ramp qualities. The shape and
rise of the ramp directly represent the primary coil inductance. Since the primary inductance is a dynamic
thing, so also is the primary current ramp.
The shape and rise of the ramp is affected by internal coil induction
dynamics. Defects in the coil, as well
as outside environmental changes can have dramatic effects on the ramp. So, a ‘defective’ induction ramp could have
nothing to do with a coil problem.
Furthermore, a ‘normal’ current ramp does not mean the ignition coil is
good. Coils can fail in many ways, and
loss of primary coil induction is only one of them. We will cover the physics that govern some of the ignition coil
behavior to gain a deeper understanding and provide a more reliable diagnostic
method that is based on the physical laws.
If we are going to use something for diagnosis, it needs to be more
universal. It needs to be independent
of application and equipment variances, as much as possible. A reliable diagnostic technique should leave
few questions unanswered.
We will present a method that can be used on any inductive discharge coil
system that is firmly founded in the physics. We will also cover common
instrumentation issues that can disrupt our diagnostic process.
Why do you need
this paper? Put simply, to make your
coil diagnostics more reliable. The
small cost of this paper will come back to you many times in more efficient
diagnosis. This paper is a
comprehensive analysis of complex issues written for the automotive tech. As usual, in the Autonerdz tradition,
practical application is the goal. Simple,
reliable techniques are presented which can be used on any ignition coil
system.
Sorry,
this paper is no longer available here.
However, it is included as part of the much more comprehensive Nerd III CD.
Tom Roberts
Autonerdz.com
PO Box 810
East Olympia, WA 98540
360-455-9130
877-628-4899 toll free