Model T Electronically Cranked Coil Tester
V12 ©2019 Mictel LLC
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4.4.2 Coil Test Results
The coil dwell time to fire and firing current must be within acceptable ranges for the coil to be
considered acceptable for use. The dwell time to fire value is displayed on the top scale of the
LED meter as Timing Error relative to a nominal value of 0 crank shaft degrees at 1000 RPM.
The possible coil test results are as follows:
Result Timing Error (Deg) Coil Current
Excellent 0 Ideal firing range
Good 0 +/- 1 Within acceptable range
Poor 0 +/- 2 or more Outside acceptable range
Table 2. Coil Test Results
IMPORTANT! – Good or Excellent Timing Error readings can still have a test result of Poor if
the coil firing current was outside the acceptable range. The Poor (Red LED) indicator will be
illuminated in this event even though Timing Error is 0 +/-1deg.
4.4.3 Coil Timing Error
The time required to charge the coil to the point of firing is known as dwell time to fire.
Nominal coil dwell time is 0.002 seconds (2ms) operating on 12VDC. This dwell time is
translated to ignition Timing Error and displayed on the ECCT lower scale calibrated in crank
shaft degrees with center value set to the nominal dwell time labeled as 0 degree Timing Error.
The scale is in 1 degree per division at 1000 RPM engine operation. The acceptable range of
Timing Error is 0 +/- 1 degree. Coils with Timing Error outside this range require adjustment
of the coil points covered in the next section.
4.4.4 Coil Point Adjustment
The coil dwell time to fire is determined by many variables. The main variables are:
1. Vibrator Spring Tension
2. Cushion Spring Tension
3. Cushion Spring Travel
4. Point Gap
Attaining the desired dwell time to fire and firing consistency depends upon setting these 4
variables in the proper proportion with respect to each other. The ECCT coil test quickly
displays the Timing Error for a given set of these 4 variables. It is up to the operator to know
which of these variables to adjust to achieve the desired Timing Error and firing consistency.
Note that these 4 variables interact with each other which sometimes makes coil point adjustment
challenging to achieve the desired performance. Coil point adjustment requires patience and
experience for these reasons. It is highly recommended that new coil points be used when first
learning how to adjust and balance these 4 variables to achieve the desired result by avoiding
introduction of still more variables such as contact resistance and pitting. The next section
provides an introduction to the basics of coil point adjustment.
