Engine - Miss/Backfire/Hard Start/Hesitation or Stall
Number: 87-145Section: 6D
Date: MAY, 1987
Subject: ENGINE MISS, BACKFIRE, HARD START, HESITATION OR STALL
Model and Year: 1986-87 MODELS WITH DELCO C I "TYPE II"
AND "DIS" IGNITION SYSTEMS
TO: ALL CHEVROLET DEALERS
Whenever a complaint of "engine miss, stall, hesitation, backfire or cranks but will not start" is encountered on these types of ignition systems, the resistance of the secondary windings of the individual coils should be measured first.
Coil resistance can be accurately measured using the Kent Moore High Impedance Digital Volt Ohm Meter #J34029-A or equivalent. Set the meter on the 20k scale and measure the resistance across the coil towers with the spark plug wires removed. The resistance of the coil may have to be measured both hot and cold as some coils show an acceptable reading cold.
FIGURE 1 - Type II "DIS" Coil:
"Type II"/"DIS" coils (see Figure 1) should be replaced whenever they measure lower than 5000 ohms or greater than 7000 ohms. They would display 5.0 to 7.0 on the meter. An "open" coil will read "OL" and should be replaced. This type of coil can be removed from the module and is serviced separately. The correct part number for a "Type II"/"dis" coil is #10497771 and can be found in Group 2.170 in the parts catalog.
FIGURE 2 - Type I Coil:
"Type I" coil (see Figure 2) resistance does not apply to the above specifications or conditions.