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PostPosted: Fri Jun 06, 2008 4:39 pm 
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Retired Admin/Techinfo Admin

Joined: Mon May 19, 2008 2:08 pm
Posts: 25729
Location: Space Coast, or at least it used to be
Year and Trim: 03 SLE, 95 SE, 95 TS SE
Author : Gearhead Team

Symptoms of a bad coil can include one or more of the following: hard start, misfire, stall. Symptoms may be affected by outside temperature or engine temperature. Mismatched coils can cause a rough idle. This can sometimes also be apparent while cruising in overdrive at a low RPM, particularly on a low climbing hill (under load with light throttle).

WARNING! Yellow Accel brand (aftermarket) coils have performed poorly in the experience of Bonneville Club members and are NOT recommended.

The coil pack is made up of three individual coils that each fire two spark plugs. Each coil is made up of primary windings and secondary windings. In a new coil pack, the resistance readings of all primary windings should be nearly identical,and the resistance readings of all secondary windings should be nearly identical. A reading of infinite resistance (open) or no resistance (short) indicates a bad coil.

Resistance of the secondary windings can be measured with the coils in place, but you'll need to remove the coils from their mountings to test the primary windings.

Before you begin, make sure all spark plug wires are clearly marked with the correct cylinder number and connected to the proper coil terminal. Remove and replace wires one coil at a time to minimize the chance of misconnecting wires.

Check the resistance of each secondary winding by removing the plug wires placing the ohm meter probes on the plug wire terminals for each coil as follows: terminals 1 and 4; terminals 2 and 5; and terminals 3 and 6.

Testing Magnavox Coil Pack Secondaries:
Image

Testing AC Delco Type II Secondaries:
Image

The resistance readings for all three secondary windings should be similar to each other and within the ranges shown in the table below.

Check the resistance of each primary winding by first removing the bolts attaching the coil to the ignition control module (ICM), then wiggling and pulling the coil(s) up off the terminals on the ICM. Magnavox combines all three coils in a single plastic casting that must be removed and replaced as a unit. Others can be removed individually. Place the ohm meter probes on the two connectors for the primary winding on the underside of each coil.

Testing AC Delco Type II Primaries:
Image

The resistance readings for all three primary windings should be similar to each other and within the ranges shown in the table below.


Year….Manufacturer….Engine RPO…..Primary (ohms)……… Secondary (k-ohm)

86-91......Magnavox.....…......LN3..……......0.5-0.8.....….……………....9.0-12.0

91-92.5...Magnavox.…….......L27......……..0.5-0.8....………….…….....9.0-12.0

92.5-94....Delco.…….............L27......……. 0.5-0.9....…………..……......5.0-8.0

92-95…....Delco.…….............L67……...…..0.5.-0.9....………………......5.0-8.0

96-99…....Delco.…….............L67……...…..0.5-0.9.………………..........5.0-8-0

95-99…....Delco..…................L36....……….0.5-0.9....………………........5.0-8.0

86-99.........MSD*.....................ALL...................0.35........................................7.8

* MSD data as specified by manufacturer.


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